2024/07/19 更新

写真a

ササキ ケイコ
笹木 圭子
所属
理工学術院 創造理工学部
職名
教授
学位
博士(工学) ( 北海道大学 )
メールアドレス
メールアドレス

学歴

  •  
    -
    1982年

    北海道大学  

委員歴

  • 2023年10月
    -
    継続中

    日本学術会議  会員

  • 2012年04月
    -
    継続中

    JST  戦略的国際科学技術協力推進事業 日本ー中国(NSFC)研究交流課題 審査委員

  • 2008年04月
    -
    継続中

    独立行政法人 石油天然ガス・金属鉱物資源機構  技術委員

  • 2007年04月
    -
    継続中

    文部科学省科学技術政策研究所  専門調査委員

  • 2006年04月
    -
    継続中

    独立行政法人新エネルギー・産業技術総合開発機構NEDO  技術委員

  • 2005年04月
    -
    継続中

    福岡県環境審議会  福岡県環境審議会委員

  • 1999年
    -
    継続中

    資源・素材学会  常議員

  • 2018年04月
    -
    2023年09月

    日本学術会議  連携会員

  • 2022年04月
    -
    2023年03月

    資源・素材学会  副会長

  • 2021年02月
    -
    2022年01月

    資源・素材学会  九州支部 支部長

  • 2018年02月
    -
    2019年01月

    資源・素材学会  副会長

  • 2017年02月
    -
    2019年01月

    資源・素材学会  編集委員長

  • 2017年01月
    -
    2018年12月

    国際科学技術財団  日本国際賞審査委員

  • 2014年01月
    -
    2015年12月

    国際科学技術財団  日本国際賞審査委員

  • 2011年04月
    -
    2013年03月

    日本学術振興会  審査委員

  • 2007年04月
    -
    2009年03月

    日本学術振興会  審査委員

  • 2005年04月
    -
    2006年03月

    環境省  環境審議会 瀬戸内部会

  • 2002年
    -
     

    日本廃棄物学会  幹事

  • 1999年
    -
     

    日本分析化学会  幹事

▼全件表示

所属学協会

  •  
     
     

    日本腐植物質学会

  •  
     
     

    日本廃棄物学会

  •  
     
     

    日本分析化学会

  •  
     
     

    資源・素材学会

  •  
     
     

    Geochemical Society

  •  
     
     

    米国化学会

▼全件表示

研究分野

  • 地球資源工学、エネルギー学 / 宇宙惑星科学 / 環境政策、環境配慮型社会 / 環境影響評価

研究キーワード

  • 炭素材料

  • 光触媒

  • 粘土鉱物

  • 環境材料

  • バイオハイドロメタラジー

  • ナノジオサイエンス

  • 共沈

  • 吸着

  • 生体鉱物

  • 資源再生

  • 生物的環境修復

  • Biomineralization

  • Resource Recycling

  • Bioremediation

▼全件表示

受賞

  • 論文賞

    2018年03月   資源・素材学会  

    受賞者: 笹木 圭子

  • 研究活動表彰

    2013年12月   九州大学  

    受賞者: 笹木 圭子

  • 研究活動表彰

    2012年12月   九州大学  

    受賞者: 笹木 圭子

  • 研究活動表彰

    2011年12月   九州大学  

    受賞者: 笹木 圭子

  • 論文賞

    2011年03月   資源・素材学会  

    受賞者: 笹木 圭子

  • 論文賞

    2009年03月   資源・素材学会  

    受賞者: 笹木 圭子

  • 論文賞

    2008年03月   資源・素材学会  

    受賞者: 笹木 圭子

  • 資源・素材学会賞奨励賞

    1998年  

▼全件表示

メディア報道

  • ダイバーシティニュース

    九州大学男女共同参画推進室   ダイバーシティニュース  

    2017年12月

 

論文

  • Exploring the Potential of Copper Palladium Nanocube Electrocatalysts for Enhancing the Overall Water Splitting Performance

    Brahmari Honnappa, Manova Santhosh Y, Sulakshana Shenoy, Chitiphon Chuaicham, Yuto Noguchi, Keiko Sasaki, Karthikeyan Sekar

    Energy & Fuels    2024年04月

    DOI

    Scopus

  • Enhancing photocatalytic efficiency: Geopolymer-supported TiO2 composites for sustainable organic pollutant degradation

    Changshuai Chen, Sulakshana Shenoy, Chitiphon Chuaicham, Jirawat Trakulmututa, Quanzhi Tian, Haijun Zhang, Keiko Sasaki

    Optical Materials    2024年04月

    DOI

    Scopus

  • Nanoarchitectonics Design Strategy of Metal–Organic Framework and Bio-Metal–Organic Framework Composites for Advanced Wastewater Treatment through Adsorption

    Nithish Agamendran, Maseed Uddin, Manova Santhosh Yesupatham, Mariyappan Shanmugam, Ashil Augustin, Tanay Kundu, Ramani Kandasamy, Keiko Sasaki, Karthikeyan Sekar

    Langmuir    2024年02月

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Mechanical activation of coal gasification slag for one-part geopolymer synthesis by alkali fusion and component additive method

    Changshuai Chen, Sulakshana Shenoy, Yinhai Pan, Keiko Sasaki, Quanzhi Tian, Haijun Zhang

    Construction and Building Materials    2024年01月

    DOI

    Scopus

    6
    被引用数
    (Scopus)
  • Effect of oxidation treatment on the selective separation of molybdenite from chalcocite using flotation

    Daniyarov Berdakh, Hajime Miki, Tsuyoshi Hirajima, Keiko Sasaki, Akbarshokh Ulmaszoda, Ryota Nakao, Daishi Ochi, Yuji Aoki, Gde Pandhe Wisnu Suyantara

    Powder Technology   431  2024年01月

     概要を見る

    Molybdenite is associated with primary and secondary copper sulfide minerals. Few studies have focused on the selective flotation of molybdenite to separate it from secondary copper sulfide minerals, such as chalcocite. This study evaluated the use of oxidation treatment to separate molybdenite from chalcocite. The effects of oxidation treatment with hydrogen peroxide (H2O2) on the flotation behaviors of molybdenite and chalcocite in the presence of collectors (i.e., potassium amyl xanthate and diesel oil) were evaluated, and the impacts of H2O2 concentration, oxidation treatment duration, and pH level were assessed. Chalcocite flotation tests showed that the H2O2 treatment significantly reduced the recovery of chalcocite due to the formation of copper hydroxide and sulfate species on the chalcocite surface, which altered its surface hydrophobicity. On the other hand, the low surface oxidation of molybdenite led to high flotation recovery after the oxidation treatment. Oxidation treatment with a 10 mM H2O2 solution at a pH of 9 for 20 min resulted in a separation efficiency of 87%, with 98% molybdenite recovery and 11% chalcocite recovery. The results show that H2O2 oxidation treatment enables the selective flotation of molybdenite to separate it from chalcocite.

    DOI

    Scopus

    5
    被引用数
    (Scopus)
  • 3D/2D photocatalyst fabricated from Pt loading TiO2 nanoparticles and converter slag-derived Fe-doped hydroxyapatite for efficient H2 evolution

    Kaiqian Shu, Chitiphon Chuaicham, Keiko Sasaki

    Chemical Engineering Journal    2023年12月

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Fabrication of one-part geopolymer from coal gasification slag via alkali fusion and component additive method: Effect of different alkali-to-slag ratios

    Changshuai Chen, Keiko Sasaki, Quanzhi Tian, Haijun Zhang

    Journal of Building Engineering    2023年12月

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • Sodium metabisulfite as a copper depressant in the selective flotation of copper-molybdenum concentrate using seawater

    Gde Pandhe Wisnu Suyantara, Hajime Miki, Daishi Ochi, Yuji Aoki, Kumika Ura, Daniyarov Berdakh, Akbarshokh Ulmaszoda, Eska Putra Dwitama, Keiko Sasaki, Tsuyoshi Hirajima

    Advanced Powder Technology   34 ( 12 )  2023年12月

     概要を見る

    The main challenge for the selective flotation of copper and molybdenum (Cu-Mo) sulfide minerals in seawater is the formation of colloidal precipitates in strongly alkaline conditions. These precipitates hinder the selective separation of copper from molybdenum minerals in seawater by lowering the floatability of Cu-Mo sulfide minerals. The present study aimed to examine the direct utilization of seawater in the selective flotation of Cu-Mo sulfides. Additionally, the effectiveness of sodium metabisulfite (Na2S2O5) as a copper depressant for selective flotation of Cu-Mo sulfides in seawater was studied under weakly acidic, neutral, and moderately alkaline conditions. A complex Cu-Mo concentrate that largely consisted of chalcopyrite and molybdenite, as well as a tiny amount of pyrite and quartz, was used in the flotation tests. The flotation results revealed that treatment with 3.6 kg/t Na2S2O5 in seawater at pH 5.5 significantly lowered the copper recovery from 97% to 11% and caused a modest reduction in the molybdenum recovery from 98% to 94% with a Cu-Mo separation efficiency of 83%. These flotation results demonstrate that Na2S2O5 treatment in seawater selectively depresses the floatability of copper minerals. Consequently, molybdenum can be separated from copper minerals under a weakly acidic condition in seawater. In addition, this study discusses the effects of various pH conditions and dosages of Na2S2O5. The surface properties of Cu-Mo minerals were studied using X-ray photoelectron and infrared spectroscopies, and a mechanism to explain the selective flotation of Cu-Mo using Na2S2O5 treatment in seawater is proposed.

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Tailoring Interfacial Physicochemical Properties in Cu2O-TiO2@rGO Heterojunction: Insights from EXAFS and Electron Trap Distribution Analysis

    Sulakshana Shenoy, Chitiphon Chuaicham, Mariyappan Shanmugam, Takamasa Okumura, Umamahesh Balijapalli, Wei Li, Vellaichamy Balakumar, Keiko Sasaki, Karthikeyan Sekar

    ACS Applied Materials & Interfaces    2023年11月

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • Fe-Loaded Montmorillonite/TiO2 Composite as a Promising Photocatalyst for Selective Conversion of Glucose to Formic Acid under Visible-Light Irradiation

    Assadawoot Srikhaow, Li Zhang, Chitiphon Chuaicham, Jirawat Trakulmututa, Sulakshana Shenoy, Keiko Sasaki

    Crystals    2023年11月

    DOI

    Scopus

  • Fe-Loaded Montmorillonite/TiO2 Composite as a Promising Photocatalyst for Selective Conversion of Glucose to Formic Acid under Visible-Light Irradiation

    Assadawoot Srikhaow, Li Zhang, Chitiphon Chuaicham, Jirawat Trakulmututa, Sulakshana Shenoy, Keiko Sasaki

    Crystals    2023年11月

    DOI

    Scopus

  • Nitric oxide removal by synergistic photooxidation and adsorption using Pd1/g-C3N4-UiO-66-NH2 P-A heterojunction

    Jiayou Liu, Xiaoxiang Huang, Lizhen Hu, Penglei Liu, Liuhu Jia, Keiko Sasaki, Zhongchao Tan, Hesheng Yu

    Chemical Engineering Journal    2023年11月

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • The Role of Mg Doping in Manipulating the Adsorption Mechanisms of CaAl-Layered Double Hydroxide: Investigating the Effects of Calcination Temperature and Borate Concentration Changes

    Shuang Xu, Binling Guo, Keiko Sasaki, Xinhong Qiu

    Minerals    2023年10月

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Effect of Alkali Fusion Methods on the Preparation of One-Part Geopolymer From Coal Gasification Slag

    Changshuai Chen, Keiko Sasaki, Quanzhi Tian, Haijun Zhang

    ACS Omega    2023年10月

    DOI

    Scopus

    5
    被引用数
    (Scopus)
  • Atomic‐level investigation on significance of photoreduced Pt nanoparticles over g‐C3N4/bimetallic oxide composites

    Sulakshana Shenoy, Chitiphon Chuaicham, Karthikeyan Sekar, Keiko Sasaki

    ChemSusChem    2023年10月

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Charge transfer mechanism through S-scheme heterojunction in in-situ synthesized TiO2/Fe-doped hydroxyapatite for improved photodegradation of xanthate

    Kaiqian Shu, Chitiphon Chuaicham, Yuto Noguchi, Longhua Xu, Keiko Sasaki

    Journal of Hazardous Materials    2023年10月

    DOI

    Scopus

    6
    被引用数
    (Scopus)
  • Solar-light-driven photocatalytic conversion of monosaccharide by oxygen-doped graphitic carbon nitride/artificial steel converter slag composite

    Assadawoot Srikhaow, Chitiphon Chuaicham, Sulakshana Shenoy, Jirawat Trakulmututa, Keiko Sasaki

    Chemical Engineering Journal    2023年10月

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • Enhancement of Photocatalytic Rhodamine B Degradation over Magnesium–Manganese Baring Extracted Iron Oxalate from Converter Slag

    Chitiphon Chuaicham, Jirawat Trakulmututa, Sulakshana Shenoy, Vellaichamy Balakumar, Phatchada Santawaja, Shinji Kudo, Karthikeyan Sekar, Keiko Sasaki

    Separations    2023年08月

    DOI

    Scopus

  • Enhancement of Photocatalytic Rhodamine B Degradation over Magnesium–Manganese Baring Extracted Iron Oxalate from Converter Slag

    Chitiphon Chuaicham, Jirawat Trakulmututa, Sulakshana Shenoy, Dr. Balakumar Vellaichamy, Phatchada Santawaja, Shinji Kudo, KARTHIKEYAN SEKAR, Keiko Sasaki

    Separations    2023年08月

    DOI

    Scopus

  • Preparation of Iron Oxalate from Iron Ore and Its Application in Photocatalytic Rhodamine B Degradation

    Chitiphon Chuaicham, Sulakshana Shenoy, Jirawat Trakulmututa, Vellaichamy Balakumar, Phatchada Santawaja, Shinji Kudo, Karthikeyan Sekar, Keiko Sasaki

    Separations    2023年06月

    DOI

    Scopus

  • Z-scheme heterojunction of graphitic carbon nitride and calcium ferrite in converter slag for the photocatalytic imidacloprid degradation and hydrogen evolution

    Takumi Inoue, Chitiphon Chuaicham, Noritaka Saito, Bunsho Ohtani, Keiko Sasaki

    Journal of Photochemistry and Photobiology A: Chemistry    2023年06月

    DOI

    Scopus

    6
    被引用数
    (Scopus)
  • Preparation of Iron Oxalate from Iron Ore and Its Application in Photocatalytic Rhodamine B Degradation

    Chitiphon Chuaicham, Sulakshana Shenoy, Jirawat Trakulmututa, Dr. Balakumar Vellaichamy, Phatchada Santawaja, Shinji Kudo, KARTHIKEYAN SEKAR, Keiko Sasaki

    Separations    2023年06月

    DOI

    Scopus

  • Effect of hydrogen peroxide on selective flotation of chalcocite and enargite

    Gde Pandhe Wisnu Suyantara, Daniyarov Berdakh, Hajime Miki, Tsuyoshi Hirajima, Keiko Sasaki, Daishi Ochi, Yuji Aoki

    International Journal of Mining Science and Technology   33 ( 6 ) 703 - 716  2023年06月

     概要を見る

    Enargite is typically associated with chalcocite. Owing to the similarity in the flotation behaviors of these minerals, both minerals are reported to concentrate in the conventional flotation circuit. However, inorganic arsenic in enargite can decrease the copper concentrate quality and increase the operating cost of processing this concentrate. Separating these minerals is important for cleaner copper production to avoid these effects. In this context, this study investigated the effect of hydrogen peroxide (H2O2) treatment on the flotation behavior of chalcocite and enargite. Flotation tests of pure and mixed minerals indicated that H2O2 treatment reduced the floatability of chalcocite and enargite by forming sulfate and copper hydroxide on their surfaces. Despite the detrimental effect of the H2O2 treatment, there was a narrow window of H2O2 concentration for separating both minerals, in which enargite floated and chalcocite was depressed. This selective flotation behavior was caused by the rapid adsorption of potassium amyl xanthate (KAX) and lower surface oxidation of enargite compared with that of chalcocite.

    DOI

    Scopus

    6
    被引用数
    (Scopus)
  • Effect of goethite (α-FeOOH) nanoparticles on the surface properties and flotation behavior of chalcopyrite

    Gde Pandhe Wisnu Suyantara, Intan Nurul Rizki, Akbarshokh Ulmaszoda, Hajime Miki, Keiko Sasaki

    Journal of Environmental Chemical Engineering   11 ( 3 )  2023年06月

     概要を見る

    Chalcopyrite flotation is selectively depressed by oxidation treatment. The presence of ferric oxyhydroxide on the surface of chalcopyrite after oxidation treatment is a key factor in depressing chalcopyrite flotation. However, there is no concrete evidence that ferric oxyhydroxide has a depressing effect. In addition, the effectiveness of this depressing effect could be enhanced by directly applying ferric oxyhydroxide nanoparticles. This study investigated the effect of goethite (α-FeOOH) nanoparticles on the surface properties and flotation behavior of chalcopyrite. α-FeOOH nanoparticles were produced through chemical precipitation followed by hydrothermal treatment. The crystalline structure of irregular rice grain-shaped α-FeOOH nanoparticles was confirmed by the X-ray diffraction pattern and scanning electron microscope image. Micro-flotation experiments showed that chalcopyrite recovery decreased significantly from 93 % to 13 % when 30 mg/L α-FeOOH nanoparticles was used. This flotation result demonstrated the potential of α-FeOOH nanoparticles as a nanodepressant for the flotation of chalcopyrite. These nanoparticles physically adsorbed on the chalcopyrite surface and rendered its surface hydrophilic, thereby reducing the chalcopyrite flotation recovery. The attractive electrostatic force between the positively charged α-FeOOH nanoparticles and the negatively charged chalcopyrite surface is likely responsible for the adsorption of α-FeOOH nanoparticles on chalcopyrite.

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • Mixed-Phase Fe2O3 Derived from Natural Hematite Ores/C3N4 Z-Scheme Photocatalyst for Ofloxacin Removal

    Sulakshana Shenoy, Mohsen M. Farahat, Chitiphon Chuaicham, Karthikeyan Sekar, Boopathy Ramasamy, Keiko Sasaki

    Catalysts    2023年04月

    DOI

    Scopus

    5
    被引用数
    (Scopus)
  • Mixed-Phase Fe2O3 Derived from Natural Hematite Ores/C3N4 Z-Scheme Photocatalyst for Ofloxacin Removal

    Sulakshana Shenoy, Mohsen M. Farahat, Chitiphon Chuaicham, KARTHIKEYAN SEKAR, R. Boopathy, Keiko Sasaki

    Catalysts    2023年04月

    DOI

    Scopus

    5
    被引用数
    (Scopus)
  • Simultaneous Photocatalytic Sugar Conversion and Hydrogen Production Using Pd Nanoparticles Decorated on Iron-Doped Hydroxyapatite

    Chitiphon Chuaicham, Yuto Noguchi, Sulakshana Shenoy, Kaiqian Shu, Jirawat Trakulmututa, Assadawoot Srikhaow, Karthikeyan Sekar, Keiko Sasaki

    Catalysts    2023年03月

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • Simultaneous Photocatalytic Sugar Conversion and Hydrogen Production Using Pd Nanoparticles Decorated on Iron-Doped Hydroxyapatite

    Chitiphon Chuaicham, Yuto Noguchi, Sulakshana Shenoy, Kaiqian Shu, Jirawat Trakulmututa, Assadawoot Srikhaow, KARTHIKEYAN SEKAR, Keiko Sasaki

    Catalysts    2023年03月

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • In-situ hydrothermal synthesis of Fe-doped hydroxyapatite photocatalyst derived from converter slag toward xanthate photodegradation and Cr(VI) reduction under visible-light irradiation

    Kaiqian Shu, Chitiphon Chuaicham, Yuto Noguchi, Longhua Xu, Keiko Sasaki

    Chemical Engineering Journal    2023年03月

    DOI

    Scopus

    27
    被引用数
    (Scopus)
  • The Effect of Microwave Pre-treatment on the Magnetic Properties of Enargite and Tennantite and Their Separation from Chalcopyrite

    Ahmed M. Elmahdy, Hajime Miki, Keiko Sasaki, Mohsen Farahat

    Minerals    2023年02月

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • 2
    被引用数
    (Scopus)
  • Simple tactic polycondensation synthesis of Z-scheme quasi-polymeric g-C3N4/CaFe2O4 composite for enhanced photocatalytic water depollution via p-n heterojunction

    Sulakshana Shenoy, Chitiphon Chuaicham, Takamasa Okumura, Karthikeyan Sekar, Keiko Sasaki

    Chemical Engineering Journal   453   139758 - 139758  2023年02月

    担当区分:責任著者

    DOI

    Scopus

    41
    被引用数
    (Scopus)
  • Fabrication of Reduced Ag Nanoparticle Using Crude Extract of Cinnamon Decorated on ZnO as a Photocatalyst for Hexavalent Chromium Reduction

    Intan Nurul Rizki, Takumi Inoue, Chitiphon Chuaicham, Sulakshana Shenoy, Assadawoot Srikhaow, KARTHIKEYAN SEKAR, Keiko Sasaki

    Catalysts    2023年01月

    DOI

    Scopus

    5
    被引用数
    (Scopus)
  • Recent Clay-Based Photocatalysts for Wastewater Treatment

    Chitiphon Chuaicham, Jirawat Trakulmututa, Kaiqian Shu, Sulakshana Shenoy, Assadawoot Srikhaow, Li Zhang, Sathya Mohan, Karthikeyan Sekar, Keiko Sasaki

    Separations    2023年01月

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • Unveiling the bifunctional role of morphological differences of self-supported Cu(OH)2 in electrocatalysis

    Brahmari Honnappa, T. R. Naveen Kumar, Prince J. J. Sagayaraj, Sulakshana Shenoy, Chitiphon Chuaicham, Manova Santhosh Yesupatham, Anantharaj Sengeni, Bernaurdshaw Neppolian, Keiko Sasaki, Karthikeyan Sekar

    Journal of Materials Chemistry A    2023年

    DOI

  • Nitridation-free preparation of bimetallic oxide-nitride bifunctional electrocatalysts for overall water splitting

    Sulakshana Shenoy, Chitiphon Chuaicham, Keiko Sasaki, Sungkyun Park, Muthuchamy Nallal, Kang Hyun Park, Karthikeyan Sekar

    Chemical Communications    2023年

    DOI

  • All-alike hollow nanotubes of g-C3N4 converting photons into fuel by splitting water

    Mani Preeyanghaa, Chitiphon Chuaicham, Sulakshana Shenoy, Bernaurdshaw Neppolian, Keiko Sasaki, Karthikeyan Sekar

    Chemical Communications    2023年

    DOI

  • Unveiling the influence of Fe2O3 nanoparticles on CuxO–TiO2(B) nanofibers for dual Z-scheme electron transfer visible light photocatalysts: investigation on local atomic structures and electronic properties

    Mani Preeyanghaa, Chitiphon Chuaicham, Sulakshana Shenoy, Balakumar Vellaichamy, Wei Li, Kamaraj Manokaran, Elumalai Varathan, Bernaurdshaw Neppolian, Bunsho Ohtani, Keiko Sasaki, Karthikeyan Sekar

    Environmental Science: Nano    2023年

    DOI

  • Recent Clay-Based Photocatalysts for Wastewater Treatment

    Chitiphon Chuaicham, Jirawat Trakulmututa, Kaiqian Shu, Sulakshana Shenoy, Assadawoot Srikhaow, Li Zhang, Sathya Mohan, KARTHIKEYAN SEKAR, Keiko Sasaki

    Separations    2023年01月

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • Influence of aluminate and silicate on selenate immobilization using alkaline-earth metal oxides and ferrous salt

    Quanzhi Tian, Yingchu Bai, Yinhai Pan, Shuo Yao, Changshuai Chen, Haijun Zhang, Keiko Sasaki

    Science of The Total Environment   851   158126 - 158126  2022年12月  [査読有り]

    担当区分:責任著者

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Cu2O/Reduced Graphene Oxide Nanocomposites for Electrocatalytic Overall Water Splitting

    Muthuchamy Nallal, Kang Hyun Park, Sungkyun Park, Jaeyong Kim, Sulakshana Shenoy, Chitiphon Chuaicham, Keiko Sasaki, Karthikeyan Sekar

    ACS Applied Nano Materials    2022年11月

    DOI

    Scopus

    22
    被引用数
    (Scopus)
  • Occurrence of steel converter slag and its high value-added conversion for environmental restoration in China: A review

    Kaiqian Shu, Keiko Sasaki

    Journal of Cleaner Production   373   133876 - 133876  2022年11月  [査読有り]

    担当区分:責任著者

    DOI

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  • Effect of transformation temperature toward optical properties of derived CuO/ZnO composite from Cu–Zn hydroxide nitrate for photocatalytic ciprofloxacin degradation

    Jirawat Trakulmututa, Chitiphon Chuaicham, Sulakshana Shenoy, Assadawoot Srikhaow, Keiko Sasaki, Siwaporn Meejoo Smith

    Optical Materials   133   112941 - 112941  2022年11月

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    9
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  • Transition metal quantum dots for the electrocatalytic hydrogen evolution reaction: recent progresses and challenges

    Brahmari Honnappa, Sathya Mohan, Mariyappan Shanmugam, Ashil Augustin, Prince J. J. Sagayaraj, Chitiphon Chuaicham, Saravanan Rajendran, Tuan K. A. Hoang, Keiko Sasaki, Karthikeyan Sekar

    Energy Advances   1 ( 11 ) 738 - 760  2022年10月  [査読有り]

    担当区分:責任著者

     概要を見る

    Transition metal quantum dots composites for an electrocatalytic hydrogen evolution reaction.

    DOI

  • Conducting polymeric nanocomposites: A review in solar fuel applications

    Mariyappan Shanmugam, Ashil Augustin, Sathya Mohan, Brahmari Honnappa, Chitiphon Chuaicham, Saravanan Rajendran, Tuan K. A. Hoang, Keiko Sasaki, Karthikeyan Sekar

    FUEL   325  2022年10月  [査読有り]

     概要を見る

    Over the last few decades, research is being carried out in the field of photocatalysis to investigate for fuels production in sustainable manner. Due to an energy depletion and CO2 emission in the current situation urge us to produce alternative fuels. Water splitting and the reduction of carbon dioxide using various photocatalysts are being developed as promising sustainable methods to obtain eco-friendly energy sources. Conducting polymers (CP) stand out among the current pool of studied photocatalysts due to their high light absorption efficiency, good stability, tunable electronic characteristics, and cost effectiveness. Various CP, such as polyaniline, polythiophene, and polypyrrole have been integrated with different semiconducting nanomaterials to produce photocatalytic composites. Therefore, in this review, we focus on the synthesis of CP and their nanocomposites for application in CO2 photoreduction and water splitting into fuel production using different polymeric composites. Many composite photocatalysts show synergistic effects between the polymeric material and other counterparts in the composite. The improvement in the inactivity of the composite can be attributed to the band configurations of the composite. Improving the separation of excitons, widening the light absorption region, enhancing the substrate adsorption, and preventing photocorrosion conductive polymers can significantly increase the photocatalytic activity under visible light. The addition of conducting polymers with an inorganic materials dramatically change their band positions and may reduce the possiblilty of electron hole recombination. Here, we explain by what means conductive polymeric material can improve the efficiency of the composite in an organized manner, thereby providing a comprehensive reference to the field. Finally, the current challenges and future perspectives of polymeric catalysts have been discussed briefly.

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    23
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  • Efficient photocatalytic degradation of emerging ciprofloxacin under visible light irradiation using BiOBr/carbon quantum dot/saponite composite

    Chitiphon Chuaicham, Karthikeyan Sekar, Vellaichamy Balakumar, Junya Uchida, Takumi Katsurao, Hiroshi Sakabe, Bunsho Ohtani, Keiko Sasaki

    Environmental Research   212   113635 - 113635  2022年09月  [査読有り]

    担当区分:責任著者

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    26
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  • Determination of the roles of FeIII in the interface between titanium dioxide and montmorillonite in FeIII-doped montmorillonite/titanium dioxide composites as photocatalysts

    Li Zhang, Chitiphon Chuaicham, Vellaichamy Balakumar, Karthikeyan Sekar, Bunsho Ohtani, Keiko Sasaki

    Applied Clay Science   227   106577 - 106577  2022年09月  [査読有り]

    担当区分:責任著者

     概要を見る

    Fe/Mt./TiO2 with Fe-III cation doped on montmorillonite (Mt) and, Mt./Fe-TiO2 with Fe-III cation doped on TiO2 were synthesized at three temperatures. Compared with the influence from the position of Fe-III, the synthesis temperature had moderate interference on the TiO2 formation as was implied by X-ray fluorescence (XRF) and X-ray diffraction (XRD). Characterizations of diffuse reflectance UV-vis spectroscopy (DRS), photoluminescence spectroscopy (PL), photocurrent, and electrochemical impedance spectroscopy (EIS) indicated the more excellent photocatalytic property of Fe/Mt./TiO2 composite than Mt./Fe-TiO2 composite. The energy-resolved distribution of electron traps (ERDT) pattern revealed a distinguished phase composing from the surface to the bulk for both Fe/Mt./TiO2 and Mt./Fe-TiO2 and demonstrated almost the same photocatalytic property of the TiO2 particle surface on both Fe/Mt./TiO2 and Mt./Fe-TiO2. The photocatalytic activities test for phenol decomposition on Fe/Mt./TiO2 was better than Mt./Fe-TiO2 which is consistent with the DRS, PL, photocurrent, and EIS results. A heterojunction between the Mt. and TiO2 in Fe/Mt./TiO2 was proposed to explain the inconsistency of the photocatalytic property and photocatalytic performance for the two composites and the consistency of the photocatalytic property for the surface of TiO2 particles on the composites. To increase the photocatalytic activity of Fe/Mt./TiO2, the electron at the Fermi level on Fe-III-doped Mt. may be coupled with the hole on the valance band of TiO2, resulting in effective separation of electron and hole and reduction and/or avoidance of recombination.

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    4
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  • Effect of ionic Fe(III) doping on montmorillonite for photocatalytic reduction of Cr(VI) in wastewater

    Li Zhang, Chitiphon Chuaicham, Vellaichamy Balakumar, Keiko Sasaki

    Journal of Photochemistry and Photobiology A: Chemistry   429   113909 - 113909  2022年08月  [査読有り]

    担当区分:責任著者

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    6
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  • Effect of sodium metabisulfite and slaked lime on the floatability and surface properties of chalcopyrite

    Gde Pandhe Wisnu Suyantara, Yuki Semoto, Hajime Miki, Tsuyoshi Hirajima, Keiko Sasaki, Daishi Ochi, Yuji Aoki, Daniyarov Berdakh, Kumika Ura

    Powder Technology   408   117750 - 117750  2022年08月  [査読有り]

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    5
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  • Application of Geopolymer in Stabilization/Solidification of Hazardous Pollutants: A Review

    Quanzhi Tian, Yingchu Bai, Yinhai Pan, Changshuai Chen, Shuo Yao, Keiko Sasaki, Haijun Zhang

    Molecules    2022年07月

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    35
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  • Recent development on core-shell photo(electro)catalysts for elimination of organic compounds from pharmaceutical wastewater

    Surendar Balu, Chitiphon Chuaicham, Vellaichamy Balakumar, Saravanan Rajendran, Keiko Sasaki, Karthikeyan Sekar, Arthanareeswari Maruthapillai

    CHEMOSPHERE   298   134311 - 134311  2022年07月  [査読有り]

    担当区分:責任著者

     概要を見る

    Pharmaceutical organics are a vital milestone in contemporary human research since they treat various diseases and improve the quality of human life. However, these organic compounds are considered one of the major environmental hazards after the conception, along with the massive rise in antimicrobial resistance (AMR) in an ecosystem. There are various biological and catalytic technologies existed to eliminate these organics in aqueous system with their limitation. Advanced Oxidation processes (AOPs) are used to decompose these pharmaceutical organic compounds in the wastewater by generating reactive species with high oxidation potential. This review focused various photocatalysts, and photocatalytic oxidation processes, especially core-shell materials for photo (electro)catalytic application in pharmaceutical wastewater decomposition. Moreover, we discussed in details about the design and recent developments of core shell catalysts and comparison for photocatalytic, electrocatalytic and photo electrocatalytic applications in pharmaceutical wastewater treatment. In addition, the mixture of inorganic and organic core-shell materials, and metal-organic framework-based core-shell catalysts discussed in detail for antibiotic degradation.

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    29
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  • Enhanced photocatalytic reduction of hexavalent chromium ions over Zn-bearing in CuZn hydroxy double salts: Insight into the structural investigation using extended X-ray absorption fine structure

    Chitiphon Chuaicham, Karthikeyan Sekar, Vellaichamy Balakumar, Li Zhang, Jirawat Trakulmututa, Pinit Kidkhunthod, Siwaporn Meejoo Smith, Keiko Sasaki

    Colloids and Surfaces A: Physicochemical and Engineering Aspects   645   128893 - 128893  2022年07月  [査読有り]

    担当区分:責任著者

     概要を見る

    CuZn hydroxy double salts (CuZn-HDS) are often used as adsorbent and Fenton-like catalysts. In this work, we report the photocatalytic activity of CuZn-HDS for Cr(VI) reduction. In detail, CuZn-HDS with different Cu/Zn ratios were prepared as photocatalysts through the metal oxide-assisted hydrothermal method. The CuZn-HDS samples were characterized and applied for photocatalytic reduction of Cr(VI), which is a toxic inorganic pollutant in the wastewater. The CuZn-HDS which has the Cu/Zn ratio of about 4 (CuZn-HDS-4) showed the heist photocatalytic Cr(VI) reduction activity more than other samples, especially for copper hydroxy salts (Cu-HS) which have no Zn in the structure. Thus, the Zn-bearing in CuZn hydroxy double can improve the photocatalytic activity for Cr(VI) reduction compared with Cu-HS. The increase in the Cr(VI) reduction activity of the optimized CuZn-HDS-4 was attributed to the excellent separation and transportation of photogenerated electron-holes pairs, as proven by the photoluminescence, photocurrent density, and electrochemical impedance spectroscopy results. Moreover, the atomic structure of the synthesized CuZn-HDS was elucidated by an extended X-ray absorption fine structure technique, which is the first time to report the CuZn-HDS structure. Based on the optical properties, and activity test, a photocatalytic reduction of Cr(VI) over a CuZn-HDS was proposed. Thus, the CuZnHDS can be employed as a potential photocatalyst for the detoxification of Cr(VI) in wastewater.

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    5
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  • Laccase-mediator system for enzymatic degradation of carbonaceous matter in the sequential pretreatment of double refractory gold ore from Syama mine, Mali

    Ryotaro Sakai, Diego M. Mendoza, Kojo T. Konadu, Cindy, Yuji Aoki, Tsuyoshi Hirajima, Hirofumi Ichinose, Keiko Sasaki

    Hydrometallurgy   212   105894 - 105894  2022年06月

    担当区分:責任著者

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    8
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  • Effect of amino acids on the stability of anionic pollutants in fly ash blended cement

    Mengmeng Wang, Keiko Sasaki

    Journal of Environmental Chemical Engineering   10 ( 3 ) 107926 - 107926  2022年06月  [査読有り]

    担当区分:責任著者

    DOI

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    1
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  • Recent development of organic-inorganic hybrid photocatalysts for biomass conversion into hydrogen production

    Ashil Augustin, Chitiphon Chuaicham, Mariyappan Shanmugam, Balakumar Vellaichamy, Saravanan Rajendran, Tuan K. A. Hoang, Keiko Sasaki, Karthikeyan Sekar

    NANOSCALE ADVANCES   4 ( 12 ) 2561 - 2582  2022年06月

     概要を見る

    Over the last few years, photocatalysis using solar radiation has been explored extensively to investigate the possibilities of producing fuels. The production and systematic usage of solar fuels can reduce the use of fossil-based fuels, which are currently the primary source for the energy. It is time for us to exploit renewable sources for our energy needs to progress towards a low-carbon society. This can be achieved by utilizing green hydrogen as the future energy source. Solar light-assisted hydrogen evolution through photocatalytic water splitting is one of the most advanced approaches, but it is a non-spontaneous chemical process and restricted by a kinetically demanding oxidation evolution reaction. Sunlight is one of the essential sources for the photoreforming (PR) of biomass waste into solar fuels, or/and lucrative fine chemicals. Hydrogen production through photoreforming of biomass can be considered energy neutral as it requires only low energy to overcome the activation barrier and an alternate method for the water splitting reaction. Towards the perspective of sustainability and zero emission norms, hydrogen production from biomass-derived feedstocks is an affordable and efficient process. Widely used photocatalyst materials, such as metal oxides, sulphides and polymeric semiconductors, still possess challenges in terms of their performance and stability. Recently, a new class of materials has emerged as organic-inorganic hybrid (OIH) photocatalysts, which have the benefits of both components, with peculiar properties and outstanding energy conversion capability. This work examines the most recent progress in the photoreforming of biomass and its derivatives using OIHs as excellent catalysts for hydrogen evolution. The fundamental aspects of the PR mechanism and different methods of hydrogen production from biomass are discussed. Additionally, an interaction between both composite materials at the atomic level has been discussed in detail in the recent literature. Finally, the opportunities and future perspective for the synthesis and development of OIH catalysts are discussed briefly with regards to biomass photo-reforming.

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    20
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  • Fabrication of graphitic carbon nitride/ZnTi-mixed metal oxide heterostructure: Robust photocatalytic decomposition of ciprofloxacin

    Chitiphon Chuaicham, Karthikeyan Sekar, Vellaichamy Balakumar, Yanisa Mittraphab, Kuniyoshi Shimizu, Bunsho Ohtani, Keiko Sasaki

    Journal of Alloys and Compounds   906   164294 - 164294  2022年06月

    担当区分:責任著者

     概要を見る

    Photocatalytic treatment is a remarkable process that is popular for the degradation of several organic contaminants in wastewater. In this work, a series of graphitic carbon nitride/ZnTi-mixed metal oxide (CN/ ZnTi-MMO) composites were prepared as photocatalysts through simple calcination. The CN-MMO samples were characterized and applied for photocatalytic degradation of ciprofloxacin (CIP), which is an antibiotic model pollutant. The optimized CN/ZnTi-MMO composite showed complete degradation of CIP within 20 min, leading to a rate constant that is approximately 6 times that of pristine CN and 7 times that of ZnTiMMO. The increase in the degradation rate of the optimized CN/ZnTi-MMO composite was attributed to the excellent separation and transportation of photogenerated electron-holes pairs, as proven by the photoluminescence, photocurrent density, and electrochemical impedance spectroscopy results. Moreover, the energy-resolved distribution of the electron trap (ERDT) pattern of the composite sample suggests the formation of an interfacial electron trap state due to interfacial contraction in the composite, resulting in the excited electrons being trapped and avoiding charge recombination. Based on the optical properties, ERDT results, and activity test, a photocatalytic degradation mechanism of CIP over a CN/ZnTi-MMO composite was proposed. Additionally, the degraded solution showed less bio-toxicity than the original CIP solution. Thus, the CN/ZnTi-MMO composite can be employed as a potential visible-light-driven photo catalyst for the detoxification of pharmaceutical wastewater.(c) 2022 Elsevier B.V. All rights reserved.

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    23
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  • A Critical Study of Cu2O: Synthesis and Its Application in CO2 Reduction by Photochemical and Electrochemical Approaches

    Sathya Mohan, Brahmari Honnappa, Ashil Augustin, Mariyappan Shanmugam, Chitiphon Chuaicham, Keiko Sasaki, R. Boopathy, KARTHIKEYAN SEKAR

    Catalysts   12 ( 4 ) 445 - 445  2022年04月

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    12
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  • Fabrication of visible-light-active ZnCr mixed metal oxide/fly ash for photocatalytic activity toward pharmaceutical waste ciprofloxacin

    Chitiphon Chuaicham, Takumi Inoue, Vellaichamy Balakumar, Quanzhi Tian, Keiko Sasaki

    Journal of Industrial and Engineering Chemistry   108   263 - 273  2022年04月  [査読有り]

    担当区分:責任著者

     概要を見る

    Visible active photocatalysts have attracted interest as a potentially efficient and sustainable approach for pollutant degradation treatment. In this work, ZnCr mixed metal oxide/fly ash (ZnCr-MMO/FA) compos-ites were prepared using fly ash (FA) from China coal mining power plants to improve photocatalytic per-formance. The formation of the ZnCr-MMO/FA composites was proved by XRD results which showed the two-phases combination of FA and MMO. Also, the presence of FA in the ZnCr-MMO/FA composite pro-vided a good arrangement of small particles of ZnCr-MMO on the surface of FA and higher light absorp-tion ability with a lower energy bandgap compared with the pure ZnCr-MMO. The photocatalytic performance of the prepared ZnCr-MMO and ZnCr-MMO/FA composites in different FA contents was evaluated by degradation of ciprofloxacin (CIP), which is an antibiotic and often found in pharmaceutical wastes, under visible light irradiation. Clearly, the ZnCr-MMO/FA composites showed higher photocat-alytic decomposition of CIP than pristine ZnCr-MMO, and the highest degradation performance for CIP was obtained from the ZnCr-MMO/FA sample with 0.5 mg FA, which has a reaction rate constant approx-imately four times greater than that of pure ZnCr-MMO. The improved CIP degradation activity of the ZnCr-MMO/FA composite might not only be due to the good arrangement of ZnCr-MMO particles on the FA surface but also high separation and less recombination of photogenerated electrons-holes pairs, proven by the photoluminescence spectra, photocurrent density, and electrochemical impedance spec-troscopy results. The lower recombination of the charge carriers of the ZnCr-MMO/FA composite might be caused by the heterojunction between the ZnCr-MMO as a main photocatalyst and FA. Thus, the pro-posed ZnCr-MMO/FA composite can be used as an effective photocatalyst for wastewater treatment, including the decomposition of organic pollutants, such as discarded pharmaceuticals.(c) 2022 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

    DOI

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    11
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  • Synthesis, characterization, and application of MOF@clay composite as a visible light-driven photocatalyst for Rhodamine B degradation

    Radheshyam Rama Pawar, Chitiphon Chuaicham, Karthikeyan Sekar, Saravanan Rajendran, Keiko Sasaki

    CHEMOSPHERE   291  2022年03月

     概要を見る

    Metal Organic Frameworks (MOFs) with natural clay materials is a relatively new research avenue that appears to reduce high production costs and address the instability issues of pure MOFs. A novel MOF and natural clay composites of MOF@Sp_n (n = 1-4) were fabricated by the in situ precipitation of stable MOF, Zr6O4(OH)(4) (ABDC)(6) (where ABDC = 2-aminobenzene-1,4-dicarboxylic acid), over natural sepiolite (Sp) clay and used as a photocatalysts for elimination of organic dyes in aqueous media. The formation of MOF@Sp_n due to its strong electrostatic interactions between the positively charged MOF and the negatively charged sepiolite. Optimizing the Sp content in the composite strongly influenced the dispersibility, crystallinity of MOFs, resulting in progressively functional hybrid materials with an excellent optoelectronic properties. The composites lessened the shortcomings of the individual components and made them suitable as a visible light-active, highly efficient, standalone photocatalyst material that can degrade RhB.

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    22
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  • Visible light-driven ZnCr double layer oxide photocatalyst composites with fly ashes for the degradation of ciprofloxacin

    Chitiphon Chuaicham, Takumi Inoue, Vellaichamy Balakumar, Quanzhi Tian, Bunsho Ohtani, Keiko Sasaki

    JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING   10 ( 1 )  2022年02月

     概要を見る

    Zn-Cr layered double oxide/fly ash (ZnCrLDO/FA) composites were synthesized using three different fly ashes (YEM, DAT, PAN) as photocatalysts for the degradation of ciprofloxacin through in situ coprecipitation followed by calcination. Ciprofloxacin (10 mg/L) was completely decomposed more than 98% within 120 min by ZnCrLDO/YEM composites in aqueous conditions, which indicates that the heterojunction between ZnCrLDO and YEM may help electrons move easily to enhance the separation of the electron-hole pairs. Based on the XPS results for the three fly ash samples, the largest Fe and Ti content was detected on the YEM, which suggests that TiO2, Fe2O3 on the surface of fly ash are responsible for the heterojunction. Furthermore, the ERDT pattern of ZnCrLDO/YEM confirmed the formation of new electronic levels that may avoid the recombination of electronhole pairs, which leads to the enhancement of photocatalytic performance. These results show that fly ash is essential as supporting material to avoid the agglomeration of ZnCrLDO particles and as an electron carrier for enhancing the mobility of photogenerated electrons in photocatalyst composites.

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    24
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  • Designing novel magnesium oxysulfate cement for stabilization/solidification of municipal solid waste incineration fly ash

    Lei Wang, Yuying Zhang, Liang Chen, Binglin Guo, Yongshan Tan, Keiko Sasaki, Daniel C.W. Tsang

    Journal of Hazardous Materials   423   127025 - 127025  2022年02月  [査読有り]

    担当区分:責任著者

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    111
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  • Fabrication of Hydrotalcite-like Copper Hydroxyl Salts as a Photocatalyst and Adsorbent for Hexavalent Chromium Removal

    Chitiphon Chuaicham, Karthikeyan Sekar, Vellaichamy Balakumar, Li Zhang, Jirawat Trakulmututa, Siwaporn Meejoo Smith, Keiko Sasaki

    Minerals   12 ( 2 ) 182 - 182  2022年01月  [査読有り]

    担当区分:責任著者

     概要を見る

    Cu-HyS-urea and Cu-HyS-NaOH, which are hydrotalcite-like copper hydroxyl salts, were prepared by two different methods, urea hydrolysis and precipitation, respectively. Both synthesis methods provided the successful formation of a copper hydroxyl salt, Cu2(OH)3NO3. From XRD and UV-DRS results, the product from the urea hydrolysis methods (Cu-HyS-urea) displayed higher crystallinity, small bandgap energy (Eg), and high light absorption ability because of some intercalated carbonate anions. For the Cr(VI) removal test, the Cu-HyS-NaOH showed superior adsorption of Cr(VI) than Cu-HyS-urea due to a higher specific surface area, confirmed by BET analysis. However, the Cu-HyS-urea presented higher photocatalytic Cr(VI) reduction under light irradiation than Cu-HyS-NaOH, owing to narrow Eg, less recombination, and a high transfer of the photogenerated charge carriers, proven by the results from photoluminescence, photocurrent density, and electrochemical impedance spectroscopy. Thus, this work provides a new function of the hydrotalcite-like copper hydroxyl salts (Cu-HyS-urea and Cu-HyS-NaOH) that can be utilized not only for adsorption of Cr(VI) but also as photocatalysts for Cr(VI) reduction under light irradiation.

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    6
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  • Bioinspired Nanomaterials for Photocatalytic Degradation of Toxic Chemicals

    Vellaichamy Balakumar, Ramalingam Manivannan, Keiko Sasaki

    Materials Research Foundations   121   83 - 116  2022年  [査読有り]

    担当区分:責任著者

  • Stabilization/solidification of radioactive waste in geochemical aspects

    Binglin Guo, Keiko Sasaki

    Low Carbon Stabilization and Solidification of Hazardous Wastes     469 - 482  2022年  [査読有り]

    DOI

  • Upcycling hazardous metals and PET waste-derived metal–organic frameworks: a review on recent progresses and prospects

    Mariyappan Shanmugam, Chitiphon Chuaicham, Ashil Augustin, Keiko Sasaki, Prince J. J. Sagayaraj, Karthikeyan Sekar

    New Journal of Chemistry   46 ( 33 ) 15776 - 15794  2022年  [査読有り]

    担当区分:責任著者

     概要を見る

    An intense increase in non-biodegradable plastics and waste metals is an immediate threat to the world and needs to be addressed urgently.

    DOI

  • Fabrication of Adsorbed Fe(III) and Structurally Doped Fe(III) in Montmorillonite/TiO2 Composite for Photocatalytic Degradation of Phenol

    Li Zhang, Chitiphon Chuaicham, Dr. Balakumar Vellaichamy, Bunsho Ohtani, Keiko Sasaki

    Minerals    2021年12月

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    9
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  • Effect of Sodium Metabisulfite on Selective Flotation of Chalcopyrite and Molybdenite

    Yuki Semoto, Gde Pandhe Wisnu Suyantara, Hajime Miki, Keiko Sasaki, Tsuyoshi Hirajima, Yoshiyuki Tanaka, Yuji Aoki, Kumika Ura

    Minerals   11 ( 12 ) 1377 - 1377  2021年12月  [査読有り]

     概要を見る

    Sodium metabisulfite (MBS) was used in this study for selective flotation of chalcopyrite and molybdenite. Microflotation tests of single and mixed minerals were performed to assess the floatability of chalcopyrite and molybdenite. The results of microflotation of single minerals showed that MBS treatment significantly depressed the floatability of chalcopyrite and slightly reduced the floatability of molybdenite. The results of microflotation of mixed minerals demonstrated that the MBS treatment could be used as a selective chalcopyrite depressant in the selective flotation of chalcopyrite and molybdenite. Furthermore, the addition of diesel oil or kerosene could significantly improve the separation efficiency of selective flotation of chalcopyrite and molybdenite using MBS treatment. A mechanism based on X-ray photoelectron spectroscopy analysis results is proposed in this study to explain the selective depressing effect of MBS on the flotation of chalcopyrite and molybdenite.

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  • Single-step synthesis of oxygen-doped hollow porous graphitic carbon nitride for photocatalytic ciprofloxacin decomposition

    Chitiphon Chuaicham, Karthikeyan Sekar, Yihuang Xiong, Vellaichamy Balakumar, Yanisa Mittraphab, Kuniyoshi Shimizu, Bunsho Ohtani, Ismaila Dabo, Keiko Sasaki

    CHEMICAL ENGINEERING JOURNAL   425  2021年12月

     概要を見る

    Pollutants degradation via visible-light driven photocatalysts have attracted interest as a potentially efficient and sustainable approach for wastewater treatment. In the present study, a series of oxygen-doped hollow porous surface graphitic carbon nitride (OCN) has been prepared by one-pot thermal polycondensation of melamine with different amounts of polyoxyethylene stearyl ether as the oxygen source and template. The prepared OCN samples were utilized for the photocatalytic ciprofloxacin (CIP) degradation, which is a pharmaceutical waste, under visible light irradiation. The highest degradation performance for CIP was obtained from the OCN sample with 1 mg polyoxyethylene stearyl, which was three times greater than that of pristine C3N4. The superior degradation performance of the OCN samples were observed due to the improved light absorption, less recombination rate of photogenerated electron and hole, and enhanced electron transportation, which was proven through the PL, photocurrent density, and EIS results. Thus, the proposed one-pot synthesis of OCN provides an effective method in producing potential photocatalysts for the removal of organic pollutants, such as discarded pharmaceuticals, in wastewater.

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    45
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  • 2
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  • Environmental impact of amino acids on selenate-bearing hydrocalumite: Experimental and DFT studies

    Mengmeng Wang, Hirofumi Akamatsu, Ismaila Dabo, Keiko Sasaki

    Environmental Pollution   288   117687 - 117687  2021年11月  [査読有り]

    担当区分:責任著者

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    5
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  • Effect of Na2SO3 on the floatability of chalcopyrite and enargite

    Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Hajime Miki, Keiko Sasaki, Shigeto Kuroiwa, Yuji Aoki

    Minerals Engineering   173   107222  2021年09月  [査読有り]

  • Degradation of powder activated carbon by laccase mediated system: model experiment for improvement of gold recovery from carbonaceous gold ore

    Diego Mendoza, Kojo Konadu, Hirofumi Ichinose, Keiko Sasaki

    Journal of Environmental Chemical Engineering   9   106375  2021年08月  [査読有り]

    担当区分:最終著者, 責任著者

  • Influence of Amino Acids on the Mobility of Iodide in Hydrocalumite

    Mengmeng Wang, Hirofumi Akamatsu, Keiko Sasaki

    Minerals   11 ( 8 ) 836 - 836  2021年08月  [査読有り]

    担当区分:最終著者, 責任著者

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    5
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    (Scopus)
  • Fabrication and characterization of CQDs decorated hollow porous graphitic carbon nitride through polyaniline for photocatalysis

    Vellaichamy Balakumar, Ramalingam Manivannan, Chitiphon Chuaicham, Sekar Karthikeyan, Keiko Sasaki

    Chemical Engineering Journal   426   131739  2021年07月  [査読有り]

    担当区分:最終著者, 責任著者

     概要を見る

    Metal-free photocatalysts are widely used to decontaminate aqueous solutions by eliminating toxic and nonbiodegradable compounds. It is desirable to develop a photocatalyst with high charge separation and migration efficiency. The addition of carbon quantum dots (CQDs) to graphitic carbon nitride with polyaniline (PANI) can improve its light absorption abilities and reduce the recombination of holes and electrons. In this study, a novel CQDs decorated on PANI with hollow porous graphitic carbon nitride (CN) was fabricated via an in situ polymerization followed by an ultra-sonication. The optimal CQDs-loaded CN-PANI nanocomposite exhibited the high visible light absorption with a high specific surface area. Furthermore, better photocatalytic degradation of ciprofloxacin (CIP) was achieved under the visible light. The improved photocatalytic activity of CN-PANICQDs (5.0%) can be attributed to its higher charge separation, and destruction of recombination rate through the heterojunction of excited electrons among CN, PANI, and CQDs. This effect was further confirmed by high photocurrent intensity, low photoluminescence emission, and electrical resistance. In addition, different parameters including catalyst weight, initial CIP concentration, and interfering effect of anions during CIP removal were investigated. The main active species in the degradation of CIP were identified to h+, center dot OH, and center dot O-2(-) through the scavenger test. The high reusability and stability of the photocatalyst composite were also verified. The degradation intermediates and reaction pathways were identified. Furthermore, the effectiveness of the photocatalyst was evaluated using different toxic pollutants including imidacloprid, tetracycline, phenol, and rhodamine B under similar conditions. The CQDs-decorated CN-PANI was proved as a promising material for efficient photodegradation of toxic pollutants in water.

    DOI

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    48
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  • Elution characteristics of undesirable anionic species from fly ash blended cement in different aqueous solutions

    Keiko Sasaki, Shingo Nakama, Quanzhi Tian, Binglin Guo, Mengmeng Wang, Ryoichi Takagi, Tomohiko Takahashi

    Journal of Environmental Chemical Engineering   9 ( 3 ) 105171 - 105171  2021年06月  [査読有り]

    担当区分:筆頭著者, 責任著者

    DOI

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    3
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  • Synergistic metal-free porous CN-PPy-MMt nanocomposite for efficient photocatalytic metronidazole mineralization performance, mechanism and pathways

    Vellaichamy Balakumar, Sekar Karthikeyan, Chitiphon Chuaicham, Ramalingam Manivannan, Keiko Sasaki

    Environmental Science: Nano   8 ( 8 ) 2261 - 2276  2021年05月  [査読有り]

    担当区分:最終著者, 責任著者

     概要を見る

    Carbon nitride based photocatalysts are widely used to decontaminate aqueous solutions by eliminating toxic and non-biodegradable compounds. It is desirable to develop a photocatalyst with high charge separation and migration efficiency. In this study, synergistic ternary porous carbon nitride-polypyrrole-montmorillonite (CN-PPy-MMt) was successfully synthesized via an in situ oxidative polymerization method. The photocatalytic performance towards mineralization of metronidazole (MZ) under visible light was studied, where the CN-PPy-MMt (10%) nanocomposite exhibited the best performance compared to CN-PPy-MMt (5%, 15%, 20%), CN-PPy, pure CN and other nanocomposites reported. This superior photocatalytic mineralization performance was attributed to synergistic inter-constituent interactions within the CN-PPy-MMt nanocomposite, which effectively enhanced the light absorption capacity and charge transfer, and reduced the recombination of electron-hole pairs. The results were confirmed by UV-DRS, photocurrent, impedance, and photoluminescence measurements. The effect of interfering anions was examined and the results indicated that the MZ mineralization efficiency was significantly inhibited by the addition of HCO3- and PO43-. The reusability and stability of the photocatalyst were excellent even after five repeated photocatalytic reactions. Analysis of the radical scavenger properties indicated that superoxide radicals (O-2(-)) and holes (h(+)) played a major role in the mineralization of MZ. The intermediate products were confirmed using liquid chromatography-mass spectrometry, which provided an insight into the MZ mineralization mechanism. This work suggested that the design of a ternary nanocomposite based on CN with conducting polymers could be an effective strategy to improve the photocatalytic mineralization of antibiotics and energy related applications.

    DOI

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    22
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  • Surfactant- and template-free hydrothermal assembly of Cu2O visible light photocatalysts for trimethoprim degradation

    Karthikeyan Sekar, Chitiphon Chuaicham, Umamahesh Balijapalli, Wei Li, Karen Wilson, Adam F. Lee, Keiko Sasaki

    Applied Catalysis B: Environmental   284   119741 - 119741  2021年05月  [査読有り]

    担当区分:責任著者

     概要を見る

    A surfactant-free, low temperature hydrothermal synthesis of Cu2O nanostructures is demonstrated for application to the photocatalytic degradation of trimethoprim (TMP), an environmental xenobiotic. Photophysical properties of different size and shape Cu2O nanostructures were determined by bulk and surface microscopic and spectroscopic analyses. Visible light photoactivity for the oxidative degradation of TMP is sensitive to the rate of photoexcited charge carrier bulk recombination, and therefore the size of Cu2O crystallites. Optimum photodegradation activity was observed for a hierarchical Cu2O nanostructure, comprising 11 nm crystallites nucleated as 50-80 nm particles, themselves coalesced into 400 nm compact agglomerates. The specific activity of 1.12 mu mol.g(-1). min(-1) for a 0.1 mM TMP aqueous solution is comparable to previous reports that required higher energy and/intensity UV irradiation. The stepwise hydroxylation and oxidative cleavage of TMP to form monocylic fragments is driven by hydroxyl radicals photogenerated over the hierarchical Cu2O nanostructure, which exhibits excellent catalytic stability for >25 h.

    DOI

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    58
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  • A simple tactic synthesis of hollow porous graphitic carbon nitride with significantly enhanced photocatalytic performance

    Vellaichamy Balakumar, Ramalingam Manivannan, Chitiphon Chuaicham, Sekar Karthikeyan, Keiko Sasaki

    Chemical Communications   57 ( 55 ) 6772 - 6775  2021年04月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

  • Cubic Cu2O nanoparticles decorated on TiO2 nanofiber heterostructure as an excellent synergistic photocatalyst for H2 production and sulfamethoxazole degradation

    Karthikeyan Sekar, Chitiphon Chuaicham, Balakumar Vellaichamy, Wei Li, Wei Zhuang, Xiaohua Lu, Bunsho Ohtani, Keiko Sasaki

    Applied Catalysis B: Environmental   294   120221 - 120221  2021年04月  [査読有り]

    担当区分:責任著者

     概要を見る

    We report a simple strategy for providing a homogenous TiO2 nanofibre host environment to stabilize Cu2O nanoparticles with an average size of similar to 60 nm and high dispersibility. We found that the small fraction of Cu2O nanoparticles in direct contact/partially submerged with TiO2 nanofibre arrays (diameter similar to 300 nm and length similar to 650 nm) showed excellent synergistic photocatalytic performance for H-2 production rate of 48 mu mol g (-1) h(-1) with an apparent quantum efficiency of 3.6 %. The H-2 production rate was much higher (factor of similar to 6.5 times) compared with unmodified TiO2-NF. In addition, the synergistic Cu2O/TiO2-NF photocatalyst showed significant oxidative-degradation of sulfamethoxazole (7 x 10(-2) mmol g (-1) min(-1)) and was highly stable during five cycles. The small fraction of Cu2O nanoparticles are well dispersed and form heterojunction interfaces to promote charge transfer and provide active sites. This argument is verified by morphology characterisation, band alignment, energy-resolved distribution of electron traps, electrochemical transient photocurrent, and electrochemical impedance (EIS). In addition, a detailed discussion is provided regarding the surface and bulk elemental composition determined by X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), and X-ray absorption near edge structure (XANES).

    DOI

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    89
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  • Effect of Si/Al molar ratio on the immobilization of selenium and arsenic oxyanions in geopolymer

    Quanzhi Tian, Changshuai Chen, MengMeng Wang, Binglin Guo, Haijun Zhang, Keiko Sasaki

    Environmental Pollution   274   116509 - 116509  2021年04月  [査読有り]

    担当区分:責任著者

     概要を見る

    The effect of Si/Al molar ratio of geopolymer on the immobilization of Se and As oxyanions was studied through leaching test and solid characterizations including XRD, FTIR, TG, NMR, XAFS, and N adsorption-desorption isotherm. As a whole, the leaching percentages of Se and As oxyanions increased with the increase of the Si/Al molar ratio of geopolymer. Linear combination fitting confirmed that most of selenite, selenate and arsenate ions existed in geopolymers through electrostatic interaction. Thus, Al tetrahedrons in geopolymer structure control the charge stability for these oxyanions to a large extent. Differently, as for arsenate ions, they were recrystallized into an arsenate compound (Na (OH) (H O) )(AsO ) in geopolymers. The additive of these pollutants has an adverse effect on the compactness of geopolymer, then influencing the leaching performance in turn. However, the changes in leaching results did not follow the variation trend of specific surface areas and pore volumes of geopolymers with different Si/Al ratios. The number and distribution of Al tetrahedron and compactness of geopolymer have a synergistic effect on the immobilization of these oxyanions. Besides, the compressive strengths of geopolymer samples are always higher than 20 MPa, which meets the requirement of safe disposal of hazardous waste. 2 3.25 0.25 2 12 4

    DOI PubMed

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    24
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  • A promising Zn-Ti layered double hydroxide/Fe-bearing montmorillonite composite as an efficient photocatalyst for Cr(VI) reduction: Insight into the role of Fe impurity in montmorillonite

    Chitiphon Chuaicham, Yihuang Xiong, Karthikeyan Sekar, Weinan Chen, Li Zhang, Bunsho Ohtani, Ismaila Dabo, Keiko Sasaki

    Applied Surface Science   546   148835 - 148835  2021年04月  [査読有り]

    担当区分:責任著者

     概要を見る

    Zn-Ti layered double hydroxide/montmorillonite (ZTL/MT) and Fe-doped ZTL/MT (ZTL/Fe@MT20%) were prepared as photocatalyst for Cr(VI) reduction. The ZTL/Fe@MT20% exhibited the highest photocatalytic activity, suggesting that a combination of ZTL and Fe-bearing MT could enhance photocatalytic activity by suppressing the recombination of photogenerated electron-hole pairs. On the basis of electronic-structure calculations, a photocatalytic mechanism for Cr(VI) reduction and the effect of Fe3+ on the structure of MT in ZTL/MT composites is proposed by density functional theory approach, whereby Fe impurities in MT generate a new mid-gap state that induce a Z-scheme heterojunction with ZTL, leading to reduced recombination of the photogenerated charge carriers in ZTL. These results establish that MT can not only act as a support material but also play an important role for photocatalytic reaction when Fe impurities are present in its structure.

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    34
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  • Structural characterizations of fly ash-based geopolymer after adsorption of various metal ions

    Quanzhi Tian, Keiko Sasaki

    Environmental Technology   42 ( 6 ) 941 - 951  2021年03月  [査読有り]

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    13
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  • Hierarchical bismuth vanadate/reduced graphene oxide composite photocatalyst for hydrogen evolution and bisphenol A degradation

    Karthikeyan Sekar, Ahmed Kassam, Yang Bai, Ben Coulson, Wei Li, Richard E. Douthwaite, Keiko Sasaki, Adam F. Lee

    Applied Materials Today   22   100963 - 100963  2021年03月  [査読有り]

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    43
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  • Carbonaceous matter degradation by fungal enzyme treatment to improve Ag recovery from an Au-Ag-bearing concentrate

    Diego M. Mendoza, Kojo T. Konadu, Yuji Aoki, Misato Kameya, Keiko Sasaki

    Minerals Engineering   163   106768 - 106768  2021年03月  [査読有り]

    担当区分:責任著者

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    8
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  • Synthesis and characterization of defective UiO-66 for efficient co-immobilization of arsenate and fluoride from single/binary solution

    Subbaiah Muthu Prabhu, Chitiphon Chuaicham, Chang Min Park, G. Paruthimal Kalaignan, Keiko Sasaki

    Environmental Pollution   278   116841 - 116850  2021年02月  [査読有り]

    担当区分:責任著者

  • Environmental impact of amino acids on the release of selenate immobilized in hydrotalcite: Integrated interpretation with experimental and DFT studies

    Mengmeng Wang, Hirofumi Akamatsu, Ismaila Dabo, Keiko Sasaki

    Chemosphere   274   129927  2021年02月  [査読有り]

    担当区分:責任著者

  • Effects of Mg compounds in hydroxylated calcined dolomite as an effective and sustainable substitute of lime to precipitate as ettringite for treatment of selenite/selenate in aqueous solution

    Binglin Guo, Quanzhi Tian, Tsubasa Oji, Lei Wang, Keiko Sasaki

    Colloids and Surfaces A: Physicochemical and Engineering Aspects   610   125782 - 125782  2021年02月  [査読有り]

    担当区分:責任著者

     概要を見る

    The elevated level of selenium (Se) in the aqueous system presents long-term ecological risks. Hydroxylated calcined dolomites (HCDs) are considered as potentially sustainable lime sources due to their lower production temperatures and resourceful than lime. In this study, HCDs were developed for the removal of Se contaminated water. The HCDs exhibited a better performance to co-precipitate with Se oxyanions than pure Ca(OH) . Considering that HCDs consisted of Ca(OH) with MgO and Mg(OH) , the function of Mg compounds was also elaborated by various characterization techniques. Mg compounds were proved to enhance the precipitation process and Se removal. STEM-EDX observation revealed that SeO was incorporated into the ettringite structure with Mg compounds, whereas SeO exhibited a affinity to Mg compounds. Extended X-ray absorption fine structure (EXAFS) results for the MgO/Mg(OH) after the reaction proved that both SeO interacted with Mg(OH) and MgO via inner-sphere complexes whereas SeO formed outer-sphere complexes with these Mg compounds. Besides, Mg compounds also influenced the surface charge of solid residues and thus enhanced SeO removal. This study provides a fundamental understanding of the roles of Mg compounds in the removal of Se oxyanions during environmental remediation. Besides, the HCDs were proved to be sustainable Ca sources for waste/wastewater remediation. 2 2 2 3 4 2 3 2 4 3 2– 2– 2– 2– 2–

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    5
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  • Synthesis and characterization of imidazole-bearing polymer-modified montmorillonite for adsorption of perchlorate

    Li Zhang, Srinivasarao Kancharla, Keiko Sasaki

    Applied Clay Science   199   105859 - 105859  2020年12月  [査読有り]

    担当区分:責任著者

    DOI

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    13
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  • Production of valuable chemicals from oil palm biomass using hot-compressed water method

    Ahmad T. Yuliansyah, Satoshi Kumagai, Tsuyoshi Hirajima, Keiko Sasaki

    Journal of Material Cycles and Waste Management   22 ( 6 ) 1859 - 1866  2020年11月

     概要を見る

    Oil palm industry discharges a large amount of biomass waste which can be converted into energy and chemicals. Hence, several biomass conversion methods are available, such as fermentation, pyrolysis, and gasification. In this work, the hot-compressed water method was proposed to produce valuable chemicals from oil palm biomass (oil palm fiber, shell, and empty fruit bunches). Each material was individually treated in a batch autoclave reactor at 200–300 °C for 30 min. After separation, the total organic carbon of the liquid product was measured by a Shimadzu TOC-5000A instrument, while its composition was analyzed by HPLC and GC/MC apparatus. Experimental results showed that liquid product of oil palm wastes contains various chemicals such as glucose, xylose, 5-HMF, furfural, acetic acid, formic acid, phenol, catechol, and phenol 2,6-di-methoxy. This liquid product composition was strongly dependent on the temperature treatment. In general, sugar-derived compounds (glucose, xylose, 5-HMF, furfural, acetic acid, formic acid) were primarily found in lower temperature
    meanwhile, lignin-derived compounds (phenol, catechol, and phenol 2,6-di-methoxy) were mainly obtained in higher temperature.

    DOI

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    1
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  • High-efficiency and low-carbon remediation of zinc contaminated sludge by magnesium oxysulfate cement

    Binglin Guo, Yongshan Tan, Lei Wang, Liang Chen, Zuliang Wu, Keiko Sasaki, Viktor Mechtcherine, Daniel C.W. Tsang

    Journal of Hazardous Materials   408   124486 - 124486  2020年11月  [査読有り]

    担当区分:責任著者

     概要を見る

    Electroplating sludge is classified as a hazardous waste due to its extremely high leachability of potentially toxic elements. This study concerns the use of magnesium oxysulfate cement (MOSC) for the stabilisation/solidification (S/S) of Zn-rich electroplating sludge. According to X-ray diffraction and thermogravimetric analyses, Zn was mainly immobilised through both chemical interaction and physical encapsulation in the MOSC hydrates of 5Mg(OH) ·MgSO .7H O (5−1−7) phase. The crystal size analysis, elemental mapping, and extended X-ray absorption fine structure (EXAFS) analysis proved that the Zn was also incorporated in the structure of 5–1–7 phase. Unlike Portland cement system, hydration kinetics, setting time, and compressive strength of the MOSC system were only negligibly modified by the presence of Zn, indicating its superior compatibility. Subsequent S/S experiments demonstrated that the MOSC binder exhibited an excellent performance on immobilisation efficiency of Zn (up to 99.9%), as well as satisfying the requirements of setting time and mechanical strength of sludge S/S products. Therefore, MOSC could be an effective and sustainable binder for the treatment of the Zn-rich industrial wastes. 2 4 2 2+

    DOI PubMed

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    69
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  • Bubble interactions with chalcopyrite and molybdenite surfaces in seawater

    Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Hajime Miki, Keiko Sasaki

    Minerals Engineering   157   106536 - 106536  2020年10月  [査読有り]

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    12
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  • Fabrication and characterization of ternary sepiolite/g-C3N4/Pd composites for improvement of photocatalytic degradation of ciprofloxacin under visible light irradiation

    Chitiphon Chuaicham, Radheshyam Rama Pawar, Sekar Karthikeyan, Bunsho Ohtani, Keiko Sasaki

    Journal of Colloid and Interface Science   577   397 - 405  2020年10月  [査読有り]

    担当区分:責任著者

     概要を見る

    The development of high-quality photocatalytic materials for the degradation of organic pollutants under visible light irradiation is a vital field of research. In the present study, a composite of natural sepiolite clay and synthetic graphitic carbon nitride (CN) mixed with dispersed palladium nanoparticles was developed for the efficient photocatalytic degradation of ciprofloxacin (CIP) under visible light irradiation. The sepiolite, CN, and composite materials were characterized by several techniques. The sepiolite/CN composite (SC30%) displayed superior activity than pristine sepiolite and CN, resulted from the generation of new electron trap states in the interfacial contract between sepiolite and CN to suppress the charge recombination of CN. Furthermore, the well-dispersed of 1 wt% Pd-nanoparticles in the SC30% composite collectively enhanced CIP degradation by avoiding the recombination of photogenerated electrons and holes. Additionally, the electron trap states on the surface of all samples were studied using novel reversed double-beam photoacoustic spectroscopy to understand electron transfer in the composites related to the photocatalytic degradation mechanism of CIP. The developed sepiolite/CN/Pd(0) composite can act as a potential catalyst for the degradation of organic pollutants in wastewater under visible light irradiation. (C) 2020 Elsevier Inc. All rights reserved.

    DOI

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    58
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  • Catalytic mechanism of activated carbon-assisted bioleaching of enargite concentrate

    Keishi Oyama, Kazuhiko Shimada, Jun-ichiro Ishibashi, Keiko Sasaki, Hajime Miki, Naoko Okibe

    HYDROMETALLURGY   196  2020年09月

     概要を見る

    The catalytic mechanism of activated carbon-assisted bioleaching of enargite concentrate (enargite 37.4%; pyrite 47.3%) was investigated by employing microbiological, electrochemical and kinetic studies. By using moderately thermophilic microorganisms at 45 degrees C, the final Cu dissolution was improved from 36% to 53% at 0.2% (w/v) activated carbon. An excess activated carbon addition showed an adverse effect. The enargite mineral itself favored higher solution redox potential (E-h) for solubilization. However, the dissolution of co-existing pyrite, which also favors high E-h, immediately hindered enargite dissolution through the passivation effect. The surface of activated carbon functioned as an electron mediator to couple RISCs oxidation and Fe3+ reduction, so that elevation of the E-h level was controlled by offsetting microbial Fe3+ regeneration. As long as the E-h level was suppressed at < 700 mV, the dissolution of pyrite was largely avoided, enabling a steady and continuous dissolution of the enargite mineral through the surface chemical reaction model. When the E-h-control by activated carbon becomes no longer sustainable and the E-h hits 700 mV, rapid pyrite dissolution was initiated and the surface chemical reaction of enargite dissolution came to an end. Arsenic species dissolved from enargite was constantly immobilized with an efficiency of 75-90% as amorphous ferric arsenate. However, the sudden initiation of pyrite dissolution also triggered the re-solubilization of ferric arsenate. Therefore, the sustainable E-h-controlling effect was shown to be critical to enable longer Cu dissolution from enargite as well as stabilization of As precipitates.

    DOI

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    5
    被引用数
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  • Effect of carbonaceous matter on bioleaching of Cu from chalcopyrite ore

    Kojo T. Konadu, Ryotaro Sakai, Diego M. Mendoza, Chitiphon Chuaicham, Hajime Miki, Keiko Sasaki

    Hydrometallurgy   195   105363 - 105363  2020年08月  [査読有り]

    担当区分:責任著者

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    6
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  • Co-sorption of Sr2+ and SeO<inf>4</inf>2− as the surrogate of radionuclide by alginate-encapsulated graphene oxide-layered double hydroxide beads

    Binglin Guo, Yuta Kamura, Paulmanickam Koilraj, Keiko Sasaki

    Environmental Research   187  2020年08月  [査読有り]

     概要を見る

    © 2020 Elsevier Inc. Graphene oxides (GO) and layered double hydroxides (LDHs) were applied to produce alginate beads for the remove of 90Sr2+ and 79SeO42−. The Freundlich isotherm indicated that the Sr2+ sorptions were based on the energetically heterogeneous multilayer surfaces. In contrast, the sorption behavior of SeO42− fitted to the Langmuir adsorption isotherm models, indicating that the removal of SeO42− was caused by the ion-exchange of LDHs. The synthesized LDH/GO alginates beads were also applied for setting up small-bore adsorption columns with loading synthetic SeO42− and Sr2+ contaminated wastewater. Based on the water chemistry, the adsorbed amount of Sr2+ significantly increased after using alginates beads, which was attributed to the functional groups of either GO or alginic acid. The incorporated SeO42− was highly depended on the contents of fabricated LDHs in alginate beads. Specifically, the adsorption capacity of Sr2+ (0.85–0.91 mmol/g) on GO slightly increased after alginates fabrication. Therefore, it was deduced that this layered material was partially exfoliated during the manufacture and thus increased the sorption sites. Applications of LDH/GO alginates beads in the removal of both Sr2+ and SeO42− in water and soil treatment have a significant impact on the environmental remediation.

    DOI PubMed

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    21
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  • Macroscopic and microscopic behaviors of Mn(II) (ad)sorption to goethite with the effects of dissolved carbonates under anoxic conditions

    Seonyi Namgung, Binglin Guo, Keiko Sasaki, Sang Soo Lee, Giehyeon Lee

    Geochimica et Cosmochimica Acta   277   300 - 319  2020年08月  [査読有り]

  • Effect of H2O2 and potassium amyl xanthate on separation of enargite and tennantite from chalcopyrite and bornite using flotation

    Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Hajime Miki, Keiko Sasaki, Shigeto Kuroiwa, Yuji Aoki

    Minerals Engineering   152   106371 - 106371  2020年06月  [査読有り]

    DOI

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    33
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  • Spectroscopic and first-principles investigations of iodine species incorporation into ettringite: Implications for iodine migration in cement waste forms

    Binglin Guo, Yihuang Xiong, Weinan Chen, Sarah A. Saslow, Naofumi Kozai, Toshihiko Ohnuki, Ismaila Dabo, Keiko Sasaki

    Journal of Hazardous Materials   389  2020年05月  [査読有り]

     概要を見る

    © 2019 Elsevier B.V. Low-level radioactive wastes are commonly immobilized in cementitious materials, where cement-based material can incorporate radionuclides into their crystal structure. Specifically, ettringite (Ca6Al2(OH)12(SO4)3∙26H2O) is known to stabilize anionic species, which is appealing for waste streams with radioactive iodine (129I) that persists as iodide (I–) and iodate (IO3–) in the cementitious nuclear waste repository. However, the structural information and immobilization mechanisms of iodine species in ettringite remain unclear. The present results suggested minimal I– incorporation into ettringite (0.05 %), whereas IO3– exhibited a high affinity for ettringite via anion substitution for SO42– (96 %). The combined iodine K-edge extended X-ray absorption fine structure (EXAFS) spectra and first-principles calculations using density functional theory (DFT) suggested that IO3– was stabilized in ettringite by hydrogen bonding and electrostatic forces. Substituting IO3– for SO42– was energetically favorable by –0.41 eV, whereas unfavorable substitution energy of 4.21 eV was observed for I– substitution. Moreover, the bonding charge density analysis of the substituted IO3– and I– anions into the ettringite structure revealed the interaction between intercalated ions with the structural water molecules. These results provided valuable insight into the long-term stabilization of anionic iodine species and their migration in cementitious nuclear waste repository or alkaline environments.

    DOI PubMed

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    49
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  • Immobilization mechanism of Se oxyanions in geopolymer: Effects of alkaline activators and calcined hydrotalcite additive

    Quanzhi Tian, Binglin Guo, Keiko Sasaki

    Journal of Hazardous Materials   387  2020年04月  [査読有り]

     概要を見る

    © 2019 Elsevier B.V. Geopolymers have been widely adopted to stabilize the cationic pollutants. However, few studies have focused on the immobilization of anionic species. In this study, the immobilization of SeO32– and SeO42– was explored for the first time using geopolymer activated by different alkaline solutions (NaOH and Na2SiO3) with and without calcined hydrotalcite (CHT), characterized by TCLP, XRD, FTIR, TG, NMR, XAFS, and N2 adsorption-desorption isotherm. Na2SiO3-activated geopolymers without CHT additive showed lower leaching percentages of SeO32– and SeO42– (approximately 10 % and 18 %) than NaOH-activated geopolymers (approximately 58 % and 74 %). It has been proven that electrostatic interaction is the main association mode of SeO32– and SeO42– in both NaOH- and Na2SiO3-activated geopolymers. Hence, compactness plays a vital role in the Se leaching from geopolymer. The addition of CHT reduced the compactnesses of both NaOH- and Na2SiO3-geopolymers. Due to the formation of hydrotalcite, the CHT additive contributed to immobilize SeO32– and SeO42– in NaOH-activated geopolymers. However, this phenomenon was not observed in Na2SiO3-activated geopolymers. Thus, the leaching amount of Se greatly increased from Na2SiO3-activated geopolymers with CHT additive. This study provides new insights on the application of geopolymer to immobilize anionic pollutants.

    DOI PubMed

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    46
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  • Stabilization of borate by hot isostatic pressing after coprecipitation with hydroxyapatite using MAP

    Keiko Sasaki, Yoshikazu Hayashi, Takeshi Nakamura, Binglin Guo, Quanzhi Tian

    Chemosphere    2020年04月  [査読有り]

    担当区分:筆頭著者, 最終著者, 責任著者

  • Self-tuning tetragonal zirconia-based bimetallic nano(hydr)oxides as superior and recyclable adsorbents in arsenic-tolerant environment: Template-free in and ex situ synthetic methods, stability, and mechanisms

    Subbaiah Muthu Prabhu, Keiko Sasaki, S.S D. Elanchezhiyan, G. Paruthimal Kalaignan, Chang Min Park

    Chemical Engineering Journal    2020年02月  [査読有り]

  • Synergistic effect of ClO4- and Sr2+ adsorption on alginate-encapsulated organo-montmorillonite beads: Implication for radionuclide immobilization

    Wuhui Luo, Qidong Huang, Philip Antwi, Binglin Guo, Keiko Sasaki

    JOURNAL OF COLLOID AND INTERFACE SCIENCE   560   338 - 348  2020年02月  [査読有り]

     概要を見る

    Perchlorate (ClO4-) and pertechnetate (TcO4-) exhibit similar adsorption characteristics on alkyl quaternary ammonium-modified montmorillonite (Mt), and (TcO4-)-Tc-99m normally coexists with Sr-90(2+) in radionuclide-contaminated water. In this study, hexadecyl pyridinium (HDPy)-modified Mt (OMt) was encapsulated in alginate beads to inhibit HDPy release and simultaneously immobilize ClO4- and Sr2+ ions. The release of HDPy was remarkably reduced (78 times) from OMt after alginate encapsulation. Adsorption of ClO4- and Sr2+ on the obtained composite demonstrated synergistic effects, with adsorption capacities reaching 0.542 and 0.484 mmol/g, respectively. Compared to the single-adsorbate system, adsorption capacities of ClO4- and Sr2+ increased significantly. The characterization of solids using X-ray diffraction, Fourier transform infrared spectroscopy, C-13 nuclear magnetic resonance, and X-ray photoelectron spectroscopy, as well as the chemical analysis of the aqueous solution, demonstrated that HDPy+-COO- disintegration accounted for the adsorption synergy. HDPy was extracted from the Mt interlayer space during the synthesis of OMt/alginate and then partially re-intercalated back after interacting with ClO4- during the adsorption of ClO4- and/or Sr2+. In the binary-adsorbate system, the synergy-induced adsorption capacity was superior to many previously reported adsorbents, implying that OMt/alginate beads can be a promising adsorbent for the remediation of aqueous solutions contaminated with multiple radionuclides. (C) 2019 Elsevier Inc. All rights reserved.

    DOI

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  • Energy-resolved distribution of electron traps for O/S-doped carbon nitrides by reversed double-beam photoacoustic spectroscopy and the photocatalytic reduction of Cr(VI)

    Chitiphon Chuaicham, Radheshyam R Pawar, Karthikeyen Sekar, Yihuang Xiong, Ismaila Dabo, Bunsho Ohtani, Keiko Sasaki

    Chemical Communications   56 ( 26 ) 3793 - 3796  2020年02月  [査読有り]

     概要を見る

    We report for the first time to our knowledge the identification of heteroatom-doped and undoped C3N4 with the energy-resolved distribution of electron traps (ERDT) near the conduction band bottom position (CBB) using reversed double-beam photoacoustic spectroscopy. The ERDT/CBB pattern is used to classify the type of elemental doping in C3N4, related to photocatalytic efficiency.

    DOI

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    31
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  • Importance of ZnTiO3 phase in ZnTi mixed metal oxide photocatalyst derived from layered double hydroxide,

    Chitiphon Chuaicham, Karthikeyen Sekar, Jun Tae Song, Tatsumi Ishihara, Bunsho Ohtani, Keiko Sasaki

    ACS Applied Materials & Interfaces   12 ( 8 ) 9169 - 9180  2020年02月  [査読有り]

    担当区分:責任著者

     概要を見る

    In this study, ZnTi-mixed metal oxides (ZTM), such as ZnTiO3, were synthesized from ZnTi layered double hydroxides by varying the molar ratio of Zn/Ti, calcination temperatures, and synthesis methods (hydrothermal or reflux). The surface electronic characteristics of ZTM were investigated by the energy-resolved distribution of electron traps (ERDTs) using reversed double-beam photoacoustic spectroscopy. The ZTM samples obtained by conducting hydrothermal synthesis at 500 degrees C showed similar ERDT patterns independent of the molar ratio of Zn/Ti, although ZnTiO3 phase was not observed in the X-ray diffraction pattern, when the Zn/Ti ratio was high. When the ERDT patterns demonstrated a high electron accumulation level near the conduction band bottom in hydrothermal products at 500 degrees C, a higher photocatalytic phenol degradation efficiency was observed due to the formation of ZnTiO3 phase. This suggested that the product with the high Zn/Ti molar ratio (Zn/Ti = 6) constituted amorphous ZnTiO3.The enhanced photocatalytic performance of ZTM could be attributed to the heterojunction of electrons among ZnO, TiO2, and ZnTiO3, which enabled electron transfer in the composites, prevented charge recombination, and promoted a wider visible light adsorption by ZnTiO3 phase irrespective of its crystallinity.

    DOI

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    40
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  • Mechanism analysis of selenium (VI) immobilization using alkalineearth metal oxides and ferrous salt

    Quanzhi Tian, Binglin Guo, Chitiphon Chuaicham, Keiko Sasaki

    Chemosphere    2020年01月  [査読有り]

    担当区分:最終著者, 責任著者

  • Nanoscale Materials with Different Dimensions for Advanced Electrocatalysts

    in “Nanomaterials for sustainable energy and environmental remediation", edited by John Irvine, Mu. Naushad, R. Saravanan, Kumar Raju, Elsevier    2020年  [査読有り]

  • Addition of calcined hydrotalcite into geopolymer pastes activated by different alkaline solutions for immobilization of selenium: influence and mechanism analysis

    J. Hazard. Mater.   387   121994  2020年  [査読有り]

    担当区分:責任著者

  • Pompon Dahlia-like Cu2O/rGO nanostructures for visible light photocatalytic H2 production and 4-chlorophenol degradation

    Chem Cat Chem   12 ( 6 ) 1699 - 1709  2020年01月  [査読有り]

    DOI

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    31
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  • Understanding the specific functional groups in humic acid affecting the sorption mechanism of different calcinated layered double hydroxides

    Chemical Engineering Journal    2020年  [査読有り]

    担当区分:最終著者, 責任著者

  • A novel composite of layered double hydroxide/geopolymer for co-immobilization of Cs+ and SeO<inf>4</inf>2− from aqueous solution

    Tian, Q., Sasaki, K.

    Science of the Total Environment   695  2019年12月  [査読有り]

    DOI

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    33
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  • Effect of Natural Organic Matter Model Compounds on the Structure Memory Effect of Different Layered Double Hydroxides

    Shuang Xu, Jiawen Zhao, Qianqian Yu, Xinhong Qiu, Keiko Sasaki

    ACS Earth and Space Chemistry   3 ( 10 ) 2175 - 2189  2019年10月  [査読有り]

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    20
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  • Arginine and lysine-functionalized layered double hydroxides as efficient sorbents for radioactive Co2+ removal by chelate-facilitated immobilization

    Koilraj, P., Kalusulingam, R., Sasaki, K.

    Chemical Engineering Journal   374   359 - 369  2019年10月  [査読有り]

    DOI

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    36
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  • Immobilization of cesium in fly ash-silica fume based geopolymers with different Si/Al molar ratios

    Tian, Q., Nakama, S., Sasaki, K.

    Science of the Total Environment   687   1127 - 1137  2019年10月  [査読有り]

    DOI

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    50
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  • Template free mild hydrothermal synthesis of core-shell Cu2O(Cu)@CuO visible light photocatalysts for N-acetyl-para-aminophenol degradation

    Karthikeyan Sekar, Chuaicham Chitiphon, Pawar Radheshyam R, Sasaki Keiko, Li Wei, Lee Adam F, Wilson Karen

    JOURNAL OF MATERIALS CHEMISTRY A   7 ( 36 ) 20767 - 20777  2019年09月  [査読有り]

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    46
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  • Production of highly catalytic, archaeal Pd(0) bionanoparticles using Sulfolobus tokodaii.

    Santisak Kitjanukit, Keiko Sasaki, Naoko Okibe

    Extremophiles : life under extreme conditions   23 ( 5 ) 549 - 556  2019年09月  [査読有り]  [国際誌]

     概要を見る

    The thermo-acidophilic archaeon, Sulfolobus tokodaii, was utilized for the production of Pd(0) bionanoparticles from acidic Pd(II) solution. Use of active cells was essential to form well-dispersed Pd(0) nanoparticles located on the cell surface. The particle size could be manipulated by modifying the concentration of formate (as electron donor; e-donor) and by addition of enzymatic inhibitor (Cu2+) in the range of 14-63 nm mean size. Since robust Pd(II) reduction progressed in pre-grown S. tokodaii cells even in the presence of up to 500 mM Cl-, it was possible to conversely utilize the effect of Cl- to produce even finer and denser particles in the range of 8.7-15 nm mean size. This effect likely resulted from the increasing stability of anionic Pd(II)-chloride complex at elevated Cl- concentrations, eventually allowing involvement of greater number of initial Pd(0) crystal nucleation sites (enzymatic sites). The catalytic activity [evaluated based on Cr(VI) reduction reaction] of Pd(0) bionanoparticles of varying particle size formed under different conditions were compared. The finest Pd(0) bionanoparticles obtained at 50 mM Cl- (mean 8.7 nm; median 5.6 nm) exhibited the greatest specific Cr(VI) reduction rate, with four times higher catalytic activity compared to commercial Pd/C. The potential applicability of S. tokodaii cells in the recovery of highly catalytic Pd(0) nanoparticles from actual acidic chloride leachate was, thus, suggested.

    DOI PubMed

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    3
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  • Transformation of the carbonaceous matter in double refractory gold ore by crude lignin peroxidase released from the white-rot fungus

    Konadu, K.T., Harrison, S.T.L., Osseo-Asare, K., Sasaki, K.

    International Biodeterioration and Biodegradation   143  2019年09月  [査読有り]

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    18
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  • A mechanistic investigation of highly stable nano ZrO<inf>2</inf> decorated nitrogen-rich azacytosine tethered graphene oxide-based dendrimer for the removal of arsenite from water

    Prabhu, S.M., Pawar, R.R., Sasaki, K., Park, C.M.

    Chemical Engineering Journal   370   1474 - 1484  2019年08月  [査読有り]

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    21
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  • Energy-resolved distribution of electron traps study for ZnTi mixed metal oxides as photocatalysts to degrade phenol

    Chitiphon Chuaicham, Keiko Sasaki

    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY   258  2019年08月

  • Application of fly ash-based materials for stabilization/solidification of cesium and strontium

    Tian, Q., Sasaki, K.

    Environmental Science and Pollution Research   26 ( 23 ) 23542 - 23554  2019年08月  [査読有り]

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    29
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  • ハイドロキシアパタイト共沈法による坑廃水中のホウ酸およびヒ酸の同時除去のパイロット試験への応用

    林良和, 郭柄霖, 平島剛, 伊藤竜也, 中村壮志, 笹木圭子

    Journal of MMIJ    2019年07月  [査読有り]

  • Sequential pretreatment of double refractory gold ore (DRGO)with a thermophilic iron oxidizing archeaon and fungal crude enzymes

    Konadu, K.T., Huddy, R.J., Harrison, S.T.L., Osseo-Asare, K., Sasaki, K.

    Minerals Engineering   138   86 - 94  2019年07月  [査読有り]

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    31
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  • Characterizations of calcium silicate hydrates derived from coal fly ash and their mechanisms for phosphate removal

    Tian, Q., Sasaki, K.

    Desalination and Water Treatment   156   78 - 86  2019年07月  [査読有り]

    DOI

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  • Suppression processes of anionic pollutants released from fly ash by various Ca additives

    Binglin Guo, Shingo Nakama, Quanzhi Tian, Niko Dian Pahlevi, Zhaochu Hu, Keiko Sasaki

    JOURNAL OF HAZARDOUS MATERIALS   371   474 - 483  2019年06月  [査読有り]

     概要を見る

    Harmful trace elements, which are initially included in the coal fly ash, have the potential to be leached when coal fly ash comes in contact with water. This causes a risk of pollutant species being released, considering the long lifetime of building structures where coal fly ash was applied. Some Ca additives effectively function to suppress the release of anionic pollutants; however, the detailed suppression processes remains unclear. In this work, the influences of various Ca additives on the released anionic pollutants (B, F, S, As, and Cr) was systematically investigated. According to the comprehensive results of solution data with the solid characterization, the 60% hydroxylated calcined dolomite (HCD 60) was the best Ca additive for the suppression of different anionic pollutants since this Ca source not only simply provides an alkaline reagent but also supplies MgO and Mg(OH)(2), which affect the phase transformation that accompanies with hydration. The phase transformation occurs from Ca(OH)(2) to ettringite via hydrocalumite, which is the most important suppression processes of released pollutants. The precipitation of Ca salts is another pathway to immobilize these pollutants. In this scheme, MgO and Mg(OH)(2) were proven to enhance the formation of ettringite and hydrocalumite, respectively.

    DOI

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    40
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  • 25
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  • Double-Edged Effect of Humic Acid on Multiple Sorption Modes of Calcined Layered Double Hydroxides: Inhibition and Promotion

    Xinhong Qiu, Keiko Sasaki, Shuang Xu, Jiawen Zhao

    Langmuir   35 ( 19 ) 6267 - 6278  2019年05月  [査読有り]

    DOI

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    12
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  • Synthesis of modulator-driven highly stable zirconium-fumarate frameworks and mechanistic investigations of their arsenite and arsenate adsorption from aqueous solutions

    Subbaiah Muthu Prabhu, Srinivasarao Kancharla, Chang Min Park, Keiko Sasaki

    CrystEngComm   21 ( 14 ) 2320 - 2332  2019年04月  [査読有り]

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    31
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  • Mono-, Di-, and Tricarboxylic Acid Facilitated Lanthanum-Based Organic Frameworks: Insights into the Structural Stability and Mechanistic Approach for Superior Adsorption of Arsenate from Water

    Subbaiah Muthu Prabhu, Shunsuke Imamura, Keiko Sasaki

    ACS Sustainable Chemistry & Engineering   7 ( 7 ) 6917 - 6928  2019年04月  [査読有り]

    DOI

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    103
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  • Acid tolerant covalently functionalized graphene oxide for the selective extraction of Pd from high-level radioactive liquid wastes

    Srinivasarao Kancharla, Keiko Sasaki

    Journal of Materials Chemistry A   7 ( 9 ) 4561 - 4573  2019年03月  [査読有り]

    DOI

  • Dye-sensitized photocatalyst of sepiolite for organic dye degradation

    Chuaicham, C., Pawar, R., Sasaki, K.

    Catalysts   9 ( 3 )  2019年03月  [査読有り]

    DOI

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    37
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  • Reduction of undesirable element leaching from fly ash by adding hydroxylated calcined dolomite

    Quanzhi Tian, Binglin Guo, Shingo Nakama, Li Zhang, Zhaochu Hu, Keiko Sasaki

    WASTE MANAGEMENT   86   23 - 35  2019年03月  [査読有り]

     概要を見る

    Fly ash always contains many toxic elements which can be released into environment, thereby easily leading to environmental contaminations. In order to dispose fly ash safely, related strategies are needed. In this investigation, two kinds of hydroxylated calcined dolomites (HCD60 and HCD100) were used as the additives and compared with lime on the leachabilities of anionic species from fly ash. Both additives were found effective in reducing the leaching concentrations of these elements, which was better than that of only lime addition. Mg(OH)(2) and MgO were believed to play important roles in the hydration reaction of fly ash. In the presence of Mg(OH)(2) and MgO, there were more hydration products including calcium silicate hydrate, ettringite, hydrocalumite and other Layered double hydroxides (LDHs) generated which were effective candidates for anion removal. Thus, the final leaching results were controlled by these newly formed phases through adsorption, incorporation or encapsulation. On the other hand, compared with Mg(OH)(2), MgO can promote the formation of hydration products in a larger extent because of the hydration process of MgO into Mg(OH)(2). There was no systematic trend in the promotion of fly ash hydration by Mg(OH)(2) or MgO because it had a close relationship with the properties of original fly ash. Objectively, hydroxylated calcined dolomites can be promising candidate additives for reduction of toxic elements leaching from fly ash. (C) 2019 Elsevier Ltd. All rights reserved.

    DOI

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    27
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  • Hydrothermal treatment of oil palm biomass in batch and semi-flow reactors

    Ahmad T. Yuliansyah, Satoshi Kumagai, Tsuyoshi Hirajima, Keiko Sasaki

    Energy Procedia   158   675 - 680  2019年

     概要を見る

    Oil palm frond and empty fruit bunch (EFB), which were abundant biomass resources found in Indonesia, were hydrothermally-treated using two different types of reactor, e.g. batch and semi-flow reactor. The objective of this research was to make a comparison of product resulted from both types of treatment. Based on the experimental results, it was found that liquefaction of biomass material occurred more effectively in semi-flow reactor. Semi-flow reactor facilitated a higher recovery of several sugar compounds such as xylooligosaccharides and arabinose. On the hand, residual solids from batch treatment had higher theoretical calorific values (18.81 and 18.00 MJ/kg) than those from semi-flow (15.40 and 17.41 MJ/kg, for frond and EFB respectively).

    DOI

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    5
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  • Investigation of reagents for selective flotation on chalcopyrite and molybdenite

    H. Miki, T. Hirajima, Y. Muta, G. P.W. Suyantara, K. Sasaki

    IMPC 2018 - 29th International Mineral Processing Congress     1854 - 1861  2019年

     概要を見る

    Selective flotation of chalcopyrite and molybdenite is continuing problem since its selectivity is not perfect and current NaHS process needs closed system flotation plant because of hydrogen sulfide emission on acidic condition. Some alternative additives investigated as chalcopyrite became hydrophilic and molybdenite kept hydrophobic. XPS analysis indicated chalcopyrite became hydrophilic since iron and copper sulphate, hydroxide was covered on the surface whereas molybdenite kept hydrophobic since only molybdenite can be seen. Flotation experiments of chalcopyrite and molybdenite mixture sample indicated excellent separation that 95% of molybdenite can be recovered as froth and 93% of chalcopyrite can be recovered as sink. Flotation experiments with real bulk flotation concentration indicated similar separation result compared with current NaHS additive system. Possible mechanisms and detailed phenomenon were investigated based on the surface analysis and thermodynamic calculation etc. this alternative additive is easy to handle compared with NaHS since it does not emit effluent gas and commercially preferable.

  • The use of Fenton's reagent on selective flotation of chalcopyrite and molybdenite

    Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Hajime Miki, Keiko Sasaki

    IMPC 2018 - 29th International Mineral Processing Congress     1862 - 1871  2019年

     概要を見る

    Hydrogen peroxide (H 2 O 2 ) is frequently used as an oxidizing agent in various applications. It has also been reported to reduce the recovery of sulfide minerals. Moreover, the previous work applied H 2 O 2 aqueous solution in selective flotation of chalcopyrite and molybdenite. However, the oxidation method suffered in pilot scale test due to too long conditioning time. Furthermore, the excessive reagent consumption increased the reagent cost, causing the method not economically feasible. Consequently, further improvement is required to reduce the conditioning time and the reagent consumption. The oxidation performance of H 2 O 2 can be improved by using ferrous iron as catalyst, producing a Fenton's reagent which is more powerful oxidizer than the H 2 O 2 itself. Therefore, the effect of Fenton's reagent on the floatability of chalcopyrite and molybdenite was investigated in this study. The flotation test results show that selective flotation of chalcopyrite and molybdenite might be possible at low concentration of H 2 O 2 aqueous solution by adding ferrous iron. Moreover, the conditioning time could be shortened by this improvement. To understand the phenomenon, surface characterization using atomic force microscopy (AFM) along with x-ray photoelectron spectroscopy (XPS) analysis were carried out. The AFM images show that the surface of chalcopyrite was readily covered with mountainous features which alters its hydrophobicity after the oxidation treatment. Meanwhile, the molybdenite surface remained clean and relatively hydrophobic. The XPS results indicate that the mountainous features are various oxidation products (i.e., FeOOH, Fe 2 (SO 4 ) 3 , CuO, Cu(OH) 2 ). Possible mechanisms of this phenomenon were proposed in this work.

  • Cosorption Characteristics of SeO42– and Sr2+ Radioactive Surrogates Using 2D/2D Graphene Oxide-Layered Double Hydroxide Nanocomposites

    Paulmanickam Koilraj, Yuta Kamura, Keiko Sasaki

    ACS Sustainable Chemistry & Engineering   6 ( 11 ) 13854 - 13866  2018年11月  [査読有り]

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    28
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  • Effect of Fenton-like oxidation reagent on hydrophobicity and floatability of chalcopyrite and molybdenite

    Suyantara, G.P.W., Hirajima, T., Miki, H., Sasaki, K., Yamane, M., Takida, E., Kuroiwa, S., Imaizumi, Y.

    Colloids and Surfaces A: Physicochemical and Engineering Aspects   554   34 - 48  2018年10月  [査読有り]

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    46
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  • Enhanced adsorption of perchlorate by gemini surfactant-modified montmorillonite: Synthesis, characterization and their adsorption mechanism

    Srinivasarao, K., Prabhu, S.M., Luo, W., Sasaki, K.

    Applied Clay Science   163   46 - 55  2018年10月  [査読有り]

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    31
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  • Distributions and Leaching Behaviors of Toxic Elements in Fly Ash

    Quanzhi Tian, Binglin Guo, Shingo Nakama, Keiko Sasaki

    ACS OMEGA   3 ( 10 ) 13055 - 13064  2018年10月  [査読有り]

     概要を見る

    Fly ash usually contains a considerable amount of toxic elements that can be leached into the environment, thereby easily leading to serious contaminations. In this work, the leaching behaviors of poisonous elements including boron (B), phosphoms (P), vanadium (V), chromium (Cr) arsenic (As), selenium (Se), inolybdenum (Mo), antimony (Sb), and tungsten (W) from fly ash were explored by sequential' extraction. Importantly, the associations of these elements in fly ash were discussed based on their leaching and X-ray absorption near-edge structure (XANES) results. From the XANES results it was observed that V(IV), Cr(III) As(V), Se(IV), and W(IV) were their main states of existence in fly ash. In terms of leaching results, large amounts of Mo and W were leached into pure water, which indicated their high mobilities. Furthermore, the occurrence of Mo in fly ash was mainly in the form of oxides, and W had complex associations including WX4 (X can be monovalent anions), its reduction state or association with the elements that can be oxidized, and existence in silicates. B was as easily released into the environment as Mo and W. It can have several associations with the other cations, such as Ca2+, Na+, and Mg2+, and occurs in silicates. In contrast, most of the Cr and Sb were locked in silicates, indicating that they were very stable in fly ash. In addition, P, V, and As can exist within the structure of silicates as well. However, a considerable amount of them leached in the reduction step with a low pH. Hence, they can be associated with Ca2+, Na+, Mg2+, or Fe3+. In terms of Se, oxidation processes played an important role in controlling its leaching because of the oxidation of Se(IV) to Se (VI). Calcium selenite should be the predominant form of Se in fly ash.

    DOI

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    54
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  • Microbiological Redox Potential Control to Improve the Efficiency of Chalcopyrite Bioleaching

    Yusei Masaki, Tsuyoshi Hirajima, Keiko Sasaki, Hajime Miki, Naoko Okibe

    Geomicrobiology Journal   35 ( 8 ) 648 - 656  2018年09月  [査読有り]

     概要を見る

    © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group. The effect of controlling the redox potential (Eh) on chalcopyrite bioleaching kinetics was studied as a new aspect of redox control during chalcopyrite bioleaching, and its mechanism was investigated by employing the “normalized” solution redox potential (Enormal) and the reaction kinetics model. Different Eh ranges were established by use of different acidophiles (Sulfobacillus acidophilus YTF1; Sulfobacillus sibiricus N1; Acidimicrobium ferrooxidans ICP; Acidiplasma sp. Fv-AP). Cu dissolution was very susceptible to real-time change in Eh during the reaction. It was found that efficiency of bioleaching of chalcopyrite can be effectively evaluated on the basis of Enormal, since it is normalized for real-time fluctuations of concentrations of major metal solutes during bioleaching. For steady Cu solubilization during bioleaching at a maximum rate, it was important to maintain a redox potential range of 0 ≤ Enormal ≤ 1 (−0.35 mV optimal) at the mineral surface by employing a “weak” ion-oxidizer. This led to a copper recovery of > 75%. At higher Enormal levels (Enormal > 1 by “strong” microbial Fe2+ oxidation), Cu solubilization was slowed by diffusion through the product film at the mineral surface (< 50% Cu recovery) caused by low reactivity of the chalcopyrite and by secondary passivation of the chalcopyrite surface, mainly by jarosite.

    DOI

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  • Simultaneous immobilization of borate, arsenate, and silicate from geothermal water derived from mining activity by co-precipitation with hydroxyapatite

    Keiko Sasaki, Yoshikazu Hayashi, Kenta Toshiyuki, Binglin Guo

    CHEMOSPHERE   207   139 - 146  2018年09月  [査読有り]

     概要を見る

    The treatment of the geothermal water discharged through mining activity is a critical issue because the rate of discharge is 12,000 m(3) per day and the discharge contains high concentrations of borate (>20 mg/ L) and arsenate (ca.0.4 mg/L) as well as silicate and carbonate. The simultaneous reduction of borate and arsenate concentrations to acceptable levels was successfully performed by co-precipitation with hydroxyapatite (HAp). Although the coexisting high concentrations of carbonate act as a disturbing element, the co-precipitation equilibrium of borate was shifted to lower values by adjusting the P/Ca molar ratio, and the removal rate of borate was accelerated by using A(13+)additives, resulting in the efficient reduction of borate within 1 h. The initially immobilized boron in HAp is in the tetragonal form, which probably occupies the hydroxyl sites in HAp, gradually transforming into the trigonal form in the solid state, as interpreted by H-1 NMR and B-11-NMR. The coexisting silicate was also immobilized in an ellestadite form, as confirmed by Si-29-NMR measurements. Arsenate and silicate were immobilized before borate in geothermal water. A dissolution assay of borate in the solid residues after co-precipitation with HAp verified the acceptable stability of borate, which is independent of the amount of added A1(3+). (C) 2018 Elsevier Ltd. All rights reserved.

    DOI

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    16
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  • Behavior of sulfate ions during biogenic scorodite crystallization from dilute As(III)-bearing acidic waters

    Tanaka, Masahito, Sasaki, Keiko, Okibe, Naoko

    HYDROMETALLURGY   180   144 - 152  2018年09月  [査読有り]

     概要を見る

    This study revealed the importance of SO42- ions during biogenic scorodite crystallization via a two-stage As removal process, using a combination of liquid and solid analyses (chemical digestion, FT-IR, SEM, TG-DTA, particle distribution). The first-stage As-removal was induced by microbial oxidation of Fe2+ and As(III), precipitating SO42- bearing amorphous precursors composed of basic ferric sulfate (MFex(SO4)(y)(OH)(z)) and ferric arsenate (FeAsO4 center dot(2 + n)H2O). This was followed by an induction period (a period of constant concentration), where dissolution-recrystallization of unstable amorphous precursors proceeded: Re-dissolved metal ions became locally concentrated on the surface of precursors, which gave the driving force for the second-stage As removal as secondary layers of crystalline biogenic scorodite (Fe(AsO4)(0.94)(SO4)(0.08)center dot 1.69H(2)O) out of even more dilute and seeded solution. This phase transformation process was also accompanied by continuous dehydration. This two-stage As-removal via SO42- mediated phase transformation was shown to be key to promote biogenic scorodite formation with greater final As-removal from dilute As(III)-bearing solutions.

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  • Selective flotation of chalcopyrite and molybdenite using H2O2 oxidation method with the addition of ferrous sulfate

    Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Hajime Miki, Keiko Sasaki, Masashi Yamane, Eri Takida, Shigeto Kuroiwa, Yuji Imaizumi

    Minerals Engineering   122   312 - 326  2018年06月  [査読有り]

     概要を見る

    Hydrogen peroxide (H2O2) has been used as an oxidizing agent in the selective flotation of chalcopyrite and molybdenite. However, this method required relatively high concentration of H2O2 to deliver flotation results (i.e., mineral grades and recoveries) comparable to those obtained by the conventional copper-molybdenum (Cu-Mo) ores flotation using sodium hydrosulfide (NaHS). Therefore, further improvements are needed to reduce the consumption of H2O2 reagent. In this study, ferrous sulfate (FeSO4) was used to enhance the oxidation performance of H2O2 through Fenton-like reactions. Flotation results showed that the consumption of H2O2 reagent could be reduced by the addition of FeSO4 without losing the flotation selectivity. The reason might be caused by increasing of oxidation performance as indicated by the increasing concentration of dissolved oxygen after the addition of FeSO4 into the H2O2 aqueous solution. Surface analysis using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) images showed that the surface of chalcopyrite was covered by more hydrophilic precipitates after the oxidation treatment using H2O2 aqueous solution with the addition of FeSO4, thus more hydrophilic surface and lower floatability. On the other hand, the surface of molybdenite was slightly oxidized and its surface remained hydrophobic as confirmed from contact angle results. Flotation tests using Cu-Mo bulk concentrate demonstrated that selective flotation might be possible using a mixture of FeSO4 and H2O2 aqueous solution. Moreover, this new method could be used as an alternative to copper depressant in Cu-Mo selective flotation, replacing the NaHS reagent.

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  • Structural Memory Effect of Mg-Al and Zn-Al layered Double Hydroxides in the Presence of Different Natural Humic Acids: Process and Mechanism

    Zhisheng Gao, Keiko Sasaki, Xinhong Qiu

    Langmuir   34 ( 19 ) 5386 - 5395  2018年05月  [査読有り]

     概要を見る

    The structural memory effect of layered double hydroxides (LDHs) is one of the important reasons for their extensive use in environmental remediation. In this study, humic acid (HA) was extracted from black soil and sediments and characterized to determine their structures. The regeneration mechanisms of calcinated LDHs (CLDHs) including different divalent metals (Mg-CLDH and Zn-CLDH) in deionized water and different HA solutions were carefully elucidated, and the reasons for the behavior differences in the two materials were explained. The presence of the HAs significantly increased the dissolution rate of Mg2+ ions from Mg-CLDHs and subsequent regeneration of Mg-LDH. Because of the diverse functional groups in the HAs, these groups were complexed with metallic ions such as Mg2+ on the surface of Mg-CLDH in the beginning. During the process, the HAs adsorbed the regenerated LDHs on the surfaces. Therefore, the crystallinity, morphology, and specific surface area of the regenerated Mg-LDH significantly changed, especially in the presence of high concentrations of HA. In the case of Zn-CLDH, the regeneration rate of the LDH increased in the presence of HA, but the surface of Zn-CLDH was covered with regenerated Zn-LDH and HA. Then, the inside of the particles could not transform to LDH, leading to poor crystallinity and a significant increase in the ZnO content of the HA system.

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    84
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  • A Mechanistic Approach for the Synthesis of Carboxylate-Rich Carbonaceous Biomass-Doped Lanthanum-Oxalate Nanocomplex for Arsenate Adsorption

    Subbaiah Muthu Prabhu, Chitiphon Chuaicham, Keiko Sasaki

    ACS Sustainable Chemistry and Engineering   6 ( 5 ) 6052 - 6063  2018年05月  [査読有り]

     概要を見る

    Considering the protocol of "zero-alkaline waste disposal" for green and arsenic-free environment, lanthanum (La3+)-based MOF-like complex materials were designed, and the complex materials have been employed as adsorbent for AsO4 3- adsorption from water. The sucrose-derived porous carbon (SPC)@La-oxalate complex was prepared by a simple one-pot coprecipitation method at room temperature, where oxalate has been used as an organic ligand, and the carbonaceous biomass has been used as a doping material that is naturally a carboxylate-rich functional group derived from a sucrose biomass. In addition to SPC@La-oxalate, bare-SPC, La(OH)3, and SPC@La(OH)3 were also prepared via simple base-addition conventional methods, and their performances in AsO4 3- removal were compared. The FTIR peak at 848 cm-1 confirmed the presence of AsO4 3- on the SPC@La-oxalate complex after adsorption of 1 mM AsO4 3-. The high resolution X-ray photoelectron spectrum for the AsO4 3- adsorbed SPC@La-oxalate showed a peak at EB[As 3d] = 45.2 eV, which could be attributed to As5+. The EXAFS of the As K-edge revealed that there are two distinct atomic shells, As-O with the distance of 1.68 Å and As-La with the distance of 3.32 Å, indicating the formation of monodentate complex of La with AsO4 3-. Additionally, an electrostatic interaction and hydrogen bonding are also possible adsorption mechanism in acidic conditions. The SPC@La-oxalate complex adsorbent showed excellent dearsenate behavior of 1.093 mmol/g, and the maximum AsO4 3- removal was maintained in a wide pH range from 3 to 8. Sorption kinetic data were the best expressed by a pseudo-second-order rate equation, and the maximum adsorption capacity was 1.858 mmol/g based on Langmuir monolayer adsorption. Compared with previous reports, SPC@La-oxalate adsorbent could be easily prepared, and the uptake amounts for AsO4 3- were enriched. Reusability of the material after six cycles is yet another advantage to the present adsorbent. This work will help to facilitate the research on novel complex adsorbents for the removal of AsO4 3- from water.

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  • Immobilization of selenate in cancrinite using a hydrothermal method

    Niko Dian Pahlevi, Binglin Guo, Keiko Sasaki

    CERAMICS INTERNATIONAL   44 ( 7 ) 8635 - 8642  2018年05月  [査読有り]

     概要を見る

    Because of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, radioactive species were leaked out, including selenium isotopes (Se-79). Developing a stable matrix that is suitable for longterm storage is necessary for the decommissioning process of the FDNPP. In the present work, the co-precipitation of SeO42- in cancrinite/sodalite as a potential stable matrix was investigated at various reaction times using a hydrothermal method. Over time, the SeO42- contents in the solid products gradually increased. The XRD patterns revealed that the reaction produced multi-phased precipitates, which were zeolite Na (P), sodalite, and cancrinite. As the SeO42- amount increased, the solid products were transformed to cancrinite. The calculated lattice parameter of sodalite and cancrinite showed an increase in lattice parameter a for sodalite and cancrinite, suggesting SeO42- incorporated into the sodalite/cancrinite structure. XRD, SEM, FTIR, Al-27-NMR, and Si-29-NMR results revealed the phase transformation of the solid products over time. Four stages of the co-precipitation mechanism are proposed, including the formation of zeolite P (Na), hydroxylation of zeolite P (Na), the formation of sodalite, and cancrinite reprecipitation.

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    15
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  • Effect of sodium sulfite on floatability of chalcopyrite and molybdenite

    Hajime Miki, Tsuyoshi Hirajima, Yukihiro Muta, Gde Pandhe Wisnu Suyantara, Keiko Sasaki

    Minerals   8 ( 4 )  2018年04月  [査読有り]

     概要を見る

    Sodium hydrogen sulfide (NaHS) is commonly used as a copper depressant in the selective flotation of copper and molybdenum ores. However, the process is facing health and safety issues because NaHS readily yields toxic hydrogen sulfide gas (H2S) under acidic conditions. In this study, Na2SO3 was proposed as an alternative copper depressant. The effect of Na2SO3 on the surface wettability and floatability of chalcopyrite and molybdenite—typical copper and molybdenum minerals, respectively—was intensively studied using contact angle measurements and flotation tests. Contact angle readings show that the chalcopyrite surface became hydrophilic after the Na2SO3 treatment. Meanwhile, the molybdenite surface was relatively more hydrophobic compared with that of chalcopyrite after the treatment. Flotation tests using pure minerals of chalcopyrite and molybdenite demonstrate that the floatability of chalcopyrite decreased with increasing concentration of Na2SO3. On the other hand, the floatability of molybdenite gradually increased under similar conditions, suggesting that Na2SO3 might have the potential to be used for selective flotation of chalcopyrite and molybdenite. A possible mechanism is proposed in this study to explain the phenomenon using X-ray photoelectron spectroscopy analysis.

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    25
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  • Effects of precursors on the photocatalytic activities of graphitic carbon nitride in hexavalent chromium reduction and rhodamine B degradation under visible light irradiation

    Chuaicham Chitiphon, Sasaki Keiko

    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY   255  2018年03月  [査読有り]

  • Influence of the pre-dispersion of montmorillonite on organic modification and the adsorption of perchlorate and methyl red anions

    Wuhui Luo, Keiko Sasaki, Tsuyoshi Hirajima

    Applied Clay Science   154   1 - 9  2018年03月  [査読有り]

     概要を見る

    In this study, hexadecyl pyridinium chloride (HDPy-Cl) was applied to modify powdery and dispersed montmorillonite (pMt and dMt, respectively). Then, perchlorate (ClO4 −) and methyl red (MR) were selected as representatives of hazardous inorganic and organic pollutants, respectively, to investigate the influence of the dispersion of Mt on their adsorption using the obtained composites (pMt/HDPy and dMt/HDPy). Based on the X-ray diffraction patterns and water chemistry results, pre-dispersion of Mt resulted in a lower crystallinity of the obtained composite with slightly higher contents of HDPy+ (0.93 mmol/g-Mt) and HDPy-Cl (1.41 mmol/g-Mt) compared to the original powdery Mt (0.85 and 1.36 mmol/g-Mt). Moreover, as supported by thermogravimetry results, the amount of HDPy distributed on the external surface of dMt/HDPy was greater than that on pMt/HDPy, which was opposite of the HDPy content in the interlayer space. The adsorption kinetic of ClO4 − and MR on two composites was studied and the results were fitted by three models, where the intra-particle diffusion model fitted the experimental data best. Similar adsorption capacities were obtained, and the slight differences in the adsorption kinetics as supported by the intra-particle diffusion model were ascribed to the differences in the HDPy contents and configuration. The pre-dispersion of Mt is not necessary when a modified composite is planned for use as an adsorbent of pollutants, but it would be beneficial to the synthesis of clay/polymer nanocomposites.

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    16
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  • Suppression mechanism of anionic pollutants released from fly ash by Ca additives

    Shingo Nakama, Quanzhi Tian, Binglin Guo, Niko Pahlevi, Zhaochu Hu, Keiko Sasaki

    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY   255  2018年03月  [査読有り]

  • Calcination effect of borate-bearing hydroxyapatite on the mobility of borate

    Keiko Sasaki, Kenta Toshiyuki, Binglin Guo, Keiko Ideta, Yoshikazu Hayashi, Tsuyoshi Hirajima, Jin Miyawaki

    JOURNAL OF HAZARDOUS MATERIALS   344   90 - 97  2018年02月  [査読有り]

     概要を見る

    Discharge from accidental nuclear power plants includes boric acid, which is used as a neutron absorbent in nuclear reactors. Co-precipitation of borate with hydroxyapatite (HAp), using Ca(OH)(2), is known to be an effectively fast method for stabilization of borate as well as coexisting radioactive nuclides. To reduce bulky volume of solid residues after co-precipitation, calcination is necessary to investigate the chemical stability of targets. Calcination at 850 degrees C resulted in the high crystalization of HAp with formation of chi CaO center dot B2O as a by-phase in which chi increased with a decrease in the borate contents. After calcination, the lattice parameter a of HAp showed a reentrant curve and c showed a convex curve with an increase in borate contents. A dissolution assay revealed that calcination sometimes increases the borate moiety and that the acceptable B contents in HAp are lower than 1.59 mmol/g-calcined HAp. These results imply that during calcination of HAp, some borate is excluded to form the by-phase chi CaO center dot B2O3 which is relatively insoluble in water, but some other fractions might be additionally emitted from the amorphous phase to weakly bind the calcined products. (C) 2017 Elsevier B.V. All rights reserved.

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    7
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  • Floatability of molybdenite and chalcopyrite in artificial seawater

    Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Hajime Miki, Keiko Sasaki

    MINERALS ENGINEERING   115   117 - 130  2018年01月  [査読有り]

     概要を見る

    Seawater has been reported to depress the floatability of molybdenum in copper-molybdenum (Cu-Mo) flotation circuits under alkaline conditions (pH &gt; 9.5). However, the seawater used in the process contains various minerals and flotation reagents, which make it difficult to investigate the depression mechanism. This paper presents a fundamental study into the effect of artificial seawater as a seawater model solution on the floatability of molybdenite and chalcopyrite, which are the main minerals in the Cu-Mo flotation process. Floatability tests in the absence of flotation reagents (Le., frothers and collectors) reveal that artificial seawater adversely affects the floatability of molybdenite and chalcopyrite at pH &gt; 9. This phenomenon can be attributed to the adsorption of hydrophilic Mg(OH)(2) precipitates formed under alkaline conditions on the mineral surfaces, which increases the surface wettability of the mineral particles, as shown by contact angle measurements and atomic force microscopy (AFM) images. The effect of kerosene as a molybdenite collector has also been investigated to assess its potential in the selective flotation of molybdenite and chalcopyrite in artificial seawater.

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  • Synergetic co-immobilization of SeO4 2- and Sr2+ from aqueous solution onto multifunctional graphene oxide and carbon-dot based layered double hydroxide nanocomposites and their mechanistic investigation

    Paulmanickam Koilraj, Yuta Kamura, Keiko Sasaki

    Journal of Materials Chemistry A   6 ( 21 ) 10008 - 10018  2018年  [査読有り]

     概要を見る

    The co-immobilization of radioactive Sr2+ and SeO4 2- using a multifunctional material is an interesting area of research for the total remediation of radioactive wastes. However, it is rather challenging to target both the anion and cation through the realization of a multifunctional ability of the resultant sorbent. In this work, MgAl-NO3-layered double hydroxides (LDHs) containing graphene oxide (GO) and carbon-dot (C-dot) nanocomposites were synthesized and contrasted for the co-immobilization of Sr2+ and SeO4 2-. Zeta potential measurements and TEM observation of the MgAl-NO3-LDH/C-dot composite indicated that the carbon-nanodot was attached to the surface of LDH nanosheets, while in the MgAl-NO3-LDH/GO composites the LDH nanosheets were decorated on the larger sized GO nanosheets. Adsorption studies found that the normalized Sr2+ adsorption capacity was 1.793 mmol g-1 on MgAl-NO3-LDH/GO, which was nine times higher than that for the MgAl-NO3-LDH/C-dot composite and GO. The enhancement in the Sr2+ adsorption capacity is due to the co-operative effect of the LDH and GO. The adsorption of Sr2+ on the MgAl-NO3-LDH/C-dot occurs by co-ordination with the -COO- group, while ligand exchange and ionic interaction with the alkoxide anion are the dominant mechanisms on the MgAl-NO3-LDH/GO composite. Moreover, the adsorption capacity of both Sr2+ and SeO4 2- increased synergistically in the bi-component system containing both ions. The present technique is promising and offers a sustainable and environmentally friendly multifunctional material for the co-immobilization of both anionic and cationic radioactive surrogates from aqueous solutions.

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    21
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  • Solidification of ettringite after uptaking selenate as a surrogate of radionuclide in glass-ceramics by using industrial by-products

    Binglin Guo, Keiko Sasaki, Tsuyoshi Hirajima

    JOURNAL OF MATERIALS SCIENCE   52 ( 22 ) 12999 - 13011  2017年11月  [査読有り]

     概要を見る

    After accumulation of toxic ions from a contaminated source, spent absorbents and coprecipitation sludge should be stabilized before landfilling for long time storage, especially in the case of absorbed radionuclides. Therefore, development of novel and efficient method to stabilize spent absorbents that contain highly toxic ions is urgently needed. In the present work, the use of industrial by-products as raw materials to produce ceramics to treat toxic waste was investigated. As a typical oxoanion absorbent, selenate-doped ettringite was mixed with granulated blast furnace slag and silica fume and then calcined at various temperatures to produce glass-ceramics. Above 800 A degrees C, the amorphous mixture was converted to glass-ceramics, which were subjected to the toxicity characteristic leaching procedure test. The synthesized ceramics exhibited excellent behavior for immobilization of selenate, and only 0.1 mg/L of selenate was leached out. However, the total concentration of selenate in the mixture was not reduced during calcination. The X-ray photoelectron spectroscopy revealed the stabilization mechanism is based on encapsulation. In addition, the ceramic materials exhibited excellent chemical stability at pH 2-12. These results showed that industrial by-products can be successfully applied to produce ceramics for immobilization and storage of hazardous wastes.

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    15
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  • Eco-Friendly Alkali-Free Arginine-Assisted Hydrothermal Synthesis of Different Layered Double Hydroxides and Their Chromate Adsorption/Reduction Efficiency

    Paulmanickam Koilraj, Keiko Sasaki

    CHEMISTRYSELECT   2 ( 32 ) 10459 - 10469  2017年11月  [査読有り]

     概要を見る

    A new one-pot synthesis of highly crystalline MgAl-, CoAl- and ZnAl-layered double hydroxides (LDHs) containing NO3- as interlayer anion along with the surface functionalization of L-arginine was demonstrated by the ecofriendly alkali-free arginine-assisted hydrothermal method to examine the adsorptive reduction of chromate (CrO42-) from aqueous solutions. The amino acid mediated water hydrolysis resulted abundant OH- in the medium, which served as precipitant, and the NO3- from metal precursor acts as an interlayer anion along with surface functionalization of amino acid. Adsorption studies revealed that the removal of CrO42- by anion exchange was the greatest in MgAl-LDH with 1.619mmol-Cr/g of LDH. The mechanism of CrO42- removal was due to the ion-exchange of NO3- from the interlayer as well as the counter anions present on the functionalized arginine cation. The adsorbed CrO42- was partially reduced to nontoxic Cr3+ on the surface of LDH due to the presence of amino acid functionalization. The present technique provides several advantages from the aspect of sustainable chemistry: (i) avoiding hazardous alkali for the preparation of LDH, (ii) removal of CrO42- by ion-exchange and (iii) partial detoxification of CrO42- by reduction to Cr3+ on the surface of the LDH.

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    10
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  • Selenite and selenate uptaken in ettringite: Immobilization mechanisms, coordination chemistry, and insights from structure

    Binglin Guo, Keiko Sasaki, Tsuyoshi Hirajima

    CEMENT AND CONCRETE RESEARCH   100   166 - 175  2017年10月  [査読有り]

     概要を見る

    Although ettringite is a crucial material in terms of Se immobilization, the immobilization mechanisms, atomic configuration, and intercolumn structure of Se sorbed in ettringite are unclear. The immobilization mechanism of Se oxoanions was evaluated through structural insight into ettringite. It is contrasting between SeO32- and SeO42- in chemical property of the solid residues after immobilization. The oxoanion exchange with structural SO42- is the main mechanism for immobilization of SeO42-. In contrast, SeO32- is easily immobilized to form inner-sphere complexes in ettringite. In addition, it is necessary to reveal the SeO32- complexation sites for understanding the mechanisms in immobilization of SeO32-. Based on the characterization results with the bond valence theory, the location sites of sorbed SeO32- in ettringite structure were proposed. The results obtained in this work are relevant to the understanding of Se and its isotopes immobilized in cement or alkaline environments, especially for nuclear waste management.

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  • Carbon-Dot-Decorated Layered Double Hydroxide Nanocomposites as a Multifunctional Environmental Material for Co-immobilization of SeO42- and Sr2+ from Aqueous Solutions

    Paulmanickam Koilraj, Yuta Kamura, Keiko Sasaki

    ACS SUSTAINABLE CHEMISTRY & ENGINEERING   5 ( 10 ) 9053 - 9064  2017年10月  [査読有り]

     概要を見る

    Co-immobilization of cationic and anionic radionuclides is highly desirable for total remediation of radioactive wastewater. Carbonaceous nano materials have received much attention in the field of water remediation and pollution control in recent years. However, the handling of these nano materials is challenging due to increased bioavailability and toxicity. In this work, MgAl-NO3 layered double hydroxide (LDH) was synthesized and modified using carbon nanodots (C-dot). The prepared materials were characterized using powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR), zeta potential, and transmission electron microscopy (TEM) observation. Adsorption of SeO42- and Sr2+ on MgAl-NO3-LDH/C-dot composites showed that the Sr2+ immobilization capacities increased with an increase in the amount of C-dot. The mechanism of Sr2+ adsorption on these composites occurs via coordination with the -COO- group of C-dot, whereas that of SeO42- occurs through ion exchange with NO3- in the interlayer galleries of LDH. The adsorption of Sr2+ and SeO42- was enhanced in both bicomponent (Sr2+ + SeO42-) and tricomponent systems (Sr2+ + SeO42- + M+/M2+ = coexisting cations or A(n-) = coexisting anions) with the presence of other anion and cations. The MgAl-NO3-LDH/C-dot composites demonstrated that the high adsorption efficiency of Sr2+ and SeO42- than most of other materials reported. These results demonstrate that MgAl-NO3-LDH/C-dot composites are an effective adsorbent for total remediation of anionic and cationic radioactive nuclides from wastewater.

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  • Quantitative analysis of radiocesium retention onto birnessite and todorokite

    Qianqian Yu, Toshihiko Ohnuki, Naofumi Kozai, Fuminori Sakamoto, Kazuya Tanaka, Keiko Sasaki

    CHEMICAL GEOLOGY   470   141 - 151  2017年10月  [査読有り]

     概要を見る

    Although the Cs adsorption onto soil minerals has been widely studied, the structural factor of Mn oxides affecting the adsorption behavior of trace amounts of Cs is unclear. In order to elucidate the adsorption mechanisms of radioactive Cs at trace levels and the role of Mn oxides on Cs migration in the terrestrial environment, the Cs adsorption onto birnessite and todorokite was investigated for a wide range of concentrations (1 x 10(-10) mol/L to 0.1 mol/L) and an ion-exchange model was used to interpret the adsorption data. Although birnessite showed a higher Cs adsorption capacity than todorokite, most of the Cs adsorbed onto birnessite was desorbed by ion exchange. Two types of adsorption sites were observed for todorokite. Despite low density, the selectivity coefficient was much higher for the T-1 site (Log(Na) K-Cs(sel) = 4.2) than for the T-2 site (LogNa K-Cs(sel)=-0.6). Sequential extraction was carried out at Cs concentrations of 1 x 10(-9) mol/L and 1 x 10(-3) mol/L. At lower concentrations, approximately 34% of the adsorbed Cs was residual in the todorokite after the sequential extraction; this value was much higher than the results for the Cs-adsorbed birnessite as well as the Cs-adsorbed todorokite at higher concentrations. The present results indicate that the structural factors of Mn oxides significantly affect the retention capacity of radioactive Cs. Aside from phyllosilicate minerals, todorokite also contributes to the fixation of radioactive Cs in soils.

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    19
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  • Synthesis of sucrose-derived porous carbon-doped ZrxLa1-xOOH materials and their superior performance for the simultaneous immobilization of arsenite and fluoride from binary systems

    Subbaiah Muthu Prabhu, Paulmanickam Koilraj, Keiko Sasaki

    CHEMICAL ENGINEERING JOURNAL   325   1 - 13  2017年10月  [査読有り]

     概要を見る

    Amorphous forms of mixed lanthanum-zirconium oxyhydroxide (ZrxLa1-xOOH) composite materials, containing porous sucrose carbon as a dopant (PSC-ZrxLa1-xOOH), were successfully prepared via co-precipitation and characterized by BET surface area analysis, Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) Energy-dispersive X-ray spectroscopy (EDX) and thermogravimetric analysis (TGA). These synthesized materials were utilized for the simultaneous adsorption of AsO33- and F- from a binary mixture solution in batch tests. The ZrxLa1-xOOH and PSC-ZrxLa1-xOOH composite materials showed both fast adsorption rates and high adsorption capacities towards AsO33- and F- in aqueous solution. Most attractively, ZrxLa1-xOOH and PSC-ZrxLa1-xOOH showed better F- adsorption capacity when the pH was lower than 7, better AsO33- removal when the pH was higher than 9 and were superior to previously reported metallic oxide based sorbents. The mechanism can be interpreted based on the HSAB principle, where the bimetallic oxyhydroxides become "soft acids", while L3+ and Zr4+ are categorized as "hard acids". Moreover, the PSC-ZrxLa1-xOOH adsorbent demonstrated high selectivity for AsO33- in the co-existence of other ions in a triple component system. The fast adsorption kinetics and high capacity make the designed PSC-ZrxLa1-xOOH adsorbent a promising advanced material for the removal of AsO33- and F- from water in practical applications. (C) 2017 Elsevier B.V. All rights reserved.

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    27
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  • Characterization of the intermediate in formation of selenate-substituted ettringite

    Binglin Guo, Keiko Sasaki, Tsuyoshi Hirajima

    CEMENT AND CONCRETE RESEARCH   99   30 - 37  2017年09月  [査読有り]

     概要を見る

    Precipitation of SeO42--substituted ettringite is an efficient method to immobilize SeO42- under alkaline conditions. The effect of SO42- on SeO42- immobilization was investigated, because SO42- is one of the major ions in aqueous and soil environments and it is easily incorporated in ettringite. We aimed to systemically elucidate the formation mechanisms of SeO42--substituted ettringite with and without SO42-. When SO42- and SeO42- coexisted, both oxoanions were immediately coprecipitated with ettringite after adding a Ca source. Although SO42- was partially substituted by SeO42- in ettringite, no other phases were formed during the process. Without SO42- SeO42--substituted AFm phase was formed as an intermediate, confirmed by X-ray diffraction peak at d 2.878, as well as by scanning electron microscopy with energy dispersive X-ray spectroscopy and zeta potential measurements. It is clear that the incorporation mechanism of SeO42- in ettringite is dependent on coexisting SO42- in aqueous environments.

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    21
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  • Effects of grinding montmorillonite and illite on their modification by dioctadecyl dimethyl ammonium chloride and adsorption of perchlorate

    Wuhui Luo, Takeru Fukumori, Binglin Guo, Kwadwo Osseo-Asare, Tsuyoshi Hirajima, Keiko Sasaki

    APPLIED CLAY SCIENCE   146   325 - 333  2017年09月  [査読有り]

     概要を見る

    Montmorillonite (Mt) and illite (lit) were ground for different times under wet condition and sequentially subjected to organic modification by dioctadecyl dimethyl ammonium chloride (DDAC). The influence of the grinding time on the obtained products in terms of DDAC loading and ClO4- adsorption were evaluated. Multiple techniques were used to characterize the changes in structure and morphology before and after mechanical or organic modification. Compared with Ilt, Mt showed a stronger resistance to mechanical treatment due to its swelling property. Silicon nuclear magnetic resonance (Si-29 NMR) spectra and X-ray diffraction (XRD) patterns of samples ground for 30 min indicate the disintegration of Ilt and exfoliation of Mt, resulting in increase of ClO4- uptake by 147% for ont and 13% for OMt. Three stages in the grinding Mt can be proposed, including the separation of large particles into small particles, exfoliation of small particles, and disintegration of exfoliated single layers. In contrast, two stages are involved in the grinding Ilt, which are the destruction/exfoliation of large particles and further disintegration of small exfoliated layers.

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  • Characterization and Production of Solid Biofuel from Sugarcane Bagasse by Hydrothermal Carbonization

    Dewi Agustina Iryani, Satoshi Kumagai, Moriyasu Nonaka, Keiko Sasaki, Tsuyoshi Hirajima

    WASTE AND BIOMASS VALORIZATION   8 ( 6 ) 1941 - 1951  2017年09月  [査読有り]

     概要を見る

    Hydrothermal carbonization of sugarcane bagasse using hot-compressed-water was investigated for the treatment of solid material to understand the occurring decomposition reactions. The experiments were performed in 14 ml of batch type reactor in the range of temperatures 200-300 degrees C and reaction times 3-30 min. After separation of solid residues from liquid material, approximately 34-88 wt% of raw material was recovered as solid products. Characterizations show that increased treatment temperature and reaction time causes structural changes of the sugarcane bagasse. When the temperature and reaction time was increased, hemicellulose and cellulose gradually dissolved, leaving a lignin-like acid insoluble residue. The presence of the residue increases the fixed carbon and decreases the volatile matter content of the solid product. Dehydration significantly decreases the oxygen content and slightly decreases the hydrogen content of the treated material. With these changes, the caloric value and of the solid product increases by 1.1-1.9 times that of the raw material. Higher temperature treatment (300 degrees C) produces a material with high caloric value and fixed carbon, with a composition comparable to typical solid fuels such as lignite (or low rank-coal). The hydrothermal carbonization of sugarcane bagasse could be a solution to reduce environmental pollution caused by the combustion of wet stockpiled sugarcane bagasse in the sugar industry. The treated sugarcane bagasse reduces energy loss, smoke and water vapor during the combustion process.

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    25
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  • Novel biomolecule-assisted interlayer anion-controlled layered double hydroxide as an efficient sorbent for arsenate removal

    Paulmanickam Koilraj, Keiko Sasaki, Kannan Srinivasan

    JOURNAL OF MATERIALS CHEMISTRY A   5 ( 28 ) 14783 - 14793  2017年07月  [査読有り]

     概要を見る

    The synthesis of pure nitrate-containing layered double hydroxides (LDHs) via biomolecule-assisted methods is difficult to achieve without producing substantial waste. For the first time, we demonstrated the synthesis of LDHs with a controlled interlayer anion composition using an environmentally friendly L-arginine-assisted hydrothermal method with zero waste disposal. The mechanism of LDH formation was revealed through PXRD, FT-IR, XPS and ion chromatographic (IC) analyses. At low synthesis temperatures (90-110 degrees C), arginine-mediated water decomposition led to OH- and [Arg(+)]-NO3- formation and thus produced pure NO3--containing LDHs. Conversely, at temperatures above 115 degrees C, L-arginine decomposition occurred and produced NH4+ and CO2, which resulted in CO32--bearing LDHs. The FT-IR spectra of the solid residues, which were obtained at lower temperatures, indicated that several amino acids were functionalized on the surface of the LDHs and replaced by CO32-, which was produced at higher temperatures. The sorption of arsenate from an aqueous solution on the resulting LDHs showed maximum sorption capacity values of 1.675 and 1.972 mmol g(-1) for Mg2.3Al-LDH and Mg2Al-LDH synthesised at 100 degrees C, respectively. The arsenate sorption capacity was enhanced by the functionalization of L-arginine compared with conventionally prepared LDHs. The mechanism of arsenate sorption was based on the ion-exchange of interlayer NO3- and functionalized arginine molecules. In summary, the chemical precursor L-arginine (utilized in this study) acts as a multifunctional reagent, including (i) a precipitant for the synthesis of LDH, (ii) an engineer for interlayer anion control, (iii) a functional reagent and (iv) a scavenger for free NO3- that is present in the synthesis medium. The current synthesis method did not utilize a hazardous base during synthesis, and the [Arg(+)]-NO3- byproduct can be used as a chemical source for health/skin care formulations with zero waste disposal, which offers great benefits.

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  • Fabrication of Chitosan-Reinforced ZrxAl1-xOOH Nanocomposites and Their Arsenite and Fluoride Depollution Densities from Single/Binary Systems

    Subbaiah Muthu Prabhu, Keiko Sasaki

    CHEMISTRYSELECT   2 ( 22 ) 6375 - 6387  2017年07月  [査読有り]

     概要を見る

    The unique and versatile adsorbents zirconium oxyhydroxide (ZrOOH), aluminum oxyhydroxide (AlOOH), zirconium-aluminum oxyhydroxide (ZrxAl1-xOOH) and chitosan-supported zirconium-aluminum oxyhydroxide (CS@ZrxAl1-xOOH) were synthesized via a simple co-precipitation method. CS was used as a pillar-like support to reinforce the ZrxAl1-xOOH, the resulting material was capable of simultaneously adsorbing both F- and AsO33- because the functional groups of CS facilitated the formation of both ZrOOH and AlOOH nanoparticles. Interestingly, ZrxAl1-xOOH and CS@ ZrxAl1-xOOH had better F- adsorption capacities at pH&lt;7, whereas better AsO33- removal was observed at pH&gt;9. The Langmuir maximum adsorption capacity of CS@ZrxAl1-xOOH was 0.655 and 0.983mmol g(-1) for AsO33- and F-, respectively and the performance was superior to that of previously reported metallic oxide and chitosan-based sorbents. In addition, the presence of coexisting anions revealed that the CS@ZrxAl1-xOOH material selectively removed AsO33- over F- in a binary batch system. The adsorption kinetics of the adsorbents were well fit to the pseudo-second-order model. Due to the simultaneous and quick uptake capacity and cost-effectiveness, CS@ZrxAl1-xOOH nanocomposite have potential application in environmental cleanup.

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  • Selective removal of phosphate using La-porous carbon composites from aqueous solutions: Batch and column studies

    Paulmanickam Koilraj, Keiko Sasaki

    CHEMICAL ENGINEERING JOURNAL   317   1059 - 1068  2017年06月  [査読有り]

     概要を見る

    Porous carbon composites containing varying La contents were synthesized and studied for the sorption of phosphate. The phosphate sorption capacities increased with increasing La content and showed an almost complete La consumption efficiency (P/La molar ratio of 0.936) for the composite containing a La(OH)(3)/porous carbon mass ratio of 0.1 (La-0.1-PC). Phosphate sorption by these composite materials occurred through precipitation of LaPO4 supported by PXRD, XPS and EDS analyses. Kinetic studies revealed that phosphate sorption by the La-0.1-PC composite was rapid and reached equilibrium within 1 h compared to the composites containing higher mass ratio of La(OH)(3). The sorption capacity of phosphate was not reduced in the presence 20 mM chloride and 20 mM sulfate, but was disturbed by 20 mM carbonate. The phosphate sorption in the presence of 25 mg/L humic acid was maintained along with the adsorption of dissolved humic acid by electrostatic adsorption onto the carbon support. Interestingly, the phosphate sorption capacity in seawater was twice that in fresh water, likely because the Ca2+ and Mg2+ ions in seawater enhanced the precipitation of phosphate on the surface of La in the La-PC composite. Column experiments verified that the La-0.1-PC composite was effective for the continuous treatment of phosphate. The current outcome suggests that the La-PC composite can be used as a multifunctional sorbent for the remediation of phosphate along with alkaline metal ions (Ca2+ and Mg2+) as well as the removal of humic substances in wastewaters. Moreover, the spent sorbent could be repurposed as a phosphate plant fertilizer, where it would reduce the cost of disposal and increase the commercial value. (C) 2017 Elsevier B.V. All rights reserved.

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  • Experimental study on freeze drying of Loy Yang lignite and inhibiting water re-adsorption of dried lignite

    Xiangchun Liu, Tsuyoshi Hirajima, Moriyasu Nonaka, Keiko Sasaki

    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS   520   146 - 153  2017年05月  [査読有り]

     概要を見る

    Loy Yang lignite with a high water content was dewatered by freeze drying (FD). The drying kinetics of FD was calculated using thin-layer drying models given in the literature. Residual water content, re adsorption or desorption behaviors, and pore size distributions of all of the samples were investigated. Furthermore, coating with different amounts of kerosene by direct mixing or adsorption methods to restrain water re-adsorption was also investigated. The results showed that FD dewatering contained three steps: a fast dewatering period (-2 h), followed by a reduced drying-rate period (2-3 h) and an apparently falling-rate period (&gt;3 h). The Midilli-Kucuk model described the drying process perfectly and could be employed to predict residual water content in the sample at any time during the FD dewatering process. The moisture holding capacity (MHC) of the FD-treated samples was lower than that of raw lignite, which is because of the effect of the water-lignite bond strength and the diffusion adsorption or desorption force. Moreover, adding kerosene by either adsorption or direct-mixing methods can both decrease MHC because kerosene is coated on the surface and in the pores of the lignite. These prevent water re-adsorption. The adsorption method is better than the direct-mixing method because it consumes less kerosene. (C) 2017 Elsevier B.V. All rights reserved.

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    20
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  • Selective adsorption of inorganic anions on unwashed and washed hexadecyl pyridinium-modified montmorillonite

    Wuhui Luo, Tsuyoshi Hirajima, Keiko Sasaki

    SEPARATION AND PURIFICATION TECHNOLOGY   176   120 - 125  2017年04月  [査読有り]

     概要を見る

    Fourteen anions were selected to investigate their adsorption capacities and affinities to unwashed and washed hexadecyl pyridinium (HDPy)-modified montmorillonite (HDPy/Mt). Correlations between adsorption characteristics and anionic properties including radius and hydration energy were determined. With the exception of IO3-, H2AsO4-, and CrO42-, monovalent anions showed higher adsorption capacities and affinities to unwashed or washed HDPy/Mt than divalent anions, because the latter possess higher hydration energies. Unwashed HDPy/Mt demonstrated higher selectivity toward poorly hydrated monovalent anions because it presented a more hydrophobic environment, whereas strongly hydrated divalent anions more readily intercalate into the less hydrophobic washed HDPy/Mt. Hydration of the counter ion (Cl-) is the driving force for anion adsorption on HDPy/Mt. Higher energy consumption required to dehydrate divalent anions accounts for their lower affinity. Selectivity of HDPy/Mt to anions depends not only on anion size in different phases (from r(1) in aqueous solution to r(2) in the organic solvent-like HDPy/Mt), but also the dielectric constant of HDPy/Mt (epsilon(2)) after HDPy release. (C) 2016 Elsevier B.V. All rights reserved.

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  • Enhancement of fluoride immobilization in apatite by Al3+ additives

    Keiko Sasaki, Shugo Nagato, Keiko Ideta, Jin Miyawaki, Tsuyoshi Hirajima

    CHEMICAL ENGINEERING JOURNAL   311   284 - 292  2017年03月  [査読有り]

     概要を見る

    Immobilization of fluoride (F-) in apatite using Ca(OH)(2) as a mineralizer in the presence of phosphate is known to be accompanied by a stagnation period. This is caused by the formation of hydroxyapatite and/or fluoroapatite (HAp/FAp) on the surface of Ca(OH)(2), which inhibits the dissolution of Ca(OH)(2). Al3+ additives effectively eliminated the delay period, leading to the rapid formation of apatites by suppressing the formation of CaCO3. Zeta potential measurements clearly showed that increasing the quantity of Al3+ additives caused not only a decrease in the initial surface charge but also a decrease in the rate of the surface charge of the solid residues during the reaction, indicating that Al3+ additives enhanced the formation of HAp/FAp. 27Al-nuclear magnetic resonance (NMR) studies of the solid residues indicated that the predominant coordination number of Al was always hexagonal ([6]Al) and that the fraction of [6]AI increased with an increase in the molar ratio of F/Al in the solid residues, suggesting that the stable AlF63- complex was easily incorporated into the apatites. In addition, transmission electron microscope- energy dispersive X-ray spectroscopy (TEM-EDX) revealed a uniform distribution of Al in the apatites, which suggests that in the initial stages of the reaction, free Al3+ ions contribute to the formation of apatite crystal seeds independent of Ca(OH)(2) particles, resulting in the efficient growth of apatites containing F-. This result is helpful for the treatment of F--bearing industrial wastewaters in practical applications by using an Al-bearing Ca source, such as ground-granulated blast-furnace slag. (C) 2016 Elsevier B.V. All rights reserved.

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  • Bioscorodite crystallization using Acidianus brierleyi: Effects caused by Cu(II) present in As(III)-bearing copper refinery wastewaters

    Naoko Okibe, Shiori Morishita, Masahito Tanaka, Keiko Sasaki, Tsuyoshi Hirajima, Kazuhiro Hatano, Atsuko Ohata

    Hydrometallurgy   168   121 - 126  2017年03月  [査読有り]

     概要を見る

    © 2016 Elsevier B.V. This study investigated the effect caused by Cu(II) in synthetic As(III)-bearing copper refinery wastewaters, on microbial scorodite (FeAsO4·2H2O) formation using the thermo-acidophilic Fe(II)- and As(III)-oxidizing archaeon, Acidianus brierleyi. Microbial Fe(II) oxidation and cell growth became only marginal in the presence of 8–16 mM Cu(II), with its As(III) oxidation ability being severely inhibited. Consequently, scorodite formation was disabled by Cu(II) addition. However, feeding scorodite seed crystals readily alleviated Fe(II)- and As(III)-oxidation ability of Ac. brierleyi at 8 mM Cu(II), forming crystalline scorodite within 24 days in shake flasks. Zeta potential analysis indicated cell attachment to the scorodite seed crystal surface, implying its role in providing the immediate support for microbial colonization and enabling more robust microbial reactions. Most of Cu(II) was neither adsorbed nor co-precipitated and remained in the solution phase during scorodite crystallization, with or without the presence of seed crystals. Addition of seed crystals at 0.015, 0.03, 0.075 and 0.15% resulted in As immobilization of 96, 97, 97 and 98%, respectively, by day 24. This study demonstrated that despite of its inhibitory effect on Ac. brierleyi cells, scorodite can still be crystallized in the presence of Cu(II) by feeding scorodite seeds from synthetic copper refinery As(III)-bearing wastewaters.

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  • Bio-modification of carbonaceous matter in gold ores: Model experiments using powdered activated carbon and cell-free spent medium of Phanerochaete chrysosporium

    Kojo T. Konadu, Keiko Sasaki, Takashi Kaneta, Grace Ofori-Sarpong, Kwadwo Osseo-Asare

    HYDROMETALLURGY   168   76 - 83  2017年03月  [査読有り]

     概要を見る

    Carbonaceous matter in refractory gold ore is known to be one of the primary causes of gold recovery loss. Model experiments were conducted to simulate the bio-modification of carbonaceous matter using powdered activated carbon (PAC) as a surrogate and cell-free spent medium (CFSM) of Phanerochaete chrysosporium. The CFSM was used because of the lignin peroxidase and manganese peroxidase secreted by the microbe during its incubation. In the present work, an investigation was conducted to determine the physical and chemical alterations in PAC after enzymatic treatment and its effect on Au(CN)(2)(-) uptake. Characterization of the solid residues of PAC by C-13 NMR and N-2 adsorption after bio-modification revealed that the treatment had decomposed poly-aromatic carbons into aliphatic carbons and also reduced the specific surface area from 1430 m(2)/g to 697 m(2)/g in 14 days. As a result, Au(CN)(2)(-) uptake decreased from 100% (0.048 mmol/g) to 43% within 12 h primarily due to the enzyme treatment and adsorption of CFSM components. It further decreased to 26% due to surface passivation by bio-chemicals derived from CFSM and/or decomposed aliphatic hydrocarbons from aromatic carbons between 7 days and 14 days. These findings may contribute to efforts to decrease preg-robbing in hydrometallurgical processing of refractory gold ores. (C) 2016 Elsevier B.V. All rights reserved.

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  • Synergistic effect of Sr2+ and ReO4- adsorption on hexadecyl pyridinium-modified montmorillonite

    Wuhui Luo, Akihiro Inoue, Tsuyoshi Hirajima, Keiko Sasaki

    APPLIED SURFACE SCIENCE   394   431 - 439  2017年02月  [査読有り]

     概要を見る

    Simultaneous adsorption of Sr2+ and ReO4-, which are surrogates of Sr-90(2+) and (TcO4-)-Tc-99m, on hexadecyl pyridinium (HDPy+)-modified montmorillonite (HDPy/Mt) was investigated. When the amount of HDPy+ corresponding to 0.92 times the cation exchange capacity (CEC) of Mt was added, the obtained composite (HDPy/Mt-0.92) showed considerable adsorption capacities for Sr2+ and ReO4-. Some HDPy+ desorbed from the Mt layer in the presence of ReO4-, providing negatively charged sites on the Mt surface for Sr2+ adsorption. The desorbed HDPy+ interacted with ReO4- and was trapped in the composite in the form of HDPy-ReO4, resulting in adsorption of ReO4-. At high initial concentrations of ReO4-, the HDPy configuration changed after adsorption because of the desorption-adsorption process, which was supported by X-ray diffraction. Based on the results of X-ray photoelectron spectroscopy, in the binary system (i.e., Sr2+ and ReO4-), Sr2+ uptake occurred in the interlayer space, while adsorption of ReO4- occurred on the external surface and probably in the interlayer space. Desorption-adsorption and ion exchange account for Sr2+ uptake, while adsorption of ReO4- was mainly attributed to desorption-adsorption. Compared with the one-adsorbate system, a synergistic effect of simultaneous adsorption of Sr2+ and ReO4- was found in the two-adsorbate system. (C) 2016 Elsevier B.V. All rights reserved.

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  • Synthesis of layered double hydroxide/different carbon material and 90Sr2+ composites for simultaneous adsorption of 79SeO42-

    Yuta Kamura, Paulmanickam Koilraj, Tsuyoshi Hirajima, Keiko Sasaki

    14th International Symposium on East Asian Resources Recycling Technology, EARTH 2017    2017年

     概要を見る

    After the Fukushima Daiichi Nuclear Power Plant accident, a variety of radionuclides has been treated by Advanced Liquid Processing System including different adsorbents. This work aims to synthesize layered double hydroxide (LDH)/different carbon materials composites for simultaneous adsorption of radioactive anion and cation, where 79SeO42- and 90Sr2+ have been selected as targets for removal. As carbon materials, carbon-dot and graphene oxide (GO) were synthesized to modify LDH, in which the presence of carboxylic groups was confirmed by FTIR. TEM observation revealed the sizes of C-dot and LDH particles are 3-5 nm and around 100 nm, respectively, while the size of GO has been reported 1-2 mm. Simultaneous adsorption of SeO42- and Sr2+ was achieved in both composites using surrogates, though ion-exchange of SeO42- with NO 3- in LDH and complexation of Sr2+ with carboxyl group in carbon materials. Comparable adsorption capacities of SeO42- was observed on both composites. However, Sr2+ adsorption capacities were much larger in LDH/GO than LDH/C-dot in any cases of different carbon contents. In addition, Sr2+ adsorption capacities in mmol/g-GO were much larger in LDH/GO composites than pure GO. Zeta potential of LDH/GO was +31.0 mV closer to LDH, while that of LDH-C-dot was -16.4 mV closer to C-dot. These observation suggests there is a clear contrast between two composites. That is, the composite of LDH/GO consists of coverage of larger sheets of GO with smaller sheets of LDH, while the composite of LDH/C-dot consists of coverage of larger sheets of LDH with nano-sized C-dot. Accordingly it is promising to customize the ratio of LDH/GO in the composite considering the different radioactive waste water compositions to treat in various stages.

  • Effect of hydrogen peroxide on separation of chalcopyrite and molybdenite using flotation

    Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Hajime Miki, Keiko Sasaki

    14th International Symposium on East Asian Resources Recycling Technology, EARTH 2017    2017年

     概要を見る

    Various oxidation treatments (i.e., plasma, and ozone) have been applied to separate molybdenite from other sulfide metals. However, plasma and ozone treatments exhibit stronger oxidation on chalcopyrite and molybdenite, reducing the separation selectivity of both minerals in flotation tests. On the other hand, hydrogen peroxide (H2O2) is frequently used as an oxidizing agent in wastewater treatment. It has also been reported to reduce the recovery of sulfide minerals. Therefore, the effect of H2O2 on separation of chalcopyrite and molybdenite was investigated in this study. Contact angle readings and surface images using atomic force microscopy (AFM) showed that chalcopyrite surface was more sensitive to surface oxidation compared to that of molybdenite in H2O2 aqueous solution. The floatability test of single mineral confirmed the contact angle results and AFM images, indicating a possibility for selective separation of chalcopyrite and molybdenite using a H2O2 aqueous solution. In addition, iron was used to improve the oxidation performance of H2O2 and its effect on the selective flotation of chalcopyrite and molybdenite is intensively studied in this work.

  • Image Processing System for Air Classification Using Linear Discriminant Analysis

    Atsunori Tayaoka, Eriko Tayaoka, Tsuyoshi Hirajima, Keiko Sasaki

    Computational Water, Energy, and Environmental Engineering   06 ( 02 ) 192 - 204  2017年

    DOI

  • Enzymatic pre-treatment of carbonaceous matter in preg-robbing gold ores: Effect of ferrous ion additives

    Kojo T. Konadu, Keiko Sasaki, Kwadwo Osseo-Asare, Takashi Kaneta

    Solid State Phenomena   262   43 - 47  2017年  [査読有り]

     概要を見る

    The bio-treatment of double refractory gold ores (DRGO) to reduce preg-robbing needs to account for the heterogeneity of the ore so as to acquire a much more complete picture of the system. To this end, the effects of ferrous ion additives on the degradation of powdered activated carbon (PAC) by cell-free spent medium (CFSM) was studied. Au(CN)2- adsorption and Raman spectrometric results suggest that the ferrous salt could have possibly reacted with some biogenic hydrogen peroxide to aid in the degradation of PAC. The bio-treatment produced mixed solid residues containing some partially degraded aromatic compounds which were soluble in alkaline solutions. Ultimately, biodegradation of PAC using CFSM in the presence of 50 µM FeSO4.7H2 O for 7 days followed by washing with 3 mM NaOH reduced Au(CN)2- uptake by 80%.

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  • Selective flotation of chalcopyrite and molybdenite with H2O2 oxidation

    Tsuyoshi Hirajima, Hajime Miki, Gde Pandhe Wisnu Suyantara, Hidekazu Matsuoka, Ahmed Mohamed Elmandy, Keiko Sasaki, Yuji Imaizumi, Shigeto Kuroiwa

    MINERALS ENGINEERING   100   83 - 92  2017年01月  [査読有り]

     概要を見る

    The selective flotation of chalcopyrite (CuFeS2) and molybdenite (MoS2) was studied using surface oxidation treatments (i.e., ozone (O-3) and hydrogen peroxide (H2O2)). The results indicated that the oxidation treatments had different effects on the wettability of chalcopyrite and molybdenite. Single mineral flotation results showed that the H2O2 treatment had higher separation selectivity for molybdenite and chalcopyrite compared with that of the ozone treatment. The contact angle measurement and X-ray photoelectron spectroscopy (XPS) analysis results showed that the chalcopyrite surface became hydrophilic owing to the surface deposition of oxidized iron and copper after the H2O2 treatment. On the other hand, the contact angle of molybdenite slightly increased following the H2O2 treatment at high concentrations. Possible mechanisms of this phenomenon were proposed in this work. Moreover, the separation selectivity of each oxidation method was discussed. Flotation tests using bulk Cu-Mo concentrate showed that H2O2 could deliver a flotation result comparable to conventional Cu-Mo flotation using NaHS. (C) 2016 Elsevier Ltd. All rights reserved.

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  • Solidification of selenate-bearing ettringite in glass-ceramics by using industrial by-products

    Binglin Guo, Keiko Sasaki, Tsuyoshi Hirajima

    14th International Symposium on East Asian Resources Recycling Technology, EARTH 2017    2017年  [査読有り]

     概要を見る

    ©The Mining and Materials Processing Institute of Japan After accumulation of radionuclides from contaminated sources, spent absorbents and co-precipitated sludge is classified into radioactive wastes and should be stabilized before landfilling for long term storage. Therefore, development of efficient technologies to stabilize spent absorbents bearing radionuclides is urgently needed. In the present work, the ultilization of industrial by-products as raw materials to produce ceramics to stabilize radioactive waste was investigated using a surrogate. Selenate-doped ettringite was mixed with granulated blast furnace slag (GBFS) and silica fume (SF) and then calcined at various temperatures to produce glass-ceramics. Above 800 °C, the amorphous mixture was converted to glass-ceramics, which were subjected to the toxicity characteristic leaching procedure (TCLP) test. The synthesized ceramics exhibited excellent results for immobilization of selenate in which less than 0.1 mg/L of selenate was leached out. Moreover, according to the digestion experiment, the quantity loss of selenate in the ceramics was not observed even after calcination. The X-ray photoelectron spectroscopy (XPS) revealed the stabilization mechanism is based on encapsulation. In addition, the ceramic materials exhibited excellent chemical stability in a wide range of pH from 2 to 12. These results showed that industrial by-products can be successfully applied to produce ceramics for not only immobilization but also storage of hazardous wastes.

  • Mechanism of silver-catalyzed bioleaching of enargite concentrate

    Keishi Oyama, Tsuyoshi Hirajima, Keiko Sasaki, Hajime Miki, Naoko Okibe

    Solid State Phenomena   262 SSP   273 - 276  2017年  [査読有り]

     概要を見る

    © 2017 Trans Tech Publications, Switzerland. Silver-catalyzed bioleaching of enargite concentrate with three bacteria (Acidimicrobium ferrooxidans ICP, Sulfobacillus sibiricus N1, Acidithiobacillus caldus KU) and one archaeon (Ferroplasma acidiphilum Y) was conducted in order to elucidate the catalytic mechanism of silver sulfide in enargite bioleaching. Whereas Cu recovery remained relatively low (43%) and Fe dissolved completely without silver sulfide, Cu recovery was greatly enhanced (96%) and Fe dissolution was suppressed (29%) in the presence of 0.04% silver sulfide. In the latter case, 52% of the solubilized As was re-immobilized, in contrast to only 14% As re-immobilization in the former. The silver-catalyzed bioleaching (at 0.04% silver sulfide) proceeded at low redox potentials within the optimal range, which likely promoted enargite dissolution via formation of intermediate Cu2 S. XAFS analysis revealed that As was mainly immobilized as As(V), which was in agreement with the EPMA results detecting ferric arsenate passivation on some enargite grains. Furthermore, formation of trisilver arsenic sulfide (Ag3 AsS4) was detected by XRD and EPMA, covering the surface of enargite particles. An intermediate layer, consisting of (Cu,Ag)3 AsS4, was also observed between the enargite grain and trisilver arsenic sulfide layer, implying that Cu in enargite may be gradually substituted by solubilized Ag. Kinetic study suggested that these secondary minerals do not rate-limit the enargite dissolution. The overall mechanism of silver-catalyzed bioleaching of enargite concentrate will be proposed.

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  • Microbiological as(III) oxidation and immobilization as scorodite at moderate temperatures

    Yuta Era, Tsuyoshi Hirajima, Keiko Sasaki, Naoko Okibe

    Solid State Phenomena   262 SSP   664 - 667  2017年  [査読有り]

     概要を見る

    © 2017 Trans Tech Publications, Switzerland. The potential utility of mesophilic/moderately thermophilic acidophiles was investigated for immobilization of arsenic (As) as scorodite (FeAsO4·2H2O) at moderate temperatures (35–45˚C). Here, the acid-tolerant mesophile Thiomonas cuprina Hö5 and acidophilic moderately thermophile Acidimicrobium ferrooxidans ICP were selected as As(III)- and Fe(II)- oxidizers, respectively. Due to a difference in their optimal growth pHs, a 2-step reaction consisting of the 1st As(III) oxidation step followed by the Fe(II) oxidation + precipitation step was studied. In our previous study, the optimal [Fe(II)]ini/[As(III)]ini molar ratio for bioscorodite formation at 70˚C (at [As(III)]ini = 1000 ppm) was shown to be around 1.4. However, setting the same molar ratio at moderate temperatures (35-45˚C) resulted in formation of unstable amorphous ferric arsenate. Lowering the ratio to ≤ 1.0 led to precipitation of crystalline bioscorodite with > 90% As(III) removal at 45˚C.

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  • Optimization of bioscorodite crystallization for treatment of as(III)-bearing wastewaters

    Masahito Tanaka, Tsuyoshi Hirajima, Keiko Sasaki, Naoko Okibe

    Solid State Phenomena   262 SSP   555 - 558  2017年  [査読有り]

     概要を見る

    © 2017 Trans Tech Publications, Switzerland. Arsenic (As) is a major impurity contaminating metal refinery wastewaters. To immobilize As ions, we have previously reported microbial scorodite (FeAsO4·2H2O) crystallization using the thermo-acidophilic iron-oxidizing archaeon, Acidianus brierleyi. In order to extend the applicable range of As(III)-bearing metal refinery wastewaters (especially for dilute As(III) concentrations of 250–1500 ppm), this study investigated the effect of several factors possibly affecting the bioscorodite crystallization efficiency; (i) [Fe(II)]ini/[As(III)]inimolar ratio at different target As(III) concentrations, (ii) initial pH, and (iii) seed scorodite with different morphologies. The [Fe(II)]ini/[As(III)]inimolar ratio strongly affected the bioscorodite crystallization efficiency at each target As(III) concentration. Whilst the [Fe(II)]ini/[As(III)]inimolar ratio of 1.4 was most effective at 500–1500 ppm As(III), the optimal molar ratios for treating more dilute concentrations (&lt; 500 ppm) were shown to be relatively higher. However, further increasing the [Fe(II)]ini/[As(III)]inimolar ratio resulted in formation of unwanted potassium jarosite (KFe3(OH)6(SO4)2) together with scorodite. Lowering the initial pH from 1.5 to 1.2 resulted in earlier scorodite nucleation, but lower overall As immobilization. Feeding chemical- and bio-scorodite seed crystals differently affected the reaction speed and the stability of newly-precipitated bioscorodite. The TCLP test indicated that scorodite formed on bioscorodite seeds is more stable than that formed on chemically-synthesized scorodite seeds.

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  • Electrolysis Oxidation of Chalcopyrite and Molybdenite for Selective Flotation

    Hajime Miki, Hidekazu Matsuoka, Tsuyoshi Hirajima, Gde Pandhe, Wisnu Suyantara, Keiko Sasaki

    MATERIALS TRANSACTIONS   58 ( 5 ) 761 - 767  2017年  [査読有り]

     概要を見る

    Electrolysis oxidation of chalcopyrite and molybdenite was investigated, via various electrochemical methods, with the aim of realizing selective flotation of these minerals. Result of potential polarization indicated that oxidation via electrolysis affected only the chalcopyrite surface, owing mainly to the difference in conductivity of these minerals. Also measurements of contact angle after electrolysis indicated that contact angle of chalcopyrite selectively decreased whereas that of molybdenite did not decrease drastically. XPS analyses after electrolysis indicated that chalcopyrite peak decreased whereas iron oxyhydroxide (goethite) and iron sulfate increased, it suggests that these oxidation products covered on the surface of chalcopyrite. On the other hand, molybdenite peak is similar after electrolysis except for molybdenum oxide/oxygen with molybdenite can be seen for oxygen peak. From these results and general knowledge that sulfide hydrophobicity and sulfate/oxyhydroxide hydrophilicity, it can be explained that with electrolysis oxidation, hydrophilic oxihydroxide and sulfate covered on the surface of hydrophobic chalcopyrite then chalcopyrite surface became hydrophilic. On the other hand, molybdenite surface keep hydrophobic since its difficulty of oxidation and it is difficult to stay molybdenum oxide on the surface due to its soluble property. These results revealed that chalcopyrite was selectively oxidized and, hence, selective flotation of chalcopyrite and molybdenite was possible. This electrolysis oxidation methods were compared with those governing other oxidation treatments.

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  • Structural transformation of selenate ettringite: a hint for exfoliation chemistry

    Binglin Guo, Keiko Sasaki, Tsuyoshi Hirajima

    RSC ADVANCES   7 ( 67 ) 42407 - 42415  2017年  [査読有り]

     概要を見る

    Exfoliation of layeredmaterials has attracted tremendous interest since nanomaterials have become practically applied in many disciplines. In this study, the structural transformation of packed columnar selenate ettringite into nanoscale particles has been investigated. The structural transformation of ettringite has been evidenced based on the results of X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), and extended X-ray adsorption fine structure (EXAFS). The structural transformation is caused by the electrostatic repulsion between guest sulfate ions and selenate. However, the atomic arrangement of columnar parts of selenate ettringite is still maintained. In addition, a similar phenomenon is more noticeably observed when it is soaked in ethanol. This suggests that this columnar material has the potential to be exfoliated into a single nanoscale column by reactions with polar solvents. Finally, a stable colloidal solution formed when selenate ettringite was soaked in butanol. This is because the surface of the columnar parts in ettringite is surrounded by structural water molecules that can interact with OH groups of strongly polar solvent molecules to form hydrogen bonds that can directly exfoliate selenate ettringite and convert to nanoparticles. It is clear that ettringite could be directly exfoliated to nanoparticles in polar organic solvents, which has potential utility for wide applications.

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  • Simultaneous Determination of Manganese Peroxidase and Lignin Peroxidase by Capillary Electrophoresis Enzyme Assays

    Sumire Kudo, Airi Harada, Hiroe Kubota, Keiko Sasaki, Takashi Kaneta

    ACS Omega   2 ( 10 ) 7329 - 7333  2017年  [査読有り]

     概要を見る

    Here, we developed an enzyme assay of manganese peroxidase (MnP) by capillary electrophoresis using an in-capillary reaction and applied it to a simultaneous assay of MnP and lignin peroxidase (LiP). The enzyme activity of MnP was determined from the peak area corresponding to Mn(III)-malonate produced by the plug-plug reaction between MnP and Mn(II) in a separation capillary. A background electrolyte containing 250 mM malonate buffer (pH 4.5) and 5 mM cetyltrimethylammonium bromide was employed for the separation of Mn(III)-malonate from MnP at -10 kV after a plug-plug reaction for 5 min. Although the assay permitted the determination of purified MnP, we found that both LiP and MnP have similar activities against their substrates, that is, LiP catalyzed the oxidation reaction of Mn(II) as well as MnP, whereas MnP catalyzed the oxidation reaction of veratryl alcohol which was the substrate used in the LiP assay developed previously. Thus, we proposed a method to discriminate MnP from LiP based on the difference in the activities of these enzymes to each substrate. Amounts of MnP and LiP in a mixture were successfully evaluated by the proposed method.

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  • Adsorption characteristics of arsenate on colloidal nanosheets of layered double hydroxide

    Paulmanickam Koilraj, Yu Takaki, Keiko Sasaki

    APPLIED CLAY SCIENCE   134   110 - 119  2016年12月  [査読有り]

     概要を見る

    Nanomaterials have gained much interest in water remediation and pollution control in recent years. However, the toxicity associated with nanoparticles remaining in solution after remediation has high impact on the environment. The present study examined the synthesis and characterization of colloidal Mg2Al-NO3 layered double hydroxide (Mg2Al-UD-LDH) nanosheets and their application as adsorbent toward arsenate immobilization. Colloidal LDH nanosheets featured the absence of nanoparticles release in the environment differently from other nanomaterials. The adsorption studies conducted in batch method, revealed that colloidal Mg2Al-UD-LDH nano sheets (obtained by ultrasonic treatment of Mg2Al-NO3-LDH suspension) achieved a higher arsenate adsorption density of 1.21 mmol/g than parent Mg2Al-NO3-LDH (1.16 mmol/g) at a solid-to-solution dosage of 0.78 g LDH/L. The adsorption mechanism of arsenate onto colloidal Mg2Al-UD-LDH nanosheets proceeded through restacking of the nanosheets, besides ion-exchange onto Mg2Al-NO3-LDH and surface adsorption onto Mg2Al-CO3-LDH. Kinetics of arsenate adsorption onto colloidal Mg2Al-UD-LDH nanosheets was rapid, reaching equilibrium within 5 min, whereas equilibrium was reached within 120 min in the presence of Mg2Al-NO3-LDH. The colloidal LDH nanosheets stacking effect was restricted at higher LDH/As ratios owing to electrostatic repulsion among the nanosheets, as determined by zeta potential measurements. Semi-pilot scale static model systems for arsenate adsorption were examined to further investigate the adsorption performance of colloidal Mg2Al-UD-LDH nanosheets in natural water systems such as river, pond, or lake. Arsenate adsorption was rapid onto colloidal Mg2Al-UD-LDH nanosheets owing to their high dispersibility; specifically, 100% adsorption efficiency was achieved within 5 min. Thus, the high adsorption capacity, dispersibility, and fast kinetics of arsenate removal onto colloidal Mg2Al-UD-LDH nanosheets promising for use as an efficient adsorbent for water remediation. (C) 2016 Elsevier B.V. All rights reserved.

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  • The Development of Fine Microgram Powder Electrode System and Its Application in the Analysis of Chalcopyrite Leaching Behavior

    Hajime Miki, Tsuyoshi Hirajima, Kazunori Oka, Keiko Sasaki

    MINERALS   6 ( 4 )  2016年12月  [査読有り]

     概要を見る

    An electrode system to study the mechanism of fine microgram powder sulfide mineral dissolution was developed by using a relatively simple method that enables the attachment of micrograms of fine powder to a platinum plate surface. This system yields highly reproducible results and is sensitive compared with conventional electrode systems for various sulfide minerals such as pyrite, chalcopyrite, chalcocite, enargite, and tennantite. The leaching behavior of chalcopyrite was re-examined in a test of the application of this electrode system. Chalcopyrite dissolution is enhanced in specific potential regions because it is believed to be reduced to leachable chalcocite, but this result is inconclusive because it is difficult to detect the intermediate chalcocite. Powder chalcopyrite in the new powder electrode system was held at 0.45 V in the presence of copper ion and sulfuric acid media followed by an application of potential in the anodic direction. Besides the chalcopyrite oxidation peak, a small peak resulted at similar to 0.55 V; this peak corresponds to reduced chalcocite, because it occurs at the same potential as the chalcocite oxidation peak.

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  • Effects of hydrothermal treatment coupled with mechanical expression on combustion performance of Loy Yang lignite

    Xiangchun Liu, Tsuyoshi Hirajima, Moriyasu Nonaka, Keiko Sasaki

    JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY   126 ( 3 ) 1925 - 1935  2016年12月  [査読有り]

     概要を見る

    The combustion characteristics and kinetics of hydrothermal treatment (HT) without addition of extra water and of HT coupled with mechanical expression (HT-ME) were investigated using thermogravimetric analysis at various heating rates. The relationships between various physicochemical properties, i.e., amounts of volatile matter and fixed carbon, specific surface area, and pore volume, and combustion performance were also investigated. The activation energy was calculated using the Kissinger-Akahira-Sunose isoconversional method. The results showed that for samples treated using HT and HT-ME, the ignition temperatures and temperatures at which the mass loss rates were at maximum, mainly because of char combustion, were significantly higher than those for raw lignite. They increased slightly with increasing processing temperature, suggesting that HT and HT-ME decrease the reactivity of Loy Yang lignite. The maximum combustion rates of the treated samples were higher than those of raw lignite and the values for the HT and HT-ME samples differed slightly from each other. The higher maximum combustion rates indicate that HT and HT-ME modify the combustion intensity of Loy Yang lignite. Furthermore, the combustion of raw lignite can be described by multistep kinetics, whereas single rate-limiting step kinetics can be used to describe the kinetics of the other samples. Average activation energies of samples treated using HT and HT-ME at 200 degrees C reached the maximum values.

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  • Removal mechanism of arsenate by bimetallic and trimetallic hydrocalumites depending on arsenate concentration

    Yu Takaki, Xinhong Qiu, Tsuyoshi Hirajima, Keiko Sasaki

    APPLIED CLAY SCIENCE   134   26 - 33  2016年12月  [査読有り]

     概要を見る

    We investigated the influence of initial arsenate concentration (C-0) in the 5th order of magnitude on removal of arsenate by hydrocalumite (bimetallic layered double hydroxide, LDH) and Mg-doped hydrocalumite (trimetallic LDH) from aqueous solution. These hydrocalumites were prepared by the microwave-assisted hydro thermal treatment. There is a trend that the larger adsorption density of arsenate (Q(e)) values is observed with bimetallic LDH under low C-0 values and with trimetallic LDH under high C-0 values. The transitional C-0 values ranged at 2.10-2.96 mM. Comprehensively understanding characterization results for the solid residues after adsorption of arsenate by X-ray diffraction, Al-27-nuclear magnetic resonance, and scanning electron microscopy energy dispersive X-ray, the mechanism to remove arsenate was dependent on arsenate concentrations. At low arsenate concentration, partial intercalation and dissolution-reprecipitation (DR) happened together. With increasing C-0, full intercalation and DR happened to bring out one phase of arsenate-bearing hydrocalumite. Under the very high C-0, DR mechanism happened at the edge sites of LDH sheets, leading that the newly formed massive precipitates block the further intercalation with nitrate. As a result, two phases of LDH were observed. The greater Q(e) with bimetallic LDH in low concentration comes from high crystallinity to enhance partial ion-exchange, and greater Q(e) with trimetallic LDH in high concentration is derived from more fragile properties to enhance DR mechanism. (C) 2016 Elsevier B.V. All rights reserved.

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  • Encapsulation of a powdery spinel-type Li+ ion sieve derived from biogenic manganese oxide in alginate beads

    Paulmanickam Koilraj, Siwaporn Meejoo Smith, Qianqian Yu, Sarah Ulrich, Keiko Sasaki

    POWDER TECHNOLOGY   301   1201 - 1207  2016年11月  [査読有り]

     概要を見る

    A powdery lithium ion sieve (HMO) derived from biogenic birnessite was homogeneously integrated in sodium alginate (AL) beads. The composite beads were then characterized and their Li+ adsorption properties were investigated. Scanning electron microscopy-energy dispersive spectroscopy analysis showed that the HMO particles were homogeneously dispersed in the AL beads even after drying. The adsorption isotherm of Li+ adsorption to HMO encapsulated in AL beads (HMO-AL) was well fitted by the linear Langmuir model, and the beads showed a maximum adsorption capacity of 3.61 mmol/g based on HMO, which is comparable with the value of the original powdery HMO. Kinetic studies revealed that adsorption of Li+ follows a pseudo-second-order model with rate constant k(2) = 2.8-11.9 x 10(-3) g/(mmol min) for the initial Li+ concentration range 2.56-4.23 mM. Diffusion of Li+ from aqueous solution to the HMO particle through the Ca-AL network is the rate-limiting step for Li+ adsorption to HMO-AL beads. The HMO-AL beads enhanced the handling efficiency for Li+ adsorption and reused without significant reduction of Li+ adsorption efficacy. (C) 2016 Elsevier B.V. All rights reserved.

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  • Effect of freeze drying on characteristics of Mg-Al layered double hydroxides and bimetallic oxide synthesis and implications for fluoride sorption

    Sayo Moriyama, Keiko Sasaki, Tsuyoshi Hirajima

    APPLIED CLAY SCIENCE   132   460 - 467  2016年11月  [査読有り]

     概要を見る

    In this study, freeze-drying was applied in the synthesis of nanocrystalline layered double hydroxides (LDHs), and the properties of resulting LDHs along with their efficacies for the removal of fluoride were evaluated. Nano crystalline NO3- and Cl-type LDHs were produced by freeze-drying using liquid N-2. The solid properties of the freeze-dried LDHs were compared with those of LDHs dried at 100 degrees C. Both NO3- and Cl-type LDHs were analyzed via X-ray diffraction (XRD), Fourier transform infrared spectroscopy, Raman spectroscopy, and scanning electron microscopy (SEM). XRD analysis confirmed that the LDHs dried by liquid N-2 were hydrotalcite-like compounds with lower degrees of crystallinity compared with those dried at 100 degrees C. SEM images showed agglomerated nano particles in the freeze-dried LDHs. No significant difference was observed between the NO3- and Cl-type LDHs. However, all characterization results suggested that the freeze-drying method resulted in small nanoparticle sizes. Moreover, bimetallic oxides produced by the calcination of LDHs were affected by the crystallinities of starting materials. Fluoride (F-) sorption experiments on the synthesized LDHs indicated that the freeze-dried LDHs and resulting bimetallic oxides were better sorbents compared with the LDHs prepared at 100 degrees C. The sorption capacities of F- on the LDHs and bimetallic oxides from freeze drying were 0.78-0.87 mM and 4.34 mM, respectively. (C) 2016 Elsevier B.V. All rights reserved.

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  • Sequential modification of montmorillonite with dimethyl dioctadecyl ammonium chloride and benzyl octadecyl dimethyl ammonium chloride for removal of perchlorate

    Wuhui Luo, Akihiro Inoue, Tsuyoshi Hirajima, Keiko Sasaki

    MICROPOROUS AND MESOPOROUS MATERIALS   233   117 - 124  2016年10月  [査読有り]

     概要を見る

    A novel method is reported for surfactant modification of montmorillonite (Mt), and then the performance of the surfactant-modified Mt was investigated for the removal of perchlorate (ClO4 center dot-). Mt was first modified with dimethyl dioctadecyl ammonium chloride (DDAC) under microwave irradiation, which was followed by a second modification with benzyl octadecyl dimethyl ammonium chloride (BODAC). The influence of the added amount of DDAC in terms of ClO4- adsorption to the modified Mt was intensively investigated. In addition, sequential and simultaneous-mixing methods were compared for preparation of the modified Mt in terms of ClO4- removal performance. Using sequential modification, addition of DDAC corresponding to 0.05 times the cation exchange capacity of Mt significantly increased BODAC uptake, resulting in the highest adsorption capacity for ClO4- (1.08 mmol/g). This can be explained by the good balance between the decrease of steric hindrance and the formation of a hydrophobic interface because of adsorbed DDAC. In contrast, for a composite synthesized with the same ratio of DDAC to BODAC, the simultaneous-mixing method resulted in modified Mt with much poorer ClO4- removal performance than the sequential modification method because of the negligible contribution of DDAC to BODAC uptake by Mt. Moreover, a high binding affinity of ClO4- to the sequentially modified composite was obtained because of hydrophobicity of interlaced alkyl chains. (C) 2015 Elsevier Inc. All rights reserved.

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  • Effect of Mg2+ and Ca2+ as divalent seawater cations on the floatability of molybdenite and chalcopyrite

    Tsuyoshi Hirajima, Gde Pandhe Wisnu Suyantara, Osamu Ichikawa, Ahmed Mohamed Elmahdy, Hajime Miki, Keiko Sasaki

    MINERALS ENGINEERING   96-97   83 - 93  2016年10月  [査読有り]

     概要を見る

    Seawater flotation has been applied to mineral processing in areas located far from fresh water resources. However, as seawater has a detrimental effect on molybdenite floatability under alkaline conditions (pH &gt; 9.5), its application in the conventional copper and molybdenum (Cu-Mo) flotation circuit is hindered. A fundamental study of the effect of two divalent cations in seawater, Mg2+ and Ca2+, on the floatability of chalcopyrite and molybdenite is presented in this paper. Floatability tests showed that both MgCl2 and CaCl2 solutions depress the floatability of chalcopyrite and molybdenite at pH values higher than 9. Furthermore, Mg2+ exerts a stronger effect than Ca2+ owing to the adsorption of Mg(OH)(2) precipitates on the mineral surfaces, as indicated by dynamic force microscopy images. The floatability of chalcopyrite was significantly depressed compared with that of molybdenite in a 10(-2) M MgCl2 aqueous solution at pH 11. This phenomenon is likely due to the adsorption of hydrophilic complexes on the mineral surface, which reduces the surface hydrophobicity. A reversal of the zeta potential of chalcopyrite in MgCl2 and CaCl2 solutions at pH 11 and 8, respectively, indicated the adsorption of precipitates onto the surface. In contrast, the zeta potential of molybdenite decreased" continuously under the same conditions. The floatability test of chalcopyrite and molybdenite in mixed systems showed that selective separation of both minerals should be possible with the addition of emulsified kerosene to a 10(-2) M MgCl2 solution at pH 11. A mechanism is proposed to explain this phenomenon. (C) 2016 Elsevier Ltd. All rights reserved.

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  • Microwave-assisted hydrothermal synthesis of nanocrystalline lithium-ion sieve from biogenic manganese oxide, its characterization and lithium sorption studies

    Qianqian Yu, Keiko Sasaki

    HYDROMETALLURGY   165   118 - 124  2016年10月  [査読有り]

     概要を見る

    Biogenic birnessite (BB) is a stable form of manganese oxide. It is widely distributed in the natural environment and originates from microbial oxidation. It has potential applications in functional material fabrication because of its unique morphology. Using a microwave-assisted hydrothermal method, nano-sized lithium-ion sieves were prepared from BB with a short reaction time. A combination of sorption experiments and structural characterization was used to compare Li uptake by nanoparticles with that by microparticles. X-ray diffraction (XRD) patterns showed that the nano-and microparticles had similar fundamental structures, but the lattice parameter of nanopartides is smaller than micropartides. Mn K-edge X-ray absorption fine structure (XAFS) spectroscopy showed that the oxidation state of Mn increased from 3.50 to 3.69 with decreasing crystal size, and the Mn-Mn atomic distance decreased from 2.92 to 2.89 angstrom. Li extraction resulted in significant cleavage of the micropartide surfaces. The oxidation state of Mn increased to 4.0, and the Mn-Mn atomic distance decreased to 2.86 angstrom. XRD showed that dissolution of the polycrystalline phase of the nanopartides occurred during acid washing. However, the EXAFS spectrum was similar to that of the original material before acid washing. The specific surface areas and U-sorption capacities of the nano-sized lithium-ion sieves prepared from manganese carbonate were significantly higher than those of a similarly prepared micro-sized lithium-ion sieve. The results obtained in this work suggest that BB is a promising starting material for the energy-saving fabrication of functional materials for highly efficient Li recovery. (C) 2015 Elsevier B.V. All rights reserved.

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  • Combustion performance of Loy Yang lignite treated using microwave irradiation treatment

    Xiangchun Liu, Taigen Masuyama, Tsuyoshi Hirajima, Moriyasu Nonaka, Keiko Sasaki

    THERMOCHIMICA ACTA   642   81 - 87  2016年10月  [査読有り]

     概要を見る

    The combustion characteristics and activation energy of the microwave irradiation (MI) treated lignite were investigated by thermogravimetric analysis at different heating rates. Effects of the changes in physicochemical properties (amounts of volatile matter and fixed carbon, specific surface area, and pore volume) on the combustion performance were also discussed. The activation energy was calculated using the Kissinger-Akahira-Sunose isoconversional method. The results showed that ignition temperature of the MI treated samples increased significantly relative to that of raw lignite, and it gradually increased with increasing MI time, indicating that MI treatment decreases the reactivity of lignite, which progressively decreases as MI time increases. The maximum combustion rates of the treated samples were higher than that of raw lignite, suggesting that MI treatment modifies the combustion intensity of Loy Yang lignite. Moreover, the combustion processes of samples treated by MI for 5 and 7 min were single rate-limiting step kinetics, whereas raw lignite and samples treated by MI for 3 and 9 min followed multistep kinetics. Average activation energy for sample treated using MI for 5 min was the maximum value, and it decreased with further increasing MI time because of the increased effect of diffusion. (C) 2016 Elsevier B.V. All rights reserved.

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  • Interfacial effects of MgO in hydroxylated calcined dolomite on the co-precipitation of borates with hydroxyapatite

    Keiko Sasaki, Kenta Toshiyuki, Keiko Ideta, Jin Miyawaki, Tsuyoshi Hirajima

    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS   504   1 - 10  2016年09月  [査読有り]

     概要を見る

    Hydroxylated calcined dolomite (HCD) is used as a mineralizer to immobilize borates by co-precipitation with hydroxyapatite (HAp). HCD sometimes includes appreciable quantities of MgO depending on the degree of hydroxylation of the calcined dolomite. In this work, the interfacial effects of MgO in HCD on the removal kinetics of borates were examined using Ca(OH)(2) and HCDs with different degrees of hydroxylation. As the fraction of MgO phases within the HCD increased, the borate immobilization rate stagnated because the formation of hydroxyapatite (HAp) was inhibited. This effect arose from the interaction of boric acid (H3BO3) with the MgO in HCD, followed by hydroxylation to cover the Ca(OH)(2) surfaces with newly formed Mg(OH)(2). In the presence of borate, the unstable intermediate [MgB(OH)(4)](+) complex was formed through ligand-promoted dissolution of MgO in the HCD. B-11 NMR spectra revealed that the stagnation in immobilization of tetragonal boron (NB) species was observed for up to 45 min, accompanied by the suppression of HAp formation. TEM images of the HCD suggested that Ca(OH)(2) was partially associated with MgO and Mg(OH)(2) phases within the HCD and hydroxylation of MgO led to a thin covering of the surface of Ca(OH2 with the newly formed gel phases comprising Mg(OH)(2)/H3BO3 that hinders the dissolution of Ca(OH)(2). However, when MgO was completely hydroxylated in the HCD this delay was not observed. This was supported by zeta potential measurements on the solid residues during co-precipitation. The results suggest that the degree of hydroxylation of the calcined dolomite in HCD markedly influences the co-precipitation kinetics of borates in industrial water treatment. (C) 2016 Elsevier B.V. All rights reserved.

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  • Microbial recovery of vanadium by the acidophilic bacterium, Acidocella aromatica.

    Naoko Okibe, Masashi Maki, Daisuke Nakayama, Keiko Sasaki

    Biotechnology letters   38 ( 9 ) 1475 - 81  2016年09月  [査読有り]  [国際誌]

     概要を見る

    OBJECTIVE: To investigate the bioreduction of toxic pentavalent vanadium [vanadate; V(V)] in the acidophilic, Fe(III)-reducing obligately heterotrophic bacterium, Acidocella aromatica PFBC. RESULTS: Although the initial lag-phase of growth became extended with increasing initial V(V) concentrations, the final cell density during aerobic growth of A. aromatica PFBC was unaffected by up to 2 mM V(V). While strain PFBC is an aerobe, growth-decoupled PFBC cell suspensions directly reduced V(V) using fructose, both micro-aerobically and anaerobically, under highly acidic (pH 2) and moderately acidic (pH 4.5) conditions. Bio reduced V(IV) was subsequently precipitated even under micro-aerobic conditions, mostly by encrusting the cell surface. An anaerobic condition at pH 4.5 was optimal for forming and maintaining stable V(IV)-precipitates. Recovery of approx. 70 % of V(V) from the solution phase was made possible with V(V) at 1 mM. CONCLUSIONS: The first case of direct V(V) reducing ability and its subsequent V recovery from the solution phase was shown in acidophilic prokaryotes. Possible utilities of V(V) bioreduction in acidic conditions, are discussed.

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  • Effect of kerosene emulsion in MgCl2 solution on the kinetics of bubble interactions with molybdenite and chalcopyrite

    Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Ahmed Mohamed Elmahdy, Hajime Miki, Keiko Sasaki

    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS   501   98 - 113  2016年07月  [査読有り]

     概要を見る

    The formation of stable bubble-particle aggregates is essential to the froth flotation process. To form such aggregates, bubbles and particles must collide, the intervening liquid film must be drained below its critical rupture thickness, and three-phase contact (TPC) formation must occur. A good understanding of the interaction mechanism between bubbles and particles during collision and attachment is important. We herein investigated the effects of emulsified kerosene in a 0.01 M MgCl2 solution (a model seawater component) on bubble interactions with pure molybdenite (MoS2) and chalcopyrite (CuFeS2) surfaces. In 0.01 M MgCl2 at pH 6 and 11, kerosene retarded the bubble surface mobility and reduced the bubble rise velocity. In the presence of kerosene at pH 6, the TPC formed more rapidly on both mineral surfaces. This was due to the increase in surface hydrophobicity caused by kerosene. In addition, TPC formation was more rapid on the molybdenite surface than on the chalcopyrite surface due to the effect of the adsorbed kerosene and the low surface homogeneity of molybdenite. Finally, floatability tests demonstrated that the separation of molybdenite and chalcopyrite should be possible by adding emulsified kerosene in a 0.01 M MgCl2 solution at pH 9. (c) 2016 Elsevier B.V. All rights reserved.

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  • Catalytic effect of silver on arsenic-containing copper sulfide dissolution in acidic solution

    Hajime Miki, Akinobu Iguchi, Tsuyoshi Hirajima, Keiko Sasaki

    HYDROMETALLURGY   162   1 - 8  2016年06月  [査読有り]

     概要を見る

    Catalytic effects of silver on the dissolution of arsenic-containing copper sulfides such as enargite in acidic media were investigated. Leaching experiments showed that silver increased the enargite dissolution rate, and that the dissolution behavior was potential-dependent. The addition of silver ions and silver sulfide greatly enhanced enargite dissolution. Such behavior can be explained based on the following reaction model: enargite dissolution is enhanced by silver as the silver ions remove the hydrogen sulfide produced during enargite reduction, giving the more amenable copper sulfide. Thermodynamic calculations suggested that the addition of silver ions and controlling the potential would maintain a high enargite dissolution rate. Leaching experiments were therefore performed with the addition of silver sulfide and potential control using an automatic titration apparatus. Experimental results showed that a combination of these two factors gave high enargite dissolution; i.e., 75% copper was dissolved in 24 hat 0.750-0.850 V vs. the standard hydrogen electrode at 303 K. (C) 2016 Elsevier B.V. All rights reserved.

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  • Synthesis of morphologically controlled hydroxyapatite from fish bone by urea-assisted hydrothermal treatment and its Sr2+ sorption capacity

    Tomoyo Goto, Keiko Sasaki

    POWDER TECHNOLOGY   292   314 - 322  2016年05月  [査読有り]

     概要を見る

    Needle- and sponge-shaped hydroxyapatite (HAp) particles were synthesized from calcined tuna fish bone (Tn1000) and commercially available HAp reagent (ChemHAP) by a urea-assisted hydrothermal treatment using 0.1-1.0 M urea solution at 160 degrees C for 3 h. The Sr2+ sorption capacity of the synthesized HAp was also investigated using 0-50 mM Sr2+ solution at 25 degrees C for 72 h to evaluate its performance as a sorbent for environmental remediation. Sponge-shaped HAp was formed under hydrothermal conditions with a urea concentration of 1.0 M. With decreasing urea concentration, the morphology of HAp changed from sponge-shaped to needle shaped crystals, regardless of the starting material. Some calcium carbonate and/or beta-tricalcium phosphate impurities were formed from Tn1000 at 0.1-0.5 M urea concentration. The Sr2+ sorption mechanism of the synthesized HAp was estimated using Ca ion-exchange reaction and precipitation of SrCO3. The sponge-shaped HAp crystals, which had high specific surface area and CO32- content, exhibited a large ion-exchange capacity with Sr2+ In contrast, the ion-exchange ratio of needle-shaped HAp dramatically decreased with increasing initial Sr concentration. No clear difference in Sr2+ sorption behaviour caused by the choice of HAp synthesis starting material was observed. These results indicate that the Sr sorption mechanism of HAp is influenced by not only its composition but also its crystal morphology. (C) 2016 Elsevier B.V. All rights reserved.

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  • Comparison of atmospheric citric acid leaching kinetics of nickel from different Indonesian saprolitic ores

    Widi Astuti, Tsuyoshi Hirajima, Keiko Sasaki, Naoko Okibe

    Hydrometallurgy   161   138 - 151  2016年05月  [査読有り]

     概要を見る

    © 2016 Elsevier B.V. All rights reserved. Saprolitic ores from Sulawesi Island (SS ore) contain serpentine and goethite as major minerals, whereas the main minerals in saprolitic ore from Halmahera Island (SH ore) are talc and goethite. Most of the nickel was incorporated in a magnesium-silica-containing mineral. The effects on nickel extraction of leaching temperature, citric acid concentration, and ore particle size were determined to investigate the leaching performances and leaching kinetics of the two saprolitic ores. Nickel leaching efficiency from SS ore is always higher than that from SH ore under the same leaching conditions. The mineral contents of the ores significantly affected the leaching performances and mineral dissolution behaviors of the samples. The results of nickel leaching efficiency and analysis of the solid residues suggest that all dissolved nickel originated from serpentine, which is more easily leached than goethite and talc. The rate of nickel extraction for SS ore was faster than that for SH ore. Nickel leaching from SS ore and SH ore followed the shrinking-core model and was controlled by diffusion of a reactant or product through the solid product layer.

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    25
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  • Direct determination of lignin peroxidase released from Phanerochaete chrysosporium by in-capillary enzyme assay using micellar electrokinetic chromatography

    Airi Harada, Keiko Sasaki, Takashi Kaneta

    JOURNAL OF CHROMATOGRAPHY A   1440   145 - 149  2016年04月  [査読有り]

     概要を見る

    Here we describe the application of an in-capillary enzyme assay using micellar electrokinetic chromatography (MEKC) in the determination of enzyme activity in a crude culture medium containing lignin peroxidase released from Phanerochaete chrysosporium (P. chrysosporium). The method consists of a plug-plug reaction between lignin peroxidase and its substrate, veratryl alcohol, the separation of the product, veratraldehyde, from the other components including the enzyme and the culture medium, and the determination of the enzyme activity from the peak area of veratraldehyde produced by the plug-plug reaction. This method is more sensitive than conventional spectrophotometry since the background originates from the enzyme and the culture medium can be removed via MEKC separation. Veratraldehyde was separated at-10 kV in a background electrolyte containing 50mM tartrate buffer (pH 2.5) and 50 mM sodium dodecyl sulfate (SDS) after a plug-plug reaction in the capillary for 5 min. The calibration curve of veratraldehyde was linear up to 4pmol (500 mu M) with a limit to quantification of 0.026 pmol (3.211 mu M) (SN = 10). The activity of lignin peroxidase was directly measured from the peak area of veratraldehyde. The activity of lignin peroxidase released from P. chrysosporium into the medium for 7 days was successfully determined to be 3.40 UL-1. (C) 2016 Elsevier B.V. All rights reserved.

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    7
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  • Optimization of hexadecylpyridinium-modified montmorillonite for removal of perchlorate based on adsorption mechanisms

    Wuhui Luo, Tsuyoshi Hirajima, Keiko Sasaki

    APPLIED CLAY SCIENCE   123   29 - 36  2016年04月  [査読有り]

     概要を見る

    Adsorption of perchlorate (ClO4-) onto hexadecylpyridinium-modified montmorillonite (OMt) was investigated by in situ and ex situ methods. For the in situ method, ClO4- was initially bound by hexadecylpyridinium (HDPy+) in the form of HDPy-ClO4 which together with the excess HDPy+ were simultaneously captured by Mt. The ex situ strategy was performed by adding synthesized OMt into ClO4- bearing solution, where conventionally dried OMt (II-OMt) and innovative OMt (I-OMt) without drying and washing procedure were compared as adsorbents. The adsorption capacity of CLOT and amount of HDPy released into equilibrium solution were evaluated, where surfactant release was rarely addressed in previous publications. I-OMt showed relatively high adsorption capacity of ClO4- and negligible release of HDPy. The lower adsorption capacity of ClO4- onto II-OMt was caused by the washing procedure which removed the unstably anchored HDPy. Inhibition of HDPy release of I-OMt was explained by reconfiguration of HDPy after ClO4- adsorption as supported by results of X-ray diffraction and attenuated total reflection Fourier transform infrared spectroscopy. In addition, for anion adsorption onto conventionally synthesized OMt, the difference between the amounts of released counter ion and that of entrapped target anion is generally ignored. Such phenomenon was critically considered in this study, and the results showed that the difference between adsorbed ClO4- and released Cl- decreased with an increase of HDPy loading and was more significant in I-OMt. This is rationalized by the desorption of HDPy+ and formation of HDPy-ClO4- according to the results of C-13 nuclear magnetic resonance spectra and the adsorption energy evaluated by the Dubinin-Radushkevich model. (C) 2016 Elsevier B.V. All rights reserved.

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    25
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  • Removal mechanism of high concentration borate by co-precipitation with hydroxyapatite

    Keiko Sasaki, Kenta Toshiyuki, Keiko Ideta, Hajime Miki, Tsuyoshi Hirajima, Jin Miyawaki, Mitsuhiro Murayama, Ismaila Dabo

    Journal of Environmental Chemical Engineering   4 ( 1 ) 1092 - 1101  2016年03月  [査読有り]

     概要を見る

    Co-precipitation of borate in a wide range of concentration with hydroxyapatite (HAp) was investigated using Ca(OH)2 as a mineralizer in the presence of phosphate. The sorption data of borate was fitted to Freundlich model. The maximum sorption density of B/Ca to maintain a mono-phase of HAp was found around 0.40. In higher B concentrations, borate was still immobilized, however, the crystalization of hydroxyapatite was inhibited, where the solid residues were accompanied with amorphous CaB2O4, as well as HAp. Based on 11B-NMR and elemental analysis for solid residues in addition to solution chemistry, the removal mechanism of high concentration borate can be explained by the surface complexation of triborate on Ca(OH)2, subsequently decomposition of triborate into monoborate to release [CaB(OH)4]+ and B(OH)4 -, followed by co-precipitation with HAp. These tetragonal B species were immobilized in the solid residues including amorphous HAp. During the process there was a trend to eliminate carbonate from the solid phase. TEM images suggested that the HAp particles precipitated at room temperatures were in a fibrous shape consisting of a number of short rods when borate species are not added. When borate species were immobilized, the HAp particles have gotten swelled with losing fibrous shapes. When further higher borate concentrations were encapsulated in co-precipitated products, the morphologies were dramatically changed, that is, nano-sized and less crystalline HAp particles were enveloped by possibly amorphous CaB2O4.

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    17
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  • Fe3O4/MgAl-NO3 layered double hydroxide as a magnetically separable sorbent for the remediation of aqueous phosphate

    Paulmanickam Koilraj, Keiko Sasaki

    Journal of Environmental Chemical Engineering   4 ( 1 ) 984 - 991  2016年03月  [査読有り]

     概要を見る

    The separation of a spent sorbent from treated water after remediation is one of the major difficulties associated with industrial scale water treatment methods. Fe3O4 particles offer an easy magnetic method for the separation of used sorbent from water. Due to its low sorption capacity, magnetic Fe3O4 particles were first modified with Mg2Al-NO3-LDH prior to use in phosphate remediation. The Fe3O4/Mg2Al-NO3-LDH composite materials showed a maximum sorption capacity of 33.4 mgP/g while Fe3O4 particles alone recovered only 4.6 mgP/g. The kinetics of phosphate sorption onto Fe3O4/Mg2Al-NO3-LDH follows the pseudo-second order kinetic model supported by the best linear regression coefficient value (R2 - 1.00). Sorption isotherm studies indicated that it follows the Langmuir monolayer sorption isotherm. The effect of pH and competing anion studies indicate that this material is highly efficient in a wide pH range (pH 3-10). Selective sorption of phosphate on Fe3O4/Mg2Al-NO3-LDH was observed in the presence of excess sulfate, as well as from sea water enriched with phosphate. Fe3O4/Mg2Al-NO3-LDH composite material offers easy separation of spent sorbents due to magnetic property. The retention of sorption capacity in a wide pH range, and selectivity in the presence of competing anion, as well as from sea water suggests that these composite magnetic materials will be effective for wastewater remediation.

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    43
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  • Removal mechanism of high concentration borate by co-precipitation with hydroxyapatite

    Sasaki Keiko, Toshiyuki Kenta, Ideta Keiko, Miki Hajime, Hirajima Tsuyoshi, Miyawaki Jin, Murayama Mitsuhiro, Dabo Ismaila

    JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING   4 ( 1 ) 1092 - 1101  2016年03月  [査読有り]

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    17
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  • Fe3O4/MgAl-NO3 layered double hydroxide as a magnetically separable sorbent for the remediation of aqueous phosphate

    Koilraj Paulmanickam, Sasaki Keiko

    JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING   4 ( 1 ) 984 - 991  2016年03月  [査読有り]

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    43
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  • Influence of Mg Components in hydroxylated calcined dolomite to (co-)precipitation of fluoride with apatites

    Kenta Toshiyuki, Shugo Nagato, Tsuyoshi Hirajima, Keiko Sasaki, Takuro Naruse, Takeshi Kawashima

    CHEMICAL ENGINEERING JOURNAL   285   487 - 496  2016年02月  [査読有り]

     概要を見る

    Hydroxylated calcined dolomite (HCD) is practically used as a mineralizer to immobilize fluoride by co-precipitation with hydroxyapatite (HAp) and precipitation as fluoroapatite (FAp). It has an advantage to remove fluoride without stagnation, which is always observed with Ca(OH)(2) alone. HCD includes a certain content of MgO and Mg(OH)(2) as well as Ca(OH)(2). In the present work, the mechanism to explain the enhancing role of Mg components on removal kinetics of fluoride was aimed to elucidate. Nano-domain observation approaches were conducted by TEM when Ca(OH)(2) is added as a Ca source in the presence of different Mg2+ concentrations, instead of HCD. With increase in Mg2+ concentrations in the presence of Ca (OH)(2), removal rate of fluoride was enhanced. The enhancement was also observed with HCD. Mg2+ and [Mg(OH)](+) species, which can be derived from HCD, are adhered to the negatively charged c-plane of freshly formed amorphous HAp/FAp and CaCO3. As a result, the surface of Ca(OH)(2) particles are gotten rid of hetero-coagulation with HAp/FAp and CaCO3 in the presence of Mg2+ and [Mg(OH)](+) species, and maintained to release Ca2+ and OH- ions, facilitating to precipitate HAp and FAp for immobilization of fluoride. Without Mg2+ additives the Ca(OH)(2) surfaces are blocked by insoluble HAp/FAp through hetero-coagulation. This interpretation is also supported by TEM observation, which is well consistent with XRD results. The findings indicate that MgO and Mg(OH)(2) contents in HCD influence the removal kinetics of fluoride by (co-)precipitation as apatites in industrial water treatment. Understanding the surface science in nano-domain is important in parallel reactions of dissolution and precipitation. (C) 2015 Elsevier B.V. All rights reserved.

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    10
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  • Hydrothermal carbonization kinetics of sugarcane bagasse treated by hot compressed water under variabel temperature conditions

    Iryani, D.A., Kumagai, S., Nonaka, M., Sasaki, K., Hirajima, T.

    ARPN Journal of Engineering and Applied Sciences   11 ( 7 )  2016年

  • Effect of kerosene on bubble interaction with molybdenite and chalcopyrite in MgCl<inf>2</inf> solution

    Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, A. M. Elmahdy, Hajime Miki, Keiko Sasaki

    IMPC 2016 - 28th International Mineral Processing Congress   2016-September  2016年

     概要を見る

    Seawater has been reported to depress molybdenite in a copper-molybdenum (Cu-Mo) flotation process at high pH due to the precipitation of Mg(OH)2. Meanwhile, to improve mineral recoveries, collectors are usually added into the flotation cells, thus adding the complexity to the mechanism of bubble-particle interactions involved in Cu-Mo flotation. Therefore, understanding the interaction mechanism in seawater flotation and in the presence of collectors is important to explain the minerals depression. The present work investigated the effect of kerosene on the bubble collision and attachment to pure chalcopyrite and molybdenite surfaces in MgCl2 solution as one of the seawater major components at pH 6 and 11. Mineral surfaces were characterized using atomic force microscopy (AFM). In addition, minerals floatability in the same system were tested in a column flotation. The study of bubble-particle interactions shows that following several collisions, bubble could displace the intervening liquid layer on the mineral surfaces, forming a three-phase contact (TPC). A TPC formed more rapidly in the presence of emulsified kerosene in a 0.01 M MgCl2 solution at pH 6 for both minerals. The reason is kerosene increased the surfaces hydrophobicity and destabilized the intervening liquid layer on the surfaces. Moreover, the average time required to form a TPC was shorter on molybdenite surface. This can be attributed to the effect of adsorbed kerosene on molybdenite surface and molybdenite surface roughness.

  • Comparison of selective flotation of chalcopyrite and molybdenite with various oxidation techniques

    Tsuyoshi Hirajima, Hidekazu Matsuoka, Hajime Miki, Gde Pandhe Wisnu Suyantara, Ahmed Mohamed Elmahdy, Keiko Sasaki

    IMPC 2016 - 28th International Mineral Processing Congress   2016-September  2016年

     概要を見る

    Selective flotation of chalcopyrite and molybdenite was studied using various surface treatment methods such as electrolysis, ozone treatment, and plasma. Oxidation via electrolysis method indicated that only chalcopyrite surface is affected by electrolysis due to conductivity difference with molybdenite. Oxidation treatments and XPS analyses indicated that chalcopyrite became hydrophilic due to deposition of oxidized iron on its surface. Various oxidizing methods also showed that chalcopyrite was selectively oxidized and this can apply selective flotation of chalcopyrite and molybdenite. The possible mechanisms are proposed in this work based on surface analyses and thermodynamic calculations.

  • 信号処理と判別分析法を用いた 廃蛍光管の分類

    太屋岡 篤憲, 太屋岡 恵里子, 平島 剛, 笹木 圭子

    Journal of MMIJ   132 ( 3 ) 53 - 58  2016年

     概要を見る

    Recycling high-purity rare earths from the waste in fluorescent lamps will assist in preserving rare earth resources. However, the present recovery from the waste in fluorescent lamps is very low at around 30%, and most waste fluorescent lamps are reclaimed. In this study we attempted to reduce one cause of difficulty in recycling lamps, namely the identification of rare earths in plastic-covered lamps, which is conventionally executed by human operators. Using the Acoustic Emission (AE) signal of the collision sound between lamps and an AE sensor head, we first carried out waveform analysis, and frequency analysis using the discrete Fourier transform. We extracted six feature values for each analysis and differentiated the plastic-covered lamps using thresholds. The least error rates were 4.85% and 6.67% for the waveform and frequency analyses, respectively. Second, we applied discriminant analysis on the six feature values from each analysis, resulting in error rates of 3.03% and 5.45%, respectively. Third, we extracted six feature values from the time-frequency analysis using the discrete Wavelet transform and Fractal dimensioning, and applied discriminant analysis on the six feature values, resulting in an error rate of 4.24%. Finally, we examined all the results from the three analyses to find the best combination of feature values, applied discriminant analysis to 12 feature values from the time analysis and time-frequency analysis, and succeeded in reducing the error rate to 0%.

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  • Hydrothermal treatment coupled with mechanical expression for Loy Yang lignite dewatering and the microscopic description of the process

    Xiangchun Liu, Tsuyoshi Hirajima, Moriyasu Nonaka, Keiko Sasaki

    DRYING TECHNOLOGY   34 ( 12 ) 1471 - 1483  2016年  [査読有り]

     概要を見る

    The changes in the gaseous, liquid, and solid products obtained from hydrothermally treated lignite and hydrothermally treated solid products treated by the following mechanical expression were investigated. Furthermore, a microscopic description of the changes was present. Gaseous, liquid, and solid products were characterized by gas chromatography, total organic carbon analyzer, inductively coupled plasma atomic emission spectroscopy, high-performance liquid chromatography, and Fourier transform infrared spectrometer, respectively. The results showed that at temperatures above 173 degrees C for hydrothermal treatment, freezable water, and some organic and inorganic compounds were removed from lignite, and acidic groups first dissolved and decomposed at 100 degrees C. For the following mechanical expression treatment, freezable and nonfreezable water and organic and inorganic compounds were removed, and the concentration of acidic groups changed little. Within temperatures range 175-250 degrees C, for hydrothermal treatment, nonfreezable water and inorganic and organic compounds continued to be removed, and the detection of CO2 is because of decarboxylation. For the following mechanical expression treatment, the main removed water was nonfreezable water, and changes in organic and inorganic compounds, acidic groups, and volatile matter were similar to that of samples treated by mechanical expression at temperatures below 173 degrees C.

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  • Use of FTIR combined with forms of water to study the changes in hydrogen bonds during low-temperature heating of lignite

    Xiangchun Liu, Tsuyoshi Hirajima, Moriyasu Nonaka, Anggoro Tri Mursito, Keiko Sasaki

    DRYING TECHNOLOGY   34 ( 2 ) 185 - 193  2016年  [査読有り]

     概要を見る

    The changes in the hydrogen bonds (HBs) of three types of Indonesian lignite during low-temperature heating were investigated. The amount of water loss was determined by weighing the samples before and after heating in an oven. The changes in the number of the different types of HBs were determined using Fourier transform infrared spectroscopy coupled with types of water in lignite. The number of peak positions and absorption bands in each spectrum was determined by curve-fitting analysis with a Gaussian function. The quantified integrated area of aromatic hydrogen atoms was used to accurately investigate the changes in the HBs. The results show that at low temperatures (T50 degrees C), free water is mainly removed, and the HBs broken are those between free water molecules. However, at medium temperatures (50 &lt;T 100 degrees C), bound water is mainly removed. The number of HBs significantly changes because of the breaking of bound water molecule HBs and bound water cluster-carboxyl group HBs, and the formation of nonfreezable moisture HBs. At high temperatures (100 &lt;T&lt;125 degrees C), nonfreezable moisture can be released. The number of HBs changes as a result of competition between the removal of nonfreezable moisture and the increase in the number of carboxyl groups. At higher temperatures (T125 degrees C), the moisture remaining in lignite is thermal decomposition moisture. In addition, the rate of decomposition of carboxyl groups is higher than the rate of generation, which means that the number of HBs markedly decreases at higher temperatures.

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  • Comparison of effectiveness of citric acid and other acids in leaching of low-grade Indonesian saprolitic ores

    Widi Astuti, Tsuyoshi Hirajima, Keiko Sasaki, Naoko Okibe

    Minerals Engineering   85   1 - 16  2016年01月  [査読有り]

     概要を見る

    © 2015 Elsevier Ltd. All rights reserved. Comparison effect of chemical citric acid and other leaching reagents including inorganic acid and other organic acid on nickel extraction from low-grade Indonesian saprolitic ores was evaluated. Two saprolitic ores from two different mining areas (Sulawesi Island and Halmahera Island) in Indonesia were used to investigate the leaching performance and mineral dissolution behaviors of different ore samples using different leaching reagents. Leaching was performed using citric, sulfuric, nitric, hydrochloric, lactic, and oxalic acids. The saprolitic ore from Sulawesi Island (SS) has higher serpentine and lower goethite contents than the saprolitic ore from Halmahera Island (SH). These differences significantly affect the leaching performances and metal dissolution behaviors. Citric acid and sulfuric acid were more effective than other acid solutions for nickel extraction from both samples. Citric acid was very effective for dissolving nickel from serpentine, but did not recover nickel from goethite. In contrast, inorganic acids, namely sulfuric, nitric, and hydrochloric acids, can extract nickel from lateritic ores by dissolving goethite as well as serpentine, but the nickel recoveries achieved with sulfuric acid were higher than those achieved with other inorganic acids. A comparison of the leaching performances of the two samples shows that nickel recovery from SS was higher than that from SH when citric acid leaching was used, but the samples gave similar nickel recoveries in all inorganic acid and lactic acid leaching processes. Moreover, oxalic acid is the least effective reagent for nickel extraction from both samples, because of nickel oxalate precipitation after nickel dissolution. In addition, the effect of a sulfuric acid-citric acid mixture on the nickel dissolution rate was investigated to confirm the individual influences of citric acid and sulfuric acid on the leaching behavior of each sample. The results show that an increase in the amount of sulfuric acid affected the dissolution rate of nickel in leaching of SH much more than that in leaching of SS. In general, the effect of citric acid in the mixture of sulfuric acid and citric acid is attractive. Moreover, citric acid offers not only high nickel recovery and high selectivity of leaching but also an environmentally safe process and low acid consumption.

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  • Effect of Hydrothermal Treatment Coupled with Mechanical Compression on Equilibrium Water Content of Loy Yang Lignite and Mechanism

    Xiangchun Liu, Tsuyoshi Hirajima, Moriyasu Nonaka, Keiko Sasaki

    MATERIALS TRANSACTIONS   57 ( 6 ) 935 - 942  2016年  [査読有り]

     概要を見る

    Measurements of equilibrium water contents (EWCs) in samples obtained from hydrothermal treatment (HT) and HT coupled with mechanical compression (HT-MC) were undertaken across a range of relative humidities (RHs) to investigate the performance of EWC and its mechanism. The changes in the concentrations of carboxyl groups and mesopore volume were measured by an improved barium ion exchange and N-2 adsorption-desorption isotherms methods, respectively. The results showed that EWCs decreased with progressively severe HT and HT-MC conditions and EWCs of HT-MC samples were lower than those of HT samples, indicating that HT and HT-MC can upgrade lignite by reducing water loading capacity and HT-MC was better than HT. At low RHs (RH &lt;= 10%), the factor that controls EWC is water molecules-active sites interactions and one to two water molecules are associated with each carboxyl group, while at medium RHs (10 &lt; RH &lt;= 92%) the amount of monolayer water and mesopore volume gain in significance and ca. two multilayer water molecules are bound to each monolayer water molecule. At high RHs (RH &gt; 92%), EWC is determined by comprehensive factors such as macropores and cracks. Furthermore, EWC can be either higher or lower than residual water content (RWC) based on the RH within a threshold residual water level (ca. 5 to 16%). EWC was generally higher than RWC below a RWC of ca. 5% and the opposite relationship was observed for samples with RWC above ca. 16%. These provide information for the operation of lignite dewatering technique, the control of its water re-adsorption, and storage.

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  • Suppression of pyrite oxidation in acid mine drainage by carrier microencapsulation using liquid product of hydrothermal treatment of low-rank coal, and electrochemical behavior of resultant encapsulating coatings

    Mutia Dewi Yuniati, Keitaro Kitagawa, Tsuyoshi Hirajima, Hajime Miki, Naoko Okibe, Keiko Sasaki

    Hydrometallurgy   158   83 - 93  2015年12月  [査読有り]

     概要を見る

    © 2015 Elsevier B.V. Pyrite is a mineral sulfide found extensively in acid mine drainage; this is one of the most serious environmental problems in the mining industry. Suppression of pyrite oxidation via carrier microencapsulation (CME) with silicon (Si) and organic carriers has been proposed. In the present study, use of the hydrothermal treatment liquid (HTL) produced from low-rank coal as a carrier in CME was investigated. In dissolution tests for 51 days with pyrite and iron-oxidizing bacteria, treatment with a mixture of HTL and a silicon reagent (Si-HTL) lowered the ferric ion concentration and limited bacterial attachment compared with untreated pyrite. This might be caused by catechol present in the HTL. A mixture of catechol and a silicon reagent (Si-Cat) was also used, and the coatings obtained using Si-HTL and Si-Cat were compared. The electrochemical behavior of the treated pyrite samples showed oxidative decomposition of the Si-Cat complex and formation of an encapsulating layer at 690 mV for Si-HTL and 550 mV for Si-Cat. The two semi-circular curves in the Nyquist plot simulations showed that the total impedances of the treated pyrite samples increased. Microscopic observations showed that the oxidative layer was silica rich. These data indicate that a silica-quinone coating is created and the pyrite oxidation rate can be suppressed by pretreatment with either Si-HTL or Si-Cat for 1 h.

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  • Removal mechanism of polymeric borate by calcined layered double hydroxides containing different divalent metals

    Xinhong Qiu, Keiko Sasaki

    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS   482   702 - 709  2015年10月  [査読有り]

     概要を見る

    The removal mechanism of polymeric borate by calcined layered double hydroxides is not clear. In this work, layered double hydroxides containing different divalent metals were synthesized and calcined to produce calcined layered double hydroxides (Zn-, Mg-, and Ca-CLDH). Then, Zn-, Mg-, and Ca-CLDH were applied to remove polymeric borate. Zn-CLDH showed better performance for the removal of borate than Ca-CLDH, and hardly any borate was removed by Mg-CLDH. Based on the characterization results, the detailed removal process of polymeric borate by different calcined layered double hydroxides is discussed. Because there is little H3BO3 that can act as a trigger, and ligand promoted dissolution of the complex H3BO3 and MgO is prevented. Therefore, Mg-CLDH could not transform to the layered structure to immobilize the borate. For the Zn-CLDH, Zn-CLDH transformed into Zn-LDH, and polymeric borate was absorbed into the interlayer of layered double hydroxides, which is the dominant mechanism of borate removal by Zn-CLDH. Reconstruction of the Ca-LDH from the Ca-CLDH was more rapid than the other calcined layered double hydroxides. However, formation of borate-containing ettringite was the main removal mechanism in the first stage. With increasing reaction time, the reaction between CO32- and Ca2+ released from ettringite, and the regeneration of Ca-LDH to form CaCO3 were the main reasons for borate removal in the second stage. (C) 2015 Elsevier B.V. All rights reserved.

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    7
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  • Effects of initial Fe2 + concentration and pulp density on the bioleaching of Cu from enargite by Acidianus brierleyi (vol 109, pg 153, 2011)

    Keiko Sasaki, Koichiro Takatsugi, Tsuyoshi Hirajima

    HYDROMETALLURGY   157   178 - 178  2015年10月  [査読有り]

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  • Silicate Covering Layer on Pyrite Surface in the Presence of Silicon-Catechol Complex for Acid Mine Drainage Prevention

    Mutia Dewi Yuniati, Tsuyoshi Hirajima, Hajime Miki, Keiko Sasaki

    MATERIALS TRANSACTIONS   56 ( 10 ) 123 - 131  2015年10月  [査読有り]

     概要を見る

    In this paper, prevention of pyrite oxidation by carrier microencapsulation (CME) was investigated. A possible layer structure was suggested following analysis with electrochemical and surface analysis techniques. Electrochemical study of treated pyrite samples showed that treatment with silicon catechol (Si-Cat) for 6h at an initial pH of 9.5 gave the best barrier properties and suppression of the samples. Scanning electron microscopy with energy-dispersive X-ray, and Fourier transform infrared (FUR) analyses confirmed the presence of a silicate layer on the surface of treated pyrite. X-ray photoelectron spectroscopy indicated that the coating layers on the treated pyrite samples consisted of a network of Fe-O-Si and Si-O-Si units bonded to the surface of pyrite. The Si-O-C asymmetric stretching mode was also observed in FTIR spectra. Detailed spectroscopic analyses confirmed the formation of a silicate polymer on a silica quinone layer, which resulted in the effective suppression effect shown by Si-Cat-treated pyrite at increasing pH.

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    20
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  • Surfactant-modified montmorillonite by benzyloctadecyldimethylammonium chloride for removal of perchlorate

    Wuhui Luo, Keiko Sasaki, Tsuyoshi Hirajima

    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS   481   616 - 625  2015年09月  [査読有り]

     概要を見る

    A high adsorption capacity (0.90 mmol/g) of perchlorate was achieved on organo-montmorillonites (organo-MMTs) through modification by benzyloctadecyldimethylammonium chloride (BODMA-Cl), which typically possesses a long alkyl chain and a benzene ring. With increase in the amount of BODMA-Cl added, the XRD and FTIR results showed that the BODMA(+)/BODMA-Cl achieved a lateral bilayer, pseudo-trilayer and tilted paraffin-like bilayer configurations in the MMT interlayer space with improvement of ordered arrangement, and the formation of bilayers and/or micelles on the external surface also was demonstrated by TG-DTA and zeta potential curves. The EDX spectra of resultant products and adsorption isotherms of perchlorate on organo-MMTs suggested that a larger content of BODMA-Cl resulted in synthesized adsorbent with a greater adsorption capacity, because neutral BODMA-Cl is predominantly responsible for ion exchange with perchlorate. The maximum adsorption capacity was attained not only by enhanced affinity between BODMA(+) and metallic layer of MMT, but also by increasing density of intercalated BODMA-Cl which is caused by hydrophobic interactions through long alkyl chains and pi-pi interactions through benzene rings among BODMA+/BODMA-Cl. It was also emphasized that the high adsorption capacity of perchlorate on organo-MMTs was achieved with a rapid adsorption rate and stably maintained against variations in temperature, initial solution pH and co-existing competitive anion. (C) 2015 Elsevier B.V. All rights reserved.

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  • Effect of surfactant molecular structure on perchlorate removal by various organo-montmorillonites

    Wuhui Luo, Keiko Sasaki, Tsuyoshi Hirajima

    APPLIED CLAY SCIENCE   114   212 - 220  2015年09月  [査読有り]

     概要を見る

    A series of organo-montmorillonites (organo-Mt) was synthesized using various cationic surfactants with different alkyl-chain lengths, head groups, and alkyl-chain numbers, which were systematically examined for perchlorate adsorption. The products were characterized by the specific surface area, field-emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. In addition, the surfactant loadings and surface charges were investigated by CHN analysis and zeta potential measurements. The greatest adsorption capacity of 0.95 mmol/g-composite was obtained on benzyloctadecyldimethylammonium-modified Mt. Increasing the alkyl-chain length significantly enhanced the capacity and selectivity for perchlorate adsorption, but resulted in decrease of adsorption rate. Compared with trimethylammonium and pyridinium with the same alkyl-chain length, the benzyldimethylammonium as a head group showed better performance in terms of adsorption capacity and selectivity of perchlorate because of higher hydrophobicity. Moreover, increasing the alkyl-chain number decreased adsorption rate, but enhanced adsorption capacity, because of dense packing of alkyl chains and high driving force for entrapment of counter ion-accompanying surfactant. The perchlorate adsorption performance of organo-Mt was synergistically influenced by the alkyl-chain length, head group and alkyl-chain number of the surfactants used for modification. (C) 2015 Elsevier B.V. All rights reserved.

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  • Investigation of the Changes in Hydrogen Bonds During Low-Temperature Pyrolysis of Lignite by Diffuse Reflectance FT-IR Combined with Forms of Water

    Xiangchun Liu, Tsuyoshi Hirajima, Moriyasu Nonaka, Keiko Sasaki

    INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH   54 ( 36 ) 8971 - 8978  2015年09月  [査読有り]

     概要を見る

    The changes in the hydrogen bonds (HBs) of Loy Yang lignite during low-temperature pyrolysis were investigated. The water content of all of the samples was determined by weighing the samples before and after heating in an oven. The changes in the number of the different types of HBs were determined using diffuse reflectance Fourier transform infrared spectroscopy considering the forms of water in lignite. The number of absorption bands, their peak positions, and the area of each peak in each spectrum were determined by curve-fitting analysis with the mixed Gaussian and Lorentzian function. The quantified integrated area of aromatic hydrogen atoms was used to accurately investigate the changes in the HBs. The results showed that the freezable and nonfreezable water contents of the total water weight in raw lignite were 84.8% and 15.2%, respectively. At low temperatures (T &lt;= 100 degrees C), the main removed water was freezable water. The number of OH-lignite interactions decreased compared with raw lignite, which can be attributed to the breaking of bound-water-cluster-lignite HBs. The removal of free water induced a decrease in the number of OH-OH interactions, and then the transition of free water to bound water increased the number of OH-OH interactions. At medium temperatures (100 &lt; T &lt; 200 degrees C), bound and nonfreezable water were mainly removed. The number of OH-lignite and OH-OH interactions changed because of the competition between the transition of bound water to nonfreezable water and desorption of bound and nonfreezable water. At higher temperatures (200 &lt; T &lt;= 250 degrees C), nonfreezable water was the main form of water removed, and carboxyl groups started to drastically pyrolyze. OH-lignite interactions changed as a result of the removal of nonfreezable water and the pyrolysis of carboxyl groups.

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  • Sorption properties of boron on Mg-Al bimetallic oxides calcined at different temperatures

    Sayo Moriyama, Keiko Sasaki, Tsuyoshi Hirajima, Keiko Ideta, Jin Miyawaki

    SEPARATION AND PURIFICATION TECHNOLOGY   152   192 - 199  2015年09月  [査読有り]

     概要を見る

    Mg-Al bimetallic oxides produced via the calcination of hydrotalcite-like compounds ([(Mg0.75Al0.25(OH)(2)](A(n-))(0.75/n)center dot mH(2)O, where A is an anionic species) exhibited high potential for the removal of boron from aqueous solutions. X-ray diffraction patterns for the produced bimetallic oxides revealed that MgO was the primary phase within the range of investigated calcination temperatures. In addition, B-11 NMR spectral analyses indicated that the Mg-Al bimetallic oxides captured trigonal B (B-[3]) and tetrahedral B (B-[4]) after the sorption of boron, regenerating hydrotalcite-like compounds. As the initial concentration of boron increased, the percentage of tetrahedral B-[4] in solid residues after the sorption of boron increased. The B-[4]/B-[3] ratios in the solid residues increased with time along with the regeneration of hydrotalcite-like compounds. Furthermore, the Mg-Al bimetallic oxides produced from hydrotalcite-like compounds were more favorable than other bimetallic oxides and effective than single-phase MgO produced from MgCO3 at the same temperature, indicating that Mg-Al bimetallic oxides are stable materials with the potential for use in the remediation of contaminated sites and water. (C) 2015 Elsevier B.V. All rights reserved.

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    4
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  • Kinetics of nickel extraction from Indonesian saprolitic ore by citric acid leaching under atmospheric pressure

    W. Astuti, T. Hirajima, K. Sasaki, N. Okibe

    Minerals and Metallurgical Processing   32 ( 3 ) 176 - 185  2015年08月  [査読有り]

     概要を見る

    Copyright 2015, Society for Mining, Metallurgy & Exploration Inc. The kinetics of leaching of a saprolitic ore from Indonesia by citric acid solution under atmospheric pressure was investigated. An examination of the effects of leaching temperature, citric acid concentration, pulp density and ore particle size on the dissolution rate of nickel found that they all had significant influence on the rate. The highest nickel recovery (95.6 percent) was achieved under the leaching conditions of ore particle size of 212-355 microns, citric acid concentration of 1 M, leaching time of 15 days, pulp density of 20 weight/volume percent, leaching temperature of 40°C and shaker speed of 200 rpm. The shrinking core model was found to be appropriate for describing the leaching kinetics of this ore in citric acid solutions at atmospheric pressure. The experimental data were well interpreted by this model with rate of reaction controlled by diffusion through the solid product layer. Using the Arrhenius expression, the apparent activation energy for nickel dissolution was evaluated as 12.38 kJ/mol. Finally, on the basis of the shrinking core model, a proposed empirical kinetic model for the leaching of nickel from this Indonesian saprolitic ore was expressed as a mathematical model, which was verified as consistent with the observed experimental results.

  • Biooxidation of Gold-, Silver, and Antimony-Bearing Highly Refractory Polymetallic Sulfide Concentrates, and its Comparison with Abiotic Pretreatment Techniques

    Masahito Tanaka, Yuta Yamaji, Yuken Fukano, Kazuhiko Shimada, Jun Ichiro Ishibashi, Tsuyoshi Hirajima, Keiko Sasaki, Mitsuru Sawada, Naoko Okibe

    Geomicrobiology Journal   32 ( 6 ) 538 - 548  2015年07月  [査読有り]

     概要を見る

    © 2015, Copyright © Taylor & Francis Group, LLC. Effectiveness of different pure and mixed cultures of three moderately thermophilic, extremely acidophilic bacterial strains (Acidimicrobium ferrooxidans ICP, Sulfobacillus sibiricus N1, Acidithiobacillus caldus KU) were investigated for biooxidation of highly refractory polymetallic gold ore concentrates. Despite of its complex mineralogy and the presence of a mixture of potentially inhibitory metals and metalloids, the concentrate was readily dissolved in defined mixed cultures including both iron and sulfur oxidizers, releasing as much as 80% of soluble Fe and 61% of soluble As. Factors to affect microbial mineral dissolution efficiencies (i.e. microbial As(III) oxidation ability, formation of secondary mineral precipitation (e.g. jarosite, elemental sulfur, scorodite, anglesite), and microbial population dynamics during biooxidation) were studied, based on which roles of individual microbes and their synergistic interactions during biooxidation were discussed. Applying the biooxidation pretreatment using the most efficient mixed cultures containing all three strains significantly improved the recovery of both Au (from 1.1% to 86%) and Ag (from 3.2% to 87%). Finally, this study provides one of the very few available comparisons of the effectiveness of different pretreatment techniques for refractory gold ore concentrates: Compared with other abiotic pretreatment approaches (roasting, pressure oxidation, and alkali dissolution), biooxidation was shown to be one of the most effective options in terms of the recovery of Au and Ag.

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  • Sorption of arsenate on MgAl and MgFe layered double hydroxides derived from calcined dolomite

    Mari Yoshida, Paulmanickam Koilraj, Xinhong Qiu, Tsuyoshi Hirajima, Keiko Sasaki

    Journal of Environmental Chemical Engineering   3 ( 3 ) 1614 - 1621  2015年06月  [査読有り]

     概要を見る

    Layered double hydroxides (LDHs) have the property to remove different anions due to their high anion exchange ability. Synthesis of LDHs using natural earth resources is highly desired in environmental concern. Single phases of Mg&lt
    inf&gt
    2.3&lt
    /inf&gt
    Al-, Mg&lt
    inf&gt
    2.9&lt
    /inf&gt
    Al- and Mg&lt
    inf&gt
    4&lt
    /inf&gt
    Fe-LDHs were successfully synthesized from calcined dolomite (CaO·MgO) as Mg source as well as precipitant through optimization of microwave-assisted hydrothermal aging. Sorption data of arsenate over these LDHs were well fitted to non-linear Langmuir adsorption isotherm. Among the materials studied Mg&lt
    inf&gt
    2.3&lt
    /inf&gt
    Al-LDH showed not only superior arsenate sorption capacity but also superior coverage of arsenate. This suggests there are some additional factors other than charge density to influence the sorption density. Mechanism of arsenate sorption was probed by different characterization techniques of solid residues after sorption such as X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transformed infrared, extended X-ray absorption fine structure analysis. Sorption of arsenate over MgAl-LDHs mediated through ion-exchange as well as surface adsorption, depending on charge density of metallic layers. However, sorption of arsenate over MgFe-LDH occurred through ion-exchange along with the formation of inner surface complexes, which leads disturbed layer stacking.

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  • Sorption of H3BO3/B(OH)(4)(-) on calcined LDHs including different divalent metals

    Xinhong Qiu, Keiko Sasaki, Kwadwo Osseo-Asare, Tsuyoshi Hirajima, Keiko Ideta, Jin Miyawaki

    JOURNAL OF COLLOID AND INTERFACE SCIENCE   445   183 - 194  2015年05月  [査読有り]

     概要を見る

    LDHs with different divalent metals (Zn-LDH, Mg-LDH and Ca-LDH) have been synthesized and produced calcined LDHs (Zn-CLDH, Mg-CLDH and Ca-CLDH) for borate removal. Based on XRD, SEM, BET, Al-27 NMR, CO2-TPD, and B-11 NMR, detailed characterization of different CLDHs before and after reaction with the boron species was systematically performed. The surface area, basicity and the particle charge of the different CLDHs, which are related to the hydration and regeneration, were markably influenced by the nature of the divalent metals. Transformation of crystal phases and the types of boron species adsorbed by the different CLDHs varied as time changed. The regeneration of Ca-CLDH required the shortest time. However, Ca-LDH decomposed to release Ca2+ ions, forming ettringite with borate. Zn-CLDH also rapidly transformed into Zn-LDH. During this reconstruction, B(OH)(4)(-) was intercalated into the interlayer of ZnLDHs, which is the predominant mechanism of borate removal by Zn-CLDH. Increase in the initial pH caused a competition between borate and OH- so that the removal efficiency of borate by Zn-CLDH decreased. For Mg-CLDH, surface complexation and electrostatic attraction were included in the first stage, immobilizing boric acid into mg(OH)(2) and attracting borate as interlayer anionic species into the new forming Mg-LDHs in the second stage. (C) 2015 Elsevier Inc. All rights reserved.

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  • Mechanism of boron uptake by hydrocalumite calcined at different temperatures

    Xinhong Qiu, Keiko Sasaki, Yu Takaki, Tsuyoshi Hirajima, Keiko Ideta, Jin Miyawaki

    JOURNAL OF HAZARDOUS MATERIALS   287   268 - 277  2015年04月  [査読有り]

     概要を見る

    Hydrocalumite (Ca-Al-layered double hydroxide (LDH)) was prepared and applied for the removal of borate. The properties of Ca-Al-LDH calcined at different temperatures were diverse, which affected the sorption density and mechanism of boron species. The sorption density increased with increase in calcined temperature and the sample calcined at 900 degrees C (Ca-Al-LDH-900) showed the maximum sorption density in this work. The solid residues after sorption were characterized by B-11 NMR, Al-27 NMR, SEM, and XRD to investigate the sorption mechanism. Dissolution-reprecipitation was the main mechanism for sorption of borate in Ca-Al-LDH. For Ca-Al-LDH calcined at 300 and 500 degrees C, regeneration occurred in a short time and the newly forming LDHs were decomposed to release Ca2+ ions and formed ettringite with borate. Two stages occurred in the sorption of boron by Ca-Al-LDH calcined at 900 degrees C. In the first stage, boron species adsorbed on the alumina gel resulting from the hydration of calcined products. In this stage, borate was included as an interlayer anion into the newly forming LDHs in the following stage, and then immobilized as HBO32- into the interlayer, most the LDHs. (C) 2015 Elsevier B.V. All rights reserved.

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  • Bioreduction and immobilization of hexavalent chromium by the extremely acidophilic Fe(III)-reducing bacterium Acidocella aromatica strain PFBC.

    Yusei Masaki, Tsuyoshi Hirajima, Keiko Sasaki, Naoko Okibe

    Extremophiles : life under extreme conditions   19 ( 2 ) 495 - 503  2015年03月  [査読有り]  [国際誌]

     概要を見る

    The extremely acidophilic, Fe(III)-reducing heterotrophic bacterium Acidocella aromatica strain PFBC was tested for its potential utility in bioreduction of highly toxic heavy metal, hexavalent chromium, Cr(VI). During its aerobic growth on fructose at pH 2.5, 20 µM Cr(VI) was readily reduced to Cr(III), achieving the final Cr(VI) concentration of 0.4 µM (0.02 mg/L), meeting the WHO drinking water guideline of 0.05 mg/L. Despite of the highly inhibitory effect of Cr(VI) on cell growth at higher concentrations, especially at low pH, Cr(VI) reduction activity was readily observed in growth-decoupled cell suspensions under micro-aerobic and anaerobic conditions. Strain PFBC was not capable of anaerobic growth via dissimilatory reduction of Cr(VI), such as reported for Fe(III). In the presence of both Cr(VI) and Fe(III) under micro-aerobic condition, microbial Fe(III) reduction occurred only upon complete disappearance of Cr(VI) by its reduction to Cr(III). Following Cr(VI) reduction, the resultant Cr(III), supposedly present in the form of cationic Cr (III) (OH2) 6 (3+) , was partially immobilized on the negatively charged cell surface through biosorption. When Cr(III) was externally provided, rather than microbially produced, it was poorly immobilized on the cell surface. Cr(VI) reducing ability was reported for the first time in Acidocella sp. in this study, and its potential role in biogeochemical cycling of Cr, as well as its possible utility in Cr(VI) bioremediation, in highly acidic environments/solutions, were discussed.

    DOI PubMed

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  • Rapid Synthesis of LDHs Using Dolomite as a Magnesium Source and Application to Borate Removal

    Xinhong Qiu, Mari Yoshida, Tsuyoshi Hirajima, Keiko Sasaki

    MATERIALS TRANSACTIONS   56 ( 2 ) 224 - 228  2015年02月  [査読有り]

     概要を見る

    A rapid and efficient method based on microwave-assisted treatment has been developed for preparing layered double hydroxides (LDHs) using natural dolomite as a magnesium source. The aging temperature was 120 degrees C and the total synthetic time was only within 6 h. The product was fully characterized by elemental composition, powdery X-ray diffraction, and scanning electron microscopy, to be highly pure hydrotalcite with a flaky shape. The synthesized adsorbent exhibited the sorption capacity of 1.34 mmol/kg which is comparable to boron-specific resin. Based on B-11 MAS NMR and XRD results, the principal mechanism for borate immobilization on the LDHs is ion-exchange followed by transformation of polyborate into monoborate in a process of drying.

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  • Spectroscopic study on the bioleaching of enargite using thermophile

    Sasaki, K.

    Microbiology for Minerals, Metals, Materials and the Environment    2015年

  • バイオテンプレートイオンシーブによる模擬地熱水からのリチウムイオン吸着特性の速度論的および熱力学的評価

    桃木 大地, 余 茜倩, 平島 剛, 笹木 圭子

    Journal of MMIJ   131 ( 7 ) 465 - 469  2015年

     概要を見る

    Atomic hole type of bio-templated lithium ion sieve was synthesized to supply for adsorption of Li+ in simulated geothermal waters at 70<tt>℃</tt>. Sorption data was fit to linearlized Langmuir isotherm and the maximum sorption density was not largely influenced by coexisting ions including larger amounts of Na+ in simulated geothermal waters. The sorption kinetic data was fit to the first order rate, and the kinetic constant was not also influenced by coexisting ions as mentioned above. Temperature elevation accelerated the sorption rate. The activation energy obtained from Arrhenius plots was estimated 4.34 ~ 4.67 kcal/mol, implying that the adsorption is controlled by interparticle diffusion. The enthalpy change was evaluated 2.3 kcal/mol, which is larger than the previously reported value with the atomic hole type of ion sieve. It might be due to the unique morphologies of the present bio-templated ion sieve.

    DOI CiNii

  • Selenium (Se) removal from copper refinery wastewater using a combination of zero-valent iron (ZVI) and Se(VI)-reducing bacterium, thaurea selenatis

    Naoko Okibe, Kiyomasa Sueishi, Mikoto Koga, Yusei Masaki, Tsuyoshi Hirajima, Keiko Sasaki, Shinichi Heguri, Satoshi Asano

    Materials Transactions   56 ( 6 ) 889 - 894  2015年  [査読有り]

     概要を見る

    © 2015 The Japan Institute of Metals and Materials. The copper refinery process produces Se(VI)-bearing wastewater with a high content of Cl- and SO<inf>4</inf>2- ions. To overcome the negative effect caused by Cl- and SO<inf>4</inf>2- ions on Se(VI) reduction and its following removal, this study investigated the possible synergistic effect of the combination of Se(VI)-reducing bacterium, Thaurea (T.) selenatis and zero-valent iron (ZVI). In the presence of SO<inf>4</inf>2- (200mM) and Cl-(300 mM), the following was observed: (i) ZVI alone was unable to remove Se both under strictly aerobic and micro-aerobic conditions. (ii) Se(VI) reduction by T. selenatis alone was severely inhibited under anaerobic conditions (and thus no microbial growth was observed). (iii) On the other hand, T. selenatis was capable of growth and Se(VI) reduction under micro-aerobic conditions. (iv) Combining T. selenatis and ZVI under micro-aerobic conditions showed a synergistic effect on Se(VI) reduction, readily facilitating Se removal. This synergistic effect was optimized by adjusting the pH to near neutral (optimal for T. selenatis growth), but by adjusting the temperature to 35°C (sub-optimal for T. selenatis growth): Se removal of 55% by T. selenatis alone, was significantly improved to 98% by combining T. selenatis and ZVI. The proposed key process to display the synergistic effect on Se removal under micro-aerobic conditions is as follows: (i) Using the remaining dissolved O<inf>2</inf> (DO) during the first hours, T. selenatis can overcome the inhibitory effect of Cl- and SO<inf>4</inf>2- by growing with more energy-gaining aerobic respiration, (ii) ZVI indirectly serves as a reducing agent to maintain low DO levels, consequently readily switching from aerobic to anaerobic Se(VI) respiration by T. selenatis. (iii) ZVI may also be acting directly for Se deposition by reducing microbially-produced intermediate Se(IV), which is more reactive than original Se(VI). The present findings could be used as a basis for developing an economically feasible and environmentally harmless bio-treatment technology for Se(VI) containing copper refinery wastewaters.

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  • Synthesis of a Biotemplated Lithium Ion-Sieve Derived from Fungally Formed Birnessite

    Keiko Sasaki, Qianqian Yu

    ADVANCES IN THE ENVIRONMENTAL BIOGEOCHEMISTRY OF MANGANESE OXIDES   1197   169 - 183  2015年  [査読有り]

     概要を見る

    Biogenic birnessite is a stable form of manganese oxide found in nature that originates from microbial oxidation. Its unique structural properties provide potential for materials scientists to fabricate new functionalized materials. This study used a manganese-oxidizing fungus, Paraconiothyrium sp. WL-2, as a bio-oxidizer and biotemplate to prepare a lithium ion-sieve in the shape of a microtube through a solid-state transformation by calcination. The effect of calcination temperature was studied in terms of chemical composition, structure, and morphology. The results showed that the calcination temperature affects not only the weight fraction but also the crystallinity of the lithium manganese oxide spinel, which significantly influences the adsorption capacity of lithium ions.

  • In situ X-ray diffraction investigation of the evolution of a nanocrystalline lithium-ion sieve from biogenic manganese oxide

    Qianqian Yu, Keiko Sasaki

    HYDROMETALLURGY   150   253 - 258  2014年12月  [査読有り]

     概要を見る

    Microbial catalysis, a primary pathway for the generation of Mn oxides in most natural environments, provides potential to fabricate new materials. A microtube-type lithium manganese oxide (LMO-MT) was synthesized through a solid-state transformation using Mn-oxidizing fungus, Paraconiothyrium sp. WL-2. Compared with abiotic precursors, the lithium-ion sieve microtube (HMO-MT) showed better performance for Li+ recovery. In order to clarify the formation process of LMO-MTs, in situ high-temperature X-ray diffraction was used to compare with three synthetic references. The effects of calcination temperature on crystal phase, composition, particle size and lattice parameters of the LMO-MTs were systematically discussed. It was found that the poorly crystalline structure of biogenic precursor as well as high content of organic matter facilitated the formation of highly crystalline LMO-MTs at low temperature. The unique structural properties of LMO-MTs, including high crystallinity and small lattice constant, are attributed to the high Li+ sorption capacity of HMO-MTs. (c) 2014 Elsevier B.V. All rights reserved.

    DOI

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  • Selective flotation of chalcopyrite and molybdenite with plasma pre-treatment

    Tsuyoshi Hirajima, Masanori Mori, Osamu Ichikawa, Keiko Sasaki, Hajime Miki, Mohsen Farahat, Mitsuru Sawada

    MINERALS ENGINEERING   66-68   102 - 111  2014年11月  [査読有り]

     概要を見る

    For pretreatment of selective flotation, plasma treatment of chalcopyrite and molybdenite was applied then the minerals were washed by solution at pH 9 with oxygen bubbling. Surface characteristics of these minerals were investigated with AFM, XPS, zeta potential and contact angle measurements. Contact angle of chalcopyrite and molybdenite decreased a lot by plasma treatment. When they were washed with pH 9 solution with oxygen bubbling, contact angle of molybdenite increased whereas chalcopyrite one kept low. Adhesion force measurements indicated similar behavior. Result of flotation experiments indicated low recovery of both chalcopyrite and molybdenite after plasma treatment and only molybdenite recovery became higher after washing. Selective flotation of chalcopyrite and molybdenite could be achieved with this process. However, flotation of mixture of chalcopyrite and molybdenite after these treatments indicated both chalcopyrite and molybdenite were depressed. Addition of emulsified kerosene changed the flotation results where molybdenite was floated and chalcopyrite was depressed. Possible mechanism of selective flotation was proposed from the results of XPS, AFM, etc. (C) 2014 Elsevier Ltd. All rights reserved.

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  • Adsorption characteristics of Cs+ on biogenic birnessite

    Keiko Sasaki, Qianqian Yu, Taichi Momoki, Takuya Kaseyama

    APPLIED CLAY SCIENCE   101   23 - 29  2014年11月  [査読有り]

     概要を見る

    Adsorption of Cs+ on biogenic birnessite was investigated and compared with (ad)sorption of other heavy metals and also with (ad)sorption on chemically synthesized birnessite. The adsorption density of Cs+ on biogenic birnessite was smaller than that on chemically synthesized birnessite; however, the (ad)sorption densities of Co2+ and Ni2+ on biogenic birnessite were larger than on chemically synthesized birnessite. These phenomena can be interpreted by considering the distinctive nano-structure of biogenic birnessite, which is not only poorly crystalline and includes organic matter but also according to EXAFS contains a greater proportion of vacant central metal sites than is found in synthetic birnessite. Adsorbed Cs+ ions on both birnessites were mainly in the form of outer sphere complexes, which cannot easily occupy vacant central metal sites in biogenic birnessite. Biogenic birnessite has a greater specific surface area and more fine pores than synthetic birnessite, but these factors do not necessarily lead to more adsorption sites for Cs+ ions. (C) 2014 Elsevier B.V. All rights reserved.

    DOI

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  • Screening micro-organisms for cadmium absorption from aqueous solution and cadmium absorption properties of Arthrobacter nicotianae

    Takehiko Tsuruta, Daishi Umenai, Tomonobu Hatano, Tsuyoshi Hirajima, Keiko Sasaki

    BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY   78 ( 10 ) 1791 - 1796  2014年10月  [査読有り]

     概要を見る

    To obtain basic information on how microbial cells absorb cadmium from aqueous solution, we examined cadmium absorption in various micro-organisms. Of 51 micro-organism strains tested, we found that some Gram-positive bacteria, such as, Arthrobacter nicotianae and Bacillus subtilis, and some actinomycetes, such as, Streptomyces flavoviridis and S. levoris were highly capable of absorbing cadmium from an aqueous solution. A. nicotianae absorbed the largest amount of cadmium, over 800 mu mol cadmium per gram of dry wt. cells. However, cadmium absorption by A. nicotianae was affected by the solution pH, cadmium concentration, and cell density. The absorption of cadmium was very rapid. Some factors that affected cadmium absorption by A. nicotianae cells were also discussed.

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  • Immobilization of Sr2+ on naturally derived hydroxyapatite by calcination of different species of fish bones and influence of calcination on ion-exchange efficiency

    Keiko Sasaki, Tomoyo Goto

    CERAMICS INTERNATIONAL   40 ( 8 ) 11649 - 11656  2014年09月  [査読有り]

     概要を見る

    Animal bones are waste materials that can be developed as effective ionic exchangers after appropriate calcination treatment. Calcination of fish bones improves the crystallinity and purity of hydroxyapatite (HAp), but is sometimes accompanied with the formation of by-products and changes in the lattice parameters of HAp. In the present study, naturally derived HAp was obtained by calcination of fish bones that had different impurity contents, and the influence of calcination on the Sr2+ ion-exchange efficiency of the resulting HAp materials was investigated. Calcination of natural fish bones with high Mg contents led to the formation of beta-tricalcium phosphate, which did not contribute to the sorption of Sr2+, and those with high carbonate contents led to the formation of CaO, which increased the solution pH, thus facilitating ion-exchange with Sr2+. The specific surface area of the calcined fish bones played a trivial role in the sorption densities of Sr2+. Fish bones calcined at 1000 degrees C displayed a smaller HAp a-lattice when compared with the theoretical a-lattice parameter because of decarbonation. High Sr2+ sorption densities were obtained with natural HAp containing low Mg and high CO32- contents. This finding is practically useful to apply natural animal bones to sorbents in groundwater remediation. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

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  • Effects of trace elements in fish bones on crystal characteristics of hydroxyapatite obtained by calcination

    Tomoyo Goto, Keiko Sasaki

    CERAMICS INTERNATIONAL   40 ( 7 ) 10777 - 10785  2014年08月  [査読有り]

     概要を見る

    Hydroxyapatite (HAp) which has ion-exchange properties is a useful sorbent for heavy metals and radionuclides. Ion-exchange capacity is influenced by the composition and crystallinity of HAp. In this study, synthesis of HAp from calcined fish bones was investigated, focusing on the effects of major trace elements. The HAp formed by calcination of fish bones is most likely B-type carbonated HAp. Even when we include the Na, K and Mg contents, the molar ratio of (Ca+ substituted cation)/P of fish bones was about similar to 5% lower than the theoretical one (Ca/P=1.67). X-ray diffraction and EXAFS analysis results indicated that the crystallinity of Horse mackerel bones (Hm) is the lowest. Calcined Hm had the highest Mg content, accompanied with the formation of beta-tricalcium phosphate and the least crystalline HAp of the fish bones studied. In calcination of Tuna bones (Tn), which had a high Ca/P ratio and low Mg content, highly crystalline HAp and calcium oxide were formed at temperatures above 800 degrees C. The findings are useful for application of calcined fish bones as green materials for water remediation, because these factors strongly affect the efficiency of ion exchange in HAp and the pH changes in solutions after HAp immersion. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

    DOI

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    73
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  • THE HOT COMPRESSED WATER TREATMENT OF SOLID WASTE MATERIAL FROM THE SUGAR INDUSTRY FOR VALUABLE CHEMICAL PRODUCTION

    Dewi Agustina Iryani, Satoshi Kumagai, Moriyasu Nonaka, Yoshinobu Nagashima, Keiko Sasaki, Tsuyoshi Hirajima

    INTERNATIONAL JOURNAL OF GREEN ENERGY   11 ( 6 ) 577 - 588  2014年07月  [査読有り]

     概要を見る

    Sugarcane bagasse, the solid waste material produced in the sugar industry, was subjected to treatment in hot compressed water. The experiments were performed in a batch-type reactor containing slurry of 10 ml of water and 1.2 g of solids. The reactor was heated to temperatures ranging between 200 degrees C and 300 degrees C for reaction times of 3 to 30 min. The product was separated into liquid and solid fractions. Each fraction was analyzed to investigate the alteration of the main lignocellulosic polymers by hot compressed water. Results for the liquid fractions showed that increased temperatures and reaction times completely dissolved hemicellulose and cellulose in the water, leaving lignin in the solid product. During treatment, hemicellulose and cellulose gradually decomposed into simple sugars, which were then degraded and decomposed into furfural, 5-(hydroxymethyl)furfural (5-HMF) and organic acids. However, the yield of furans and some organic acids decreased and became undetectable at 300 degrees C and with increasing reaction time. The solid fraction was also characterized before and after treatment. Results showed that the hydrogen and oxygen content of the solids decreased with increased reaction conditions, due to dehydration and decarboxylation reactions. The reactions also increased the carbon content of the treatment products by 1.2-1.6 times that in the raw material, suggesting that the hot compressed water treatment of sugarcane bagasse can be considered for the provision of valuable chemicals for biofuel and high-carbon-content material (biochar).

    DOI

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    19
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  • Geochemical Evaluation of Arsenic and Manganese in Shallow Groundwater and Core Sediment in Singair Upazila, Central Bangladesh

    M. A. Halim, Ratan K. Majumder, G. Rasul, Y. Hirosiro, K. Sasaki, J. Shimada, K. Jinno

    ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING   39 ( 7 ) 5585 - 5601  2014年07月  [査読有り]

     概要を見る

    Geochemical characteristics of shallow groundwaters and core sediments are studied to better understand the sources and transportation process responsible for As and Mn enrichment in Singair Upazila of Manikgonj District in Bangladesh. Results demonstrate that the groundwater is mostly of Ca-HCO3 and Ca-Mg-HCO3 types. Concentrations of As in groundwater ranged from 1 to 159 mu g/L, with about 59% of these exceeded the WHO drinking water guideline of 10 mg/L. In addition, all groundwater samples had higher concentrations of Mn (0.6-5.7 mg/L) and Fe (0.9-16.5 mg/L) than the WHO drinking water guidelines (0.4 and 0.3 mu g/L, respectively). Most groundwaters contained both As(III) and As(V) species in which the concentration of As(III) was generally higher than that of As(V). High concentration of As (23 mg/kg) with elevated levels of FeO, MnO and TOC were found within the upper 15 m of silty clay sediments. Multivariate geostatistical analysis showed that dissolution of the Fe-Mn oxides was the dominant process of As and Mn release in groundwater. Geochemical modeling suggested that the concentrations of As, Mn, Fe and PO43- in groundwaters were also influenced by secondary minerals phases in addition to redox processes.

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    18
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  • Speciation of arsenic in a thermoacidophilic iron-oxidizing archaeon, Acidianus brierleyi, and its culture medium by inductively coupled plasma-optical emission spectroscopy combined with flow injection pretreatment using an anion-exchange mini-column.

    Naoki Higashidani, Takashi Kaneta, Nobuyuki Takeyasu, Shoji Motomizu, Naoko Okibe, Keiko Sasaki

    Talanta   122   240 - 5  2014年05月  [査読有り]  [国際誌]

     概要を見る

    The thermoacidophilic iron-oxidizing archaeon Acidianus brierleyi is a microorganism that could be useful in the removal of inorganic As from wastewater, because it simultaneously oxidizes As(III) and Fe(II) to As(V) and Fe(III) in an acidic culture medium, resulting in the immobilization of As(V) as FeAsO₄. To investigate the oxidation mechanism, speciation of the As species in both the cells and its culture media is an important issue. Here we describe the successive determination of As(III), As(V), and total As in A. brierleyi and its culture medium via a facile method based on inductively coupled plasma-optical emission spectroscopy (ICP-OES) with a flow injection pretreatment system using a mini-column packed with an anion-exchange resin. The flow-injection pretreatment system consisted of a syringe pump, a selection valve, and a switching valve, which were controlled by a personal computer. Sample solutions with the pH adjusted to 5 were flowed into the mini-column to retain the anionic As(V), whereas As(III) was introduced into ICP-OES with no adsorption on the mini-column due to its electrically neutral form. An acidic solution (1 M HNO₃) was then flowed into the mini-column to elute As(V) followed by ICP-OES measurement. The same sample was also subjected to ICP-OES without being passed through the mini-column in order to determine the total amounts of As(III) and As(V). The method was verified by comparing the results of the total As with the sum of As(III) and As(V). The calibration curves showed good linearity with limits of detection of 158, 86, and 211 ppb for As(III), As(V), and total As, respectively. The method was successfully applicable to the determination of the As species contained in the pellets of A. brierleyi and their culture media. The results suggested that the oxidation of As(III) was influenced by the presence of Fe(II) in the culture medium, i.e., Fe(II) enhanced the oxidation of As(III) in A. brierleyi. In addition, we found that no soluble As species was contained in the cell pellets and more than 60% of the As(III) in the culture medium was oxidized by A. brierleyi after a 6-day incubation.

    DOI PubMed

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    9
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  • Synthesis of biogenic Mn oxide and its engineering application to Li ion sieve

    Keiko Sasaki, Qianqian Yu

    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY   247  2014年03月  [査読有り]

  • Contribution of boron-specific resins containing N-methylglucamine groups to immobilization of borate/boric acid in a permeable reactive barrier comprising agglomerated MgO

    Keiko Sasaki, Xinhong Qiu, Jin Miyawaki, Keiko Ideta, Hitoshi Takamori, Sayo Moriyama, Tsuyoshi Hirajima

    DESALINATION   337   109 - 116  2014年03月  [査読有り]

     概要を見る

    Permeable reactive barrier (PRB) column tests for removal of borate were carried out over 287 days corresponding to 76 pore volumes (pv), using MgO agglomerates as the primary reactive material, with and without boron-specific resin (CRB05). Adding 3 (% v/v) CRB05 increased the column shelf life (the time until effluent contains the maximum boron concentration for drinking water) by about 50%, and increased boron accumulation within the column by 15% over 76 pv. The quantities of boron captured were 15-17 mg/g-CRB05, and 1-2 mg-B/g-MgO, decreasing with increasing distance along the column. Rietveld refinement of X-ray diffraction patterns from solid residues after 76 pv revealed that 69-78% of the MgO was transformed into Mg(OH)(2) independent of distance along the column, implying that hydration of MgO is not always associated with integration of borate. B-11-NMR spectra demonstrated that trigonal B (B-[3]) is predominantly immobilized in Mg(OH)(2) in both columns, while tetragonal B (B-[4]) is largely trapped in the added CRB05. The complexed forms of B-[4] with the N-methylglucamine group after 76 pv were mostly bischelate, with some monodentate. CRB05 contributed to immobilization of B-[4] (which is difficult to react with MgO), however, the resin surface was gradually covered with Mg(OH)(2) and inactivated. (C) 2013 Elsevier B.V. All rights reserved.

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    11
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  • Microbial formation of crystalline scorodite for treatment of As(III)-bearing copper refinery process solution using Acidianus brierleyi

    Naoko Okibe, Masaharu Koga, Shiori Morishita, Masahito Tanaka, Shinichi Heguri, Satoshi Asano, Keiko Sasaki, Tsuyoshi Hirajima

    Hydrometallurgy   143   34 - 41  2014年03月  [査読有り]

     概要を見る

    Scorodite (FeAsO4·2H2O) is a thermodynamically stable mineral with advantages as an arsenic disposal compound. With an aim to immobilize highly toxic As(III) contained in the copper refinery process solution, eventually in the form of crystalline scorodite, the use of thermo-acidophilic iron-oxidizing archaeon, Acidianus brierleyi, was investigated. The extent of As(III) oxidation by Ac. brierleyi became greater at elevated culture As(III) concentrations, especially in the presence of yeast extract. Microbial growth on yeast extract was also implied to facilitate As(III) oxidation by Fe(III) on cell surface. When the initial Fe(II)/As(III) ratio was set at 1.4 in the presence of yeast extract, both ions were readily oxidized and 86-100% of As was precipitated as crystalline scorodite. The molar ratio of microbially-oxidized Fe(II) and As(III) was an important factor to determine the type of the secondary mineral formed. Phosphate concentration was another critical factor for scorodite biomineralization. Biogenic scorodite was crystallized with almond-shaped polyhedron habit of 1 μm in size. This study demonstrates the applicability of a one-step bioprocess which enables treatment of As(III)-bearing copper refinery process solution by producing biogenic crystalline scorodite. © 2014 Elsevier B.V.

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    49
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  • Sorption of borate onto layered double hydroxides assembled on filter paper through in situ hydrothermal crystallization

    Xinhong Qiu, Keiko Sasaki, Tsuyoshi Hirajima, Keiko Ideta, Jin Miyawald

    APPLIED CLAY SCIENCE   88-89   134 - 143  2014年02月  [査読有り]

     概要を見る

    Boric acid is known to be difficult to immobilize because it has a pK(a) of 9.23, which means it is present in a molecular form in most aqueous environments and can be changed in the structure and nature with the change of the environmental conditions. Layered double hydroxides (LDHs) are potential sorbents for borate. However, the drawbacks of using LDHs for borate removal are that they are affected by the presence of other anions and are difficult to separate from water. In the present work, novel composites of Mg-Al type of LDH, synthesized onto filter papers and then intercalated with gluconate (F-LDH-G) were prepared. LDH with interlayer of carbonate form was first immobilized onto the surface of filter paper (F-LDH-CO3) by in situ hydrothermal crystallization, and then ion-exchanged sequentially with chloride (F-LDH-Cl) followed by gluconate. The influence of the molar ratio of gluconate/LDH and reaction time on F-LDH-G synthesis was explored. Products were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and nuclear magnetic resonance as well as measurements of borate sorption. The optimal molar ratio of gluconate/LDH and reaction time for preparing F-LDH-G from F-LDH-Cl were 40 and 24 h (F-LDH-G-40-24 h), respectively. F-LDH-G-40-24 h had higher sorption density and greater stability than both the original filter paper and the filter papers containing other LDHs, even in the presence of other anions. B-11 NMR and XRD results indicate that the principal mechanism for borate immobilization on F-LDH-G-40-24 h is complexation of gluconate with borate in both bischelate and monodentate forms. The novel composite is boron-specific and facilitates solid/liquid separation. (C) 2013 Elsevier B.V. All rights reserved.

    DOI

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    6
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  • One-step synthesis of layered double hydroxide-intercalated gluconate for removal of borate

    Xinhong Qiu, Keiko Sasaki, Tsuyoshi Hirajima, Keiko Ideta, Jin Miyawaki

    SEPARATION AND PURIFICATION TECHNOLOGY   123   114 - 123  2014年02月  [査読有り]

     概要を見る

    The sorption of borate by ion exchange using a traditional layered double hydroxide (LDH) is affected by external conditions such as coexisting anions. Hydrotalcite intercalated with d-gluconate (G-LDH) was synthesized through a one-step microwave-assisted treatment and characterized by XRD, TEM, FTIR, TG/DTA and two-dimensional B-11 NMR. Several factors that influence sorption of borate were investigated: gluconate content in the LDH, G-LDH dosage, coexisting anions, initial pH of borate solution and sorption temperature. The synthesized adsorbent exhibited a greater borate sorption rate than the traditional hydrotalcite (NO3-LDH) or a boron-specific resin. The maximum sorption capacity was 1.27 mmol/g (obtained by fitting to the Langmuir model). The G-LDH sorption density increased with increasing initial borate concentration and adsorbent dosage. In the presence of 50 mM sulfate, sorption of borate by NO3-LDH significantly decreased and no obvious sorption could be observed, whereas the sorption of borate by G-LDH was maintained at similar to 0.57 mmol/g. B-11 NMR indicated that the sorption mechanism of borate by G-LDH is mainly through bischelate and monodentate types of complexation with borate. This mechanism is similar to that of CRB05, and fundamentally different from that of NO3-LDH. (C) 2014 Elsevier B.V. All rights reserved.

    DOI

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    25
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  • Selective flotation of chalcopyrite and molybdenite by surface oxidation

    Tsuyoshi Hirajima, Masanori Mori, Osamu Ichikawa, Keiko Sasaki, Hajime Miki, Mitsuru Sawada

    IMPC 2014 - 27th International Mineral Processing Congress    2014年

     概要を見る

    For pretreatment of selective flotation, surface oxidation of chalcopyrite and molybdenite was applied by oxygen plasma then the minerals were washed by solution at pH 9 with oxygen bubbling. Surface characteristics of these minerals were investigated with AFM, XPS, zeta potential and contact angle measurements. Contact angle of chalcopyrite and molybdenite decreased a lot by plasma treatment. When they were washed with pH 9 solution with oxygen bubbling, contact angle of molybdenite increased whereas chalcopyrite one kept low. Adhesion force measurements indicated similar behavior. Result of flotation experiments indicated low recovery of both chalcopyrite and molybdenite after plasma treatment and only molybdenite recovery became higher after washing. Selective flotation of chalcopyrite and molybdenite could be achieved with this process. Possible mechanism of selective flotation was proposed from the results of XPS, AFM, etc.

  • Separation mechanism of tennantite and chalcopyrite with flotation after oxidation using oxygen

    Himawan. T. B. M. Petrus, Tsuyoshi Hirajima, Keiko Sasaki, Hideyuki Okamoto

    IMPC 2014 - 27th International Mineral Processing Congress    2014年

     概要を見る

    Flotation of arseno bearing minerals from their copper ore has been an interest due to the increasing awareness on protecting the environment by minimizing the possibility of exposed arsenic compound. Some approaches have been proposed, but the mechanisms of separations have not yet fully understood. In this study, oxidation using oxygen was applied. Instead of the complex copper ore flotation results, pure single mineral of tennantite and chalcopyrite foatability was conducted using Hallimond tube. Resembled with the flotation results of copper concentrate containing tennantite, the separation possessed the best result at alkaline condition (pH 11) at where the arsenic content was reduced from 3300 ppm to 1800 ppm. In order to be able to understand the mechanism of the separation atomic force microscope (AFM) was utilized. AFM images showed changes in morphology and behavior when minerals were treated in both acid and alkaline condition. It was found that the morphological change showed the reaction products representing the rate of reactivity of tennantite and chalcopyrite. From the measured force of adhesion, it can be observed that in alkaline condition the surface of both minerals is more hydrophilic than that in acidic condition possessing higher value. This is in accordance with the X-ray photoelectron spectroscopy (XPS) spectra in which hydroxide moieties occupied the mineral surface in alkaline condition while elemental sulfur is in acidic condition.

  • A4 Synthesis of surfactant-modified montmorillonites and their evaluations for removal of perchlorate

    Luo Wuhui, Sasaki Keiko, Hirajima Tsuyoshi

    粘土科学討論会発表論文抄録   58   37 - 37  2014年

    DOI CiNii

  • 水酸化マグネシウム共沈法における廃水中のホウ素除去機構の考察

    井澤 彩, 前田 素生, 所 千晴, 笹木 圭子

    Journal of MMIJ   130 ( 5 ) 155 - 161  2014年  [査読有り]

     概要を見る

    We investigated co-precipitation using magnesium (Mg) salt as a cost efficient method of removing B from wastewater. To clarify the mechanism of co-precipitation and the effect of precipitation rate against B sorption mechanism, we conducted co-precipitation experiments changing reaction time at different temperatures. For these experiments, we carried out sorption isotherm formation and XRD analysis to clarify how co-precipitation of B with magnesium hydroxide (Mg (OH) 2) occurred. The sorption isotherm of co-precipitation was a BET type, while the XRD peak shift occurred as the initial B/Mg molar ratio increased. These results suggested that the mechanism of B uptake was a combination of surface precipitation and surface complexation, and the later mechanism became more apparent as the initial B/Mg molar ratio increased. XRD spectrum of co-precipitated residues was relatively similar to that of hydromagnesite, which indicated that structure of surface precipitation is similar to that of hydromagnesite. Co-precipitation experiments for 6 hours revealed that Mg precipitation rate was faster at the higher temperature, while sorption density became worse as the temperature increased. At 40<tt>℃</tt> and 60<tt>℃</tt>, XRD peak shift did not occur when the initial B/Mg molar ratio was0.063, which suggests that fast precipitation rate disturbed production of surface precipitation. In addition, the initial B/Mg molar ratio in which B sorption mechanism changed from formation of surface compexation to production of surface precipitation became larger as Mg precipitation rate increased.

    DOI CiNii

  • Effect of calcination temperature on Mg-Al bimetallic oxides as sorbents for the removal of F- in aqueous solutions

    Sayo Moriyama, Keiko Sasaki, Tsuyoshi Hirajima

    CHEMOSPHERE   95   597 - 603  2014年01月  [査読有り]

     概要を見る

    Bimetallic oxides were synthesized from hydrotalcite using increasing calcination temperatures (873, 1073,1273 K). These bimetallic oxides were fully characterized and the sorption density of F- was investigated. X-ray diffraction patterns for the produced bimetallic oxides showed that MgO was the primary phase within the range of investigated calcination temperatures, but MgO crystallinity increased with calcination temperature and an additional MgAl2O4 phase was formed. In the process of F- sorption, the bimetallic oxides were primarily transformed into hydrotalcite with intercalation of F-.
    The Higher calcination temperature increased the MgAl2O4 phase, which did not contribute to the immobilization of F-. These findings show that optimizing the calcination temperature can be used to maximize the sorption density of this material for F- removal. (C) 2013 Elsevier Ltd. All rights reserved.

    DOI

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  • Effect of calcination temperature for magnesite on interaction of MgO-rich phases with boric acid

    Keiko Sasaki, Sayo Moriyama

    CERAMICS INTERNATIONAL   40 ( 1 ) 1651 - 1660  2014年01月  [査読有り]

     概要を見る

    Magnesia (MgO), which can be obtained by calcination of natural magnesite, is one of the most effective known sorbents for borate in aqueous solutions. Here we examine the effect of calcination temperature on sorption of borate for MgO-rich phases produced by calcination of magnesite at 873-1373 K. Calcination at or above 1273 K produced a single magnesium oxide phase, whereas basic magnesium carbonates (mMgCO(3)center dot nMg(OH)(2)center dot xH(2)O) formed in association with magnesium oxide at or below 1073 K. Calcination temperature directly affected the efficiency of decarbonation of magnesium carbonate, and the solubility and basicity of magnesium oxide in the resultant calcined products. These factors (along with the boron concentration) essentially control the immobilization mechanism of borate on the calcined MgO-rich phases. After sorption of borate on products calcined at lower temperatures, different types of basic magnesium carbonates were formed that are less effective at immobilizing borate. At low borate concentrations, under saturation for magnesium borate hydrate (Mg7B4O13 center dot 7H(2)O), co-precipitation of borate with Mg(OH)(2) predominates. However, as magnesium borate hydrate becomes supersaturated, both precipitation of Mg7B4O13 center dot 7H(2)O and co-precipitation with Mg(OH)(2) contribute significantly to borate immobilization. Calcination temperature is a key practical factor affecting the borate sorption efficiency by changing the immobilization mechanism. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

    DOI

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    29
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  • Mobility and impact of trace metals in Barapukuria coal mining area, Northwest Bangladesh

    M. A. Halim, R. K. Majumder, M. N. Zaman, S. Hossain, M. G. Rasul, K. Sasaki

    ARABIAN JOURNAL OF GEOSCIENCES   6 ( 12 ) 4593 - 4605  2013年12月  [査読有り]

     概要を見る

    Trace metals were analyzed in water and sediment samples from Barapukuria coal mine area of Bangladesh in order to evaluate their mobility and possible environment consequences. Cadmium is the most mobile element with an average partition coefficient (log K (d) ) of 2.95 L/kg, while V is the least mobile element with a mean log K (d) of 5.50 L/kg, and their order of increasing mobility is: V &lt; As &lt; Pb &lt; Fe &lt; Cr &lt; Se &lt; Mn &lt; Ni &lt; Zn &lt; Cu &lt; Ba &lt; Sr &lt; Cd. Contents of organic carbon in sediment samples shows strong positive correlations with most trace metals as revealed by the multivariate geostatistical analysis. The overall variation in concentration is mainly attributed to the discharge of effluents originating from the coal mining activities around the study area. Compared to their background, Ni and Cu are the most enriched while significant enrichment of As, Mn, Ba, Sr, Cr, and Pb is also observed in the sediments. Geoaccumulation indices (I (geo) ) suggest sediments are moderately to heavily polluted with respect to Ni and Cu. The metal pollution index (MPI) varied from 91.91 to 212.01 and the highest value is found at site CM03 that is close to discharge point. The sediment quality guideline index (SQG-I (Intervention) ) values (0.56-1.52) suggest that the sediments at the study area have moderate to high ecotoxicological risk.

    DOI

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    25
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  • Bio-templated synthesis of lithium manganese oxide microtubes and their application in Li+ recovery

    Qianqian Yu, Keiko Sasaki, Tsuyoshi Hirajima

    Journal of Hazardous Materials   262   38 - 47  2013年11月  [査読有り]

     概要を見る

    Microbial transformations, a primary pathway for the Mn oxides formation in nature, provide potential for material-oriented researchers to fabricate new materials. Using Mn oxidizing fungus Paraconiothyrium sp. WL-2 as a bio-oxidizer as well as a bio-template, a special lithium ion sieve with microtube morphology was prepared through a solid-state transformation. Varying the calcination temperature from 300 to 700°C was found to influence sample properties and consequently, the adsorption of Li+. Lithium manganese oxide microtube (LMO-MTs) calcined at different temperatures as well as their delithiated products (HMO-MTs) were characterized by X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Calcination temperatures affect not only the content but also the crystal structure of LMO spinel, which is important in Li+ adsorption. The optimized sample was obtained after calcination at 500°C for 4h, which shows higher Li+ adsorption capacity than particulate materials. © 2013 Elsevier B.V.

    DOI PubMed

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    40
    被引用数
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  • Cobalt(II) Oxidation by Biogenic Mn Oxide Produced by Pseudomonas sp. Strain NGY-1

    Kazuya Tanaka, Qianqian Yu, Keiko Sasaki, Toshihiko Ohnuki

    Geomicrobiology Journal   30 ( 10 ) 874 - 885  2013年11月  [査読有り]

     概要を見る

    Oxidation of Co by Mn oxide has been investigated using abiotically synthesized Mn oxide. However, oxidation of Co by biogenic Mn oxide is not well known. In this study, we isolated a Mn-oxidizing bacterium (Pseudomonas sp.), designated as strain NGY-1, from stream water. Sorption experiments on Co were carried out using biogenic Mn oxide produced by strain NGY-1. Similar sorption experiments were also conducted using a synthetic analogue of δ-MnO2. Sorption of Co on δ-MnO2 was faster and stronger than that on biogenic Mn oxide, which was possibly due to their structural difference and/or the presence of bacterial cells in biogenic Mn oxide. X-ray absorption near-edge structure spectra clearly demonstrated that Co was oxidized from the divalent to the trivalent state on biogenic Mn and δ-MnO2. The oxidation property of both the biogenic Mn oxide and δ-MnO2 was stronger under circumneutral conditions than under acidic conditions. Linear combination fitting using divalent and trivalent Co reference materials suggested that ∼90% of Co was oxidized at pH ∼ 6, whereas ∼80% was oxidized at pH ∼ 3. Oxidation properties of the biogenic Mn oxide and δ-MnO2 were similar, but Co(II) oxidation by biogenic Mn oxide was slower than that by δ-MnO2. The difference of Co oxidation may be caused by the coexisting bacterial cells or structural differences in the Mn oxides. Supplemental materials are available for this article. Go to the publisher's online edition of Geomicrobiology Journal to view the supplemental file. © 2013 Copyright Taylor and Francis Group, LLC.

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    20
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  • Zinc Sorption During Bio-oxidation and Precipitation of Manganese Modifies the Layer Stacking of Biogenic Birnessite

    Qianqian Yu, Keiko Sasaki, Kazuya Tanaka, Toshihiko Ohnuki, Tsuyoshi Hirajima

    GEOMICROBIOLOGY JOURNAL   30 ( 9 ) 829 - 839  2013年10月  [査読有り]

     概要を見る

    The formation and structural evolution of fungal mediate biogenic birnessite are dynamic processes. Although the associations of Zn with the pre-formed biogenic Mn oxides are relatively well understood, the reactivity of the intermediate precipitate at the initial stage of Mn bio-oxidation appears to differ from the final precipitate. In the present work, Zn sorption during precipitation of biogenic Mn oxides was investigated contrasting Zn sorption to pre-formed biogenic Mn oxides, using the Mn-oxidizing fungus Paraconiothyrium sp. WL-2. A substantially higher Zn uptake was found during precipitation of biogenic Mn oxides compared to Zn sorption to pre-formed biogenic Mn oxides. The presence of Zn during Mn oxidation resulted in a biogenic Mn oxide with reduced ordering in the c-axis. The precipitate was identified by X-ray diffraction (XRD) as a layer-type Mn oxide with structural properties similar to hexagonal birnessite. Extended X-ray absorption fine structure (EXAFS) spectroscopy showed that Zn forms triple-corner-sharing tetrahedral coordination ((TCS)-T-IV-Zn) complexes on the surface of birnessite, which may inhibited layer stacking of birnessite in the final products. This study emphasizes the importance of the intermediate precipitates on Zn sorption, and provides insight regarding the dynamic interaction between Zn and Mn oxide in the process of microbiological oxidation. Supplemental materials are available for this article. Go to the publisher's online edition of Geomicrobiology Journal to view the supplemental file.

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  • Mn(II)-Oxidizing Activity of Pseudomonas sp Strain MM1 is Involved in the Formation of Massive Mn Sediments around Sambe Hot Springs in Japan

    Okibe, Naoko, Maki, Masashi, Sasaki, Keiko, Hirajima, Tsuyoshi

    MATERIALS TRANSACTIONS   54 ( 10 ) 2027 - 2031  2013年10月  [査読有り]

     概要を見る

    There has been an increasing interest in the application of Mn(II) oxidizing microbes for Mn(II) containing waste water treatment, as well as biogenic Mn oxides for remediation of a number of toxic metals. Sambe hot spring in Shimane Prefecture, Japan is known for its Mn-rich spring water, and Mn oxide sediments are widely distributed over an area of 60 m x 80 m of this region. With an aim to find out Mn(10 oxidizing bacteria involved in this massive Mn(11) oxide deposit formation, culture enrichment was undertaken. Pseudomonas sp. strain MM1 was isolated as dominant Mn(II) oxidizing bacterium from the site. Biogenic Mn oxide formed by strain MM1 was shown to be poorly-crystalline birnessite, having the large specific surface area of 90 m(2).g(-1). Mn(II) was readily oxidized by strain MM1 during the stationary phase and initial Mn(II) concentrations of up to 1.0 mmol.dm(-3) (55 mg.dm(-3)) went well below the effluent standard of dissolved manganese (10 mg.dm(-3); set by Japanese Ministry of Environment). Strain MM1 grew heterotrophically and Mn(II) did not serve as the sole electron donor. Nano-sized (3050 nm) Mn oxide particles were produced by strain MM1, which later chained or aggregated to form larger Mn oxide minerals. Cells were observed eventually encrusted inside the Mn oxides. This study showed the important role of strain MM1 in the production of massive Mn oxide deposits at Sambe hot spring. The Mn(II) oxidizing ability of this strain is potentially applied for bioremediation of toxic metals.

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  • Characterization of lithium ion sieve derived from biogenic Mn oxide

    Qianqian Yu, Emiko Morioka, Keiko Sasaki

    MICROPOROUS AND MESOPOROUS MATERIALS   179   122 - 127  2013年09月  [査読有り]

     概要を見る

    Biogenic birnessite (BB), a stable form of manganese in the natural environment that originates from microbial oxidation, could be use as a starting material to prepare nanocrystalline lithium manganese oxide (LMO) by solid-state reaction for Li+ recovery. In this work, the effects of calcination temperature on Li+ adsorption density were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N-2 adsorption-desorption isotherms, and If ion sorption isotherms. An increase in calcination temperature causes a phase transformation that results in changes in crystal compositions. The formation of Li4Mn5O12 was observed at 350 degrees C. An increase in calcination temperature from 350 to 450 degrees C results in a decrease in the Li4Mn5O12 phase quantity, an increase in the Li2MnO3 phase quantity, and a decrease in Li+ sorption density from 4248 to 2789 mmol/kg. The sorption density of Li+ is mainly affected by the Li4Mn5O12 phase content. LMOs prepared from BB show a higher Li+ sorption density compared with acidic birnessite. Phase transformation on poorly-crystalline BB at a relatively lower calcination temperature facilitates formation of the Li4Mn5O12 phase, which is the main contributor to Li+ sorption from aqueous solution. (C) 2013 Elsevier Inc. All rights reserved.

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  • Temperature effect on the sorption of borate by a layered double hydroxide prepared using dolomite as a magnesium source

    Xinhong Qiu, Keiko Sasaki, Tsuyoshi Hirajima, Keiko Ideta, Jin Miyawaki

    CHEMICAL ENGINEERING JOURNAL   225   664 - 672  2013年06月  [査読有り]

     概要を見る

    A hydrotalcite-like compound prepared through chemical deposition using calcined dolomite as the magnesium source (D-LDH) was applied to remove borate. D-LDH calcined at different temperatures was characterized by specific surface area measurements, scanning electron microscope images, X-ray diffraction (XRD) patterns, and Fourier transform infrared (FTIR) spectra to optimize the calcination temperature and maximize the sorption capacity of borate. Greater sorption density of borate was observed at higher calcination temperature, and the sample calcined at 700 degrees C showed the maximum sorption density. In addition, the sorption density of borate by D-LDH calcined at 700 degrees C decreased with increasing initial pH. The solid residues after the sorption of borate were characterized by FTIR, B-11 NMR ((11)Boron nuclear magnetic resonance), and XRD to explore the sorption mechanism of the calcined product at 700 degrees C. (c) 2013 Elsevier B.V. All rights reserved.

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  • Effect of natural dolomite calcination temperature on sorption of borate onto calcined products

    Keiko Sasaki, Xinhong Qiu, Yukiho Hosomomi, Sayo Moriyama, Tsuyoshi Hirajima

    MICROPOROUS AND MESOPOROUS MATERIALS   171   1 - 8  2013年05月  [査読有り]

     概要を見る

    Natural dolomite was calcined at 700-900 degrees C under air and an Ar gas flow atmosphere to characterize its sorbency potential for borate. A sequential decarbonation occurred with increase in calcination temperature, that is, transformation of CaMg(CO3)(2) to MgO and CaCO3 up to 700 degrees C and CaCO3 to CaO from 700 to 900 degrees C. The surface molar ratio of Ca/Mg decreased from 1.6 to 0.6 by calcination at more than 700 degrees C, owing to the crystal growth of MgO toward the surfaces. MgO crystal growth is responsible for hydration leading to borate co-precipitation. The sorption density of borate was greater with the calcined products at 700 degrees C than 800-900 degrees C and under an Ar gas flow system rather than for static air at the same temperatures. The surface reactivity of the calcined dolomite with borate in the aqueous phase was affected by CO2 emitted in the decarbonation at higher temperatures. (C) 2012 Elsevier Inc. All rights reserved.

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  • Geochemical and Microbiological Analysis of Sambe Hot Springs, Shimane Prefecture, Japan

    Keiko Sasaki, Yoshitaka Uejima, Atsushi Sakamoto, Qianqian Yu, Junichiro Ishibashi, Naoko Okibe, Tsuyoshi Hirajima

    Resource Geology   63 ( 2 ) 155 - 165  2013年04月  [査読有り]

     概要を見る

    Microbiological contribution to the formation of the manganese deposits in Sambe hot springs, Shimane, was investigated in combination with water chemistry, characterization of sediments and microbial community structure. Analysis of bacterial and fungal community structure based on DNA extracted from a Mn-oxidizing enrichment culture indicated close matches with Pseudomonas putida, Phoma sp. and Plectosphaerella cucumerina, all Mn-oxidizing microorganisms. These sediments were poorly crystalline and formed at neutral pH values, which is characteristic of biogenic precipitates. The EPMA results demonstrated a positive correlation between Mn and Ba contents in well-crystalline Mn oxide grains. Substantial Ba contents were observed inside Mn oxide grains. These findings indicated that Ba contents in sediments are influenced by not only aqueous Ba2+ concentrations but also crystallinity of biogenic birnessite. Barium would be incorporated in birnessite during biomineralization. © 2013 The Society of Resource Geology.

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    6
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  • Simultaneous oxidation and immobilization of arsenite from refinery waste water by thermoacidophilic iron-oxidizing archaeon, Acidianus brierleyi

    N. Okibe, M. Koga, K. Sasaki, T. Hirajima, S. Heguri, S. Asano

    Minerals Engineering   48   126 - 134  2013年  [査読有り]

     概要を見る

    The use of a thermophilic acidophilic iron-oxidizing archaeon, Acidianus brierleyi, was investigated for oxidation and immobilization of As(III) from acidic refinery waste water. Some As(III) oxidation was measured in all Ac. brierleyi cultures independently of the presence or concentration of Fe(II) in bulk solution; the exception was at initial Fe(II) concentration ([Fe(II)] ini) of 1000 mg l-1 where As(III) oxidation became markedly facilitated and consequently approximately 70% of As was immobilized as amorphous ferric arsenate. Providing 1000 mg l-1 Fe(III) instead of Fe(II) did not show the same effect, implying the importance of Fe(III) be microbially-produced and complexed in the archaeal EPS (extracellular polymeric substances) region for effective As(III) oxidation. The reaction towards secondary mineral formation shifted from ferric arsenate to jarosite at [Fe(II)]ini of >1000 mg l-1. Furthermore addition of jarosite seed crystals retarded the As(III) oxidation rate at [Fe(II)] ini of 1000 mg l-1. The observations indicate that by setting the appropriate bulk Fe(II)/As(III) ratio in Ac. brierleyi culture to achieve a certain concentration of Fe(III) within the EPS region, but at the same time to avoid jarosite formation, it is possible to maximize the As(III) oxidation rate and thus As immobilization efficiency. This study describes for the first time microbially-mediated simultaneous oxidation and immobilization of As(III) as ferric arsenate, using a thermoacidophilic iron-oxidizing archaeon, Ac. brierleyi. © 2012 Elsevier Ltd. All rights reserved.

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  • Sorption of fluoride on partially calcined dolomite

    Keiko Sasaki, Mari Yoshida, Bashir Ahmmad, Naoyuki Fukumoto, Tsuyoshi Hirajima

    Colloids and Surfaces A: Physicochemical and Engineering Aspects   435   56 - 62  2013年  [査読有り]

     概要を見る

    Natural dolomite was calcined at different temperatures in the range 873-1373K and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and N2 adsorption/desorption isotherm. The calcination temperature had considerable effect on the surface chemical composition, crystallinity, and basicity of CO2 gas sorption of each component in the calcined products. The sorption isotherm of both in low and high concentrations of fluoride (F-) was investigated for selected calcination products. The sample calcined at 973K was found to show the highest sorption density for F- at equilibrium concentrations lower than 0.5mM, which was equivalent to the maximum concentration limit of F-. In this range, the principle of F- removal is mainly based on destructive hydration of MgO. At equilibrium concentrations of F- higher than 0.5mM, the sorption process was controlled by precipitation of CaF2 and co-precipitation with Ca(OH)2 due to excess liberation of Ca2 ions from CaO. In this concentration region the products of calcination at higher temperatures are profitable for the immobilization of F-. Additionally, the effect of CO2 gas derived from carbonates on the reactivity of MgO to remove F- during calcination of natural dolomite was also discussed. © 2012 Elsevier B.V.

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  • Sorption Kinetic of Arsenate as Water Contaminant on Zero Valent Iron

    Osama Eljamal, Keiko Sasaki, Tsuyoshi Hirajima

    Journal of Water Resource and Protection   05 ( 06 ) 563 - 567  2013年

    DOI DOI2

  • Application of plasma treated activated carbon to enhancement of phenol removal by ozonation in three-phase fluidized bed reactor

    Pilasinee Limsuwan, Satoshi Kumagai, Moriyasu Nonaka, Keiko Sasaki, Wiwut Tanthapanichakoon, Tsuyoshi Hirajima

    Advanced Materials Research   701   305 - 309  2013年  [査読有り]

     概要を見る

    Plasma treatment of activated carbon (AC) was found to be an efficient method to enhance phenol removal by ozonation in a three-phase fluidized-bed reactor. The plasma treatment extended porous structure, changed surface morphologies, and produced oxygen functional groups on the surface of AC. Plasma-treated activated carbon together with O3 gave the best removal result, in which phenol was completely decomposed within 10 min (with pseudo first-order rate constant k = 0.286 min-1), while untreated AC without O3 showed the worst result (k = 0.024 min-1). Consequently, AC modified by plasma was shown to be a good material for removal of organic pollutants and yield superb performance in an integrated process with ozone in a fluidized-bed reactor. © (2013) Trans Tech Publications, Switzerland.

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  • Gravity separation and its effect on CO2 gasification

    Moriyasu Nonaka, Tsuyoshi Hirajima, Keiko Sasaki

    Fuel   103   37 - 41  2013年01月  [査読有り]

     概要を見る

    The CO2-blown integrated coal gasification combined cycle (IGCC) is a promising electric power generation technology that will reduce CO 2 emission, due to its high efficiency. Recent studies have found that base metals improve the coal char gasification in cases when they can interact with the char matrix at an atomic level. In this paper, we clarified the effect of heavy medium separation, which is one of the most popular coal cleaning technologies, on the CO2 char gasification. Before sink and float test and thermogravimetric analysis, Datong Coal from China was ground to below 20 mesh, which is a size usually used for a coal cleaning process. The float and sink test revealed that the highest separation efficiency would be obtained at a specific gravity of 1.45. The ash content would be reduced dramatically from 10.2% to ca. 4% and about 85% of combustibles would be recovered. The chars derived from different specific gravity fractions showed different gasification reactivity
    the char from heavier fraction has gasification reactivity higher than the lighter fraction-derived char. This tendency agrees with the ash content
    the heavier fraction has a higher ash content. Removal of ash from well-ordered holes in Fusinite and Semi-fusinite in Inertinite might increase the gasification reactivity. © 2012 Elsevier Ltd. All rights reserved.

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    6
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  • Characteristic Sorption of H3BO3/B(OH)(4)(-) on Magnesium Oxide

    Keiko Sasaki, Xinhong Qiu, Sayo Moriyama, Chiharu Tokoro, Keiko Ideta, Jin Miyawaki

    MATERIALS TRANSACTIONS   54 ( 9 ) 1809 - 1817  2013年  [査読有り]

     概要を見る

    The reaction mechanism of H3BO3/B(OH)(4)(-) with MgO in aqueous phase was investigated using sorption isotherm, XRD, B-11-NMR and FTIR. Release of Mg2+ was observed soon after contact of MgO with H3BO3 and maximum released Mg2+ was proportional to the initial boron concentration, suggesting ligand-promoted dissolution of MgO by H3BO3. The molecular form of H3BO3 was more reactive with MgO in releasing Mg2+ ions than B(OH)(4)(-). B-11-NMR results indicated that trigonal B (B-[3]) was predominant over tetrahedral B (B-[4]) in solid residues after sorption of H3BO3. The molar ratio of B-[4]/B-[3] increased with H3BO3 sorption density. XRD patterns for the solid residues were assigned to Mg(OH)(2) and peaks broadened with increasing H3BO3 sorption density, except for (hk0) planes due to c-axis lattice strain induced by incorporation of H3BO3 between layers. These results indicated that H3BO3 interfered in the c-axis stacking of in Mg(OH)(2). Molecular H3BO3 acted as a trigger when reacting with the MgO surface, releasing Mg2+ to produce an unstable complex leading to the precipitation formation of Mg(OH)(2), which is a sink for the immobilization of H3BO3/B(OH)(4)(-).

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    35
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  • Synthesis of biogenic Mn oxide and its application as lithium ion sieve

    Qianqian Yu, Emiko Morioka, Tsuyoshi Hirajima, Keiko Sasaki

    INTEGRATION OF SCIENTIFIC AND INDUSTRIAL KNOWLEDGE ON BIOHYDROMETALLURGY   825   439 - 442  2013年  [査読有り]

     概要を見る

    Geomimetics, taking lessons from nature's biogenic mineralization mechanisms, can provide powerful tools for advancing biohydrometallurgical processing. Microbial transformations are largely responsible for the Mn oxides found in nature. In this research biogenic birnessite was produced by a manganese-oxidizing fungus, Paraconiothyrium sp. WL-2, at pH 6.5 under room temperature, and characterized by XRD and TG-DTA. Abiotic (chemically synthesized) acidic birnessite was also prepared hydrometallurgically and subjected to a similar battery of characterization techniques. Following thermal treatment the sorption characteristics of these two materials were compared. The biogenic precursor showed several advantages to produce more effective Li-ion sieve than the chemically synthesized precursor. First, a shorter calcination period was required to produce Li4Mn5O12 without other phases; second, a greater content and higher crystallinity of H4Mn5O12 were obtained from the biogenic precursor. These advantages might be caused by poorer crystallinity and around 20 wt% organic matter in biogenic birnessite. While sorption density of Li+ in mmol/g was basically dependent on contents of H4Mn5O12 phase, the unique morphologies and sorption density were maintained with biogenic precursor even after repetition of sorption/desorption of Li+.

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    2
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  • Production of 5-hydroxymethyl Furfural from Sugarcane BagasseUnder Hot Compressed Water

    Iryani Dewi Agustina, Kumagai Satoshi, Nonaka Moriyasu, Sasaki Keiko, Hirajima Tsuyoshi

    INTERNATIONAL CONFERENCE ON EARTH SCIENCE AND TECHNOLOGY PROCEEDINGS   6   441 - 447  2013年  [査読有り]

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  • Spectroscopic analysis of the bioleaching of chalcopyrite by Acidithiobacillus caldus

    Keiko Sasaki, Koichiro Takatsugi, Olli H. Tuovinen

    HYDROMETALLURGY   127   116 - 120  2012年10月  [査読有り]

     概要を見る

    The formation and consumption of elemental S were investigated in the bioleaching of chalcopyrite within and without a CE dialysis membrane in Acidithiobacillus caldus cultures. The bacteria were supplemented with tetrathionate outside the membrane. XPS analysis showed that monosulfide species and elemental S were formed on CuFeS2 surface regardless of the enclosure in the dialysis membrane. They diminished over time in the inoculated systems. In the membrane enclosure, colloidal S partially dissolves and can pass the dialysis membrane for bacterial oxidation to sulfuric acid. Anaerobic pre-oxidation of CuFeS2 by Fe3+ produced S-rich deposition on mineral surface. The solubilization of Cu from membrane-enclosed pre-oxidized chalcopyrite in the A. caldus culture was much slower as compared to direct contact with bacteria. The difference is attributed to slow diffusion through the dialysis membrane as well as clogging caused by polymerized S on the inside of the membrane. (C) 2012 Elsevier B.V. All rights reserved.

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    8
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  • Chemical regeneration of magnesium oxide used as a sorbent for fluoride

    Keiko Sasaki, Naoyuki Fukumoto, Sayo Moriyama, Qianqian Yu, Tsuyoshi Hirajima

    SEPARATION AND PURIFICATION TECHNOLOGY   98   24 - 30  2012年09月  [査読有り]

     概要を見る

    Use of MgO for repeated calcination with regard to its sorption density for F- and chemical stability was examined. Magnesium oxide was produced by the calcination of MgCO3 at 1273 K for 1 h. The sorption of 9.82 mM F- on the calcined product and the calcinations of solid residues were carried out five times to evaluate trends in sorption density for F- and the stability of the chemically regenerated sorbents. The order of sorption density of F- (Q/mol g(-1)) apparently seems to depend on the specific surface area. However. Q' values after normalization of the sorption density for the specific surface area (Q'/mmol m(-2)) were found to be correlated with the solid basicities of the calcined products which were derived from CO2-TPD curves for the calcined products. The number of weak base sites, calculated from the peak intensity at 373 K in CO2-TPD, was considered to be responsible for the removal of F- through hydration. Large quantities of NaMgF3 and elemental Mg were evaporated by the calcination at 1273 K of the solid residues formed after sorption of F-. (c) 2012 Elsevier B.V. All rights reserved.

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  • Ion Exchange Capacity of Sr2+ onto Calcined Biological Hydroxyapatite and Implications for Use in Permeable Reactive Barriers

    Keiko Sasaki, Shoichi Tsuruyama, Sayo Moriyama, Stephanie Handley-Sidhu, Joanna C. Renshaw, Lynne E. Macaskie

    MATERIALS TRANSACTIONS   53 ( 7 ) 1267 - 1272  2012年07月  [査読有り]

     概要を見る

    With the recent Fukushima incident, there is an urgent need to find cost effective and workable permeable reactive barrier (PRBs) for the remediation/retardation of problematic radionuclides. Catfish bones were calcined at various temperatures (400-1100 degrees C) to remove the organic matter (87.1 mg-g(-1)) and to change the structural properties of the hydroxyapatite (HAP). Increasing temperatures increased the HAP crystallinity as indicated by a decrease in lattice strain (0.0098 to 0.00135) and an increase in crystallite sizes (5.0 x 10(-8) to 7.7 x 10(-8) m). There was also an observed decrease in specific surface areas (98.9 to 0.99 m(2)-g(-1)) and increase in particle sizes (50 to 1000 nm). The sorption densities of Sr2+ decreased with increasing calcination temperatures, from 0.34 to 0.05 mmol.g(-1). However, once normalized for surface area, the sorption densities increased from 1.8 to 5.9 mmol.m(-2). Overall, this research has important implications for the design of hydroxyapatite PRBs with higher calcination temperatures producing a more reactive material with larger particle sizes for increased permeability. Lower calcination temperatures produced amorphous HAP material, which released more aqueous PO43- and resulted in the precipitation of strontium phosphates, ultimately reducing the permeability of PRBs. [doi:10.2320/matertrans.M-M2012813]

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  • Structural factors of biogenic birnessite produced by fungus Paraconiothyrium sp WL-2 strain affecting sorption of Co2+

    Qianqian Yu, Keiko Sasaki, Kazuya Tanaka, Toshihiko Ohnuki, Tsuyoshi Hirajima

    CHEMICAL GEOLOGY   310   106 - 113  2012年06月  [査読有り]

     概要を見る

    The surface reactivity of biogenic birnessite is attributed to its structure. However, structural control of heavy metal adsorption on biogenic birnessite is not well understood. Here a poorly-crystalline birnessite was produced by the fungus Paraconiothyrium sp. WL-2 strain under ambient pH and temperature conditions. The structure was characterized by X-ray absorption spectroscopy and X-ray diffraction. Sorption behaviors of Co2+ were compared with Zn2+. The primary product of the Mn bio-oxidation is hexagonal birnessite with a turbostratic structure. XAFS analysis demonstrated that the biogenic birnessite consists of octahedral sheets with Mn(IV) as the central metal and some vacant sites. Mn(III) atoms are coordinated to some of the vacant sites in the interlayer. The adsorption of Co2+ by the biogenic birnessite is higher than Zn2+. The excess adsorption of Co2+ than Zn2+ is nearly the same as the excess release of Mn from the biogenic birnessite. These results strongly suggested that the interlayer Mn(III) can oxidize the adsorbed Co2+ to Co3+, resulting in excess adsorption of Co2+ compared to Zn2+ by biogenic birnessite. (C) 2012 Elsevier B.V. All rights reserved.

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  • Effect of microorganisms on flocculation of quartz

    Tsuyoshi Hirajima, Yuki Aiba, Mohsen Farahat, Naoko Okibe, Keiko Sasaki, Takehiko Tsuruta, Katsumi Doi

    International Journal of Mineral Processing   102-103   107 - 111  2012年01月  [査読有り]

     概要を見る

    Application of microorganisms as surface modifiers in flocculation has generated a great deal of interest in recent times. The surface properties such as zeta-potential and hydrophobicity of minerals and microorganisms play a major role in determining the adsorption of microorganisms onto the minerals and hence the efficiency of flocculation. The utility of microorganisms, including Escherichia coli (wild-type and genetically modified strain Sip), Arthrobacter nicotianae, Bacillus licheniformis, and Pseudomonas maltophilia, has been evaluated by measuring their zeta-potentials and carrying out adsorption and flocculation experiments. Of the tested microorganisms, adsorption of E. coli strain Sip significantly modified the quartz surface. The zeta-potential of the quartz became highly positive at acidic pH, and its IEP (isoelectric point) was shifted from pH < 2 to pH 4.3. Moreover, the settling velocity of the bio-treated quartz reached its maximum value at this pH. The number of cells adsorbed onto quartz was low at pH above the IEP due to the identical surface charges of the mineral and bacterial cells. This led to a repulsive force between the mineral particles and bacterial cells, which hindered the adsorption process. For all of the studied strains, the settling velocity of bio-treated quartz was high at their respective IEPs. An interaction model of microorganisms is proposed to explain the flocculation behavior of bio-treated quartz. Potential energies were calculated using the DLVO theory, and the results were found to be in good agreement with the flocculation tests. The settling velocity of the bio-treated quartz was maximized at pH close to the IEP of microbial cells. Interaction between cells is identified as the most likely cause of flocculation of bio-treated quartz. © 2011 Elsevier B.V. All rights reserved.

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  • Effects of sodium thiosulphate on chalcopyrite and tennantite: An insight for alternative separation technique

    Himawan T. B. M. Petrus, Tsuyoshi Hirajima, Keiko Sasaki, Hideyuki Okamoto

    INTERNATIONAL JOURNAL OF MINERAL PROCESSING   102   116 - 123  2012年01月  [査読有り]

     概要を見る

    In this study, the effects of sodium thiosulphate on chalcopyrite and tennantite at various pH values were investigated. Contact angle, flotation (Hallimond tube), zeta potential and X-ray photoelectron spectroscopy were used to observe these effects and to investigate the mechanisms involved. The addition of sodium thiosulphate depressed both chalcopyrite and tennantite at all pH values. Further addition of diethyl dithiophosphate significantly increased the notability of chalcopyrite at all pH values as well as tennanite in acidic conditions, but not tennantite in alkaline conditions. In light of the zeta potential measurements and due to the stability of thiosulphate over the pH range, the coverage of sulphate resulting from the oxidation of thiosulphate was responsible for the depression of both chalcopyrite and tennantite in acidic conditions. Adsorption of diethyl dithiophosphate species on the mineral surface resulted in notability of tennantite which was almost as high as that of chalcopyrite. In alkaline conditions, coverage of the copper thiosulphate complex was responsible for the depression. The copper thiosulphate complex inhibited adsorption of diethyl dithiophosphate species on the mineral surface. Higher coverage of the copper thiosulphate complex on tennantite caused an insignificant increase in its notability in comparison to that of chalcopyrite which allowed the separation of tennantite from chalcopyrite. The XPS spectra supported the proposed mechanism of thiosulphate depression on these minerals. (C) 2011 Elsevier B.V. All rights reserved.

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    22
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  • Characterization of Passivation Layers in Bioleaching of Sulfides

    Keiko Sasaki

    BUNSEKI KAGAKU   60 ( 12 ) 911 - 919  2011年12月  [査読有り]

     概要を見る

    During the process for the bioleaching of sulfides, the surface of the target mineral is sometimes covered with intermediates, and the final products that interfere with the extraction of the target metal. Understanding the characterization and formation order of the secondary minerals responsible for passivation is a key to resolving the passivation mechanism. The present article reviews identification of secondary minerals and intermediates in a process of bioleaching of several sulfides by X-ray photoelectron spectroscopy, Raman spectroscopy', identification of the jarosite group minerals using Raman spectroscopy, and expectation of the formation order of the secondary minerals by SEM-EDX and TEM. The TEM observation in a nano-domain provides useful information about amorphous the secondary minerals. A passivation model was proposed to keep maximizing Cu recovery and minimizing As solubilization for the bioleaching of arsenic-bearing copper sulfides using super-thermophilic archaea, which are expected to be new target minerals in the near future.

    DOI

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  • Numerical simulation for reactive solute transport of arsenic in permeable reactive barrier column including zero-valent iron

    Osama Eljamal, Keiko Sasaki, Tsuyoshi Hirajima

    APPLIED MATHEMATICAL MODELLING   35 ( 10 ) 5198 - 5207  2011年10月  [査読有り]

     概要を見る

    Numerical modeling was developed in one dimensional solute transport including chemical reaction to simulate the permeable reactive barrier column results, in which arsenite (As(III)) was removed using zero-valent iron (ZVI). Removal principles of As(Ill) includes oxidation of As(III) to As(V), sorption of As(III) and sorption of As(V) at least. Each kinetic parameter was drawn in preliminary batch tests to integrate the simulation.The column simulation results show that As(V) adsorption rate was faster than the As(III) adsorption rate and that they are affected by the available mass of Fe(III) in the system. The model can be used to design and predict the long term performance of ZVI permeable reactive barriers (PRBs). (C) 2011 Elsevier Inc. All rights reserved.

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  • Study of Diethyl Dithiophosphate Adsorption on Chalcopyrite and Tennantite at Varied pHs

    H. T. B. M. Petrus, T. Hirajima, K. Sasaki, H. Okamoto

    JOURNAL OF MINING SCIENCE   47 ( 5 ) 695 - 702  2011年09月  [査読有り]

     概要を見る

    The kinetics of diethyl dithiophosphate adsorption on chalcopyrite and tennantite has been studied by UV-visible spectroscopy at pH values of 4, 6, and 9. The concentration of diethyl dithiophosphate in the solution has been monitored as a function of time and pH for both minerals. It was found that the adsorption tendency of diethyl dithiophosphate on both minerals decreased with the increasing pH treatments. This is due to the existence of metal hydroxide species onto the mineral surface in more alkaline condition inhibiting the adsorption of diethyl dithiophosphate species. In comparison to that of chalcopyrite, tennantite possessed slightly higher adsorption of diethyl dithiophosphate in acid condition, while vice versa correlation observed at other pH treatments at where the coverage of metal hydroxide species obtained higher than that of chalcopyrite showing that the rate oxidation of tennantite is higher. An adsorption mechanism has been proposed and tested against the experimental kinetic data. Both the kinetic data and flotation studies are consistent with the proposed mechanism.

  • Mechanism of the enhancement of bioleaching of copper from enargite by thermophilic iron-oxidizing archaea with the concomitant precipitation of arsenic

    Koichiro Takatsugi, Keiko Sasaki, Tsuyoshi Hirajima

    HYDROMETALLURGY   109 ( 1-2 ) 90 - 96  2011年09月  [査読有り]

     概要を見る

    Bioleaching of enargite by the thermophilic iron-oxidizing archaea, Acidianus brierleyi, at 70 degrees C for 27 days yielded a 90.9% recovery of Cu and 5.9% recovery of As. The preferential dissolution of Cu compared to As was mainly achieved by the formation of crystalline scorodite (FeAsO(4)center dot 2H(2)O). Although the chemical valence of As in enargite was confirmed to be As(III), most of the dissolved As was in the compound H(3)As(V)O(4). This indicates that the H(3)As(III)O(3) released from the enargite was immediately oxidized to H(2)As(V)O(4)(-) in solution via a catalytic reaction on the surface of the enargite. During the bioleaching process, dissolved Fe(3+) was consumed through the formation of precipitates, such as scorodite and jarosite ((M(+))Fe(3)(SO(4))(2)(OH)(6)), as well as the oxidation of enargite. Even after the formation of scorodite had stopped due to the consumption of Fe(3+), As was further passivated in the absence of Fe(3+). The co-sorption of Cu(2+) and H(2)As(V)O(4)(-) on jarosite led to the formation of copper arsenate by a seed-forming effect. Subsequent secondary mineral precipitation resulted in the formation of multi-precipitation layers consisting of scorodite, potassium jarosite, elemental sulfur and copper arsenate, after most of the Cu had been recovered from the enargite by microbially induced leaching. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.

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  • Effects of initial Fe2+ concentration and pulp density on the bioleaching of Cu from enargite by Acidianus brierleyi

    Keiko Sasaki, Koichiro Takatsugi, Tsuyoshi Hirajima

    HYDROMETALLURGY   109 ( 1-2 ) 153 - 160  2011年09月  [査読有り]

     概要を見る

    To maximize Cu recovery and minimize As release during the bioleaching of enargite (Cu3AsS4) by Acidianus brierleyi at 70 degrees C, the initial Fe2+ ion concentration and pulp density were investigated in batch tests. A maximum Cu recovery of 91.0 +/- 0.5% was obtained with an initial Fe2+ ion concentration of 1.8-2.7 g/L and a pulp density of 1.0%. As the immobilization of As depended on the formation of scorodite (FeAsO4 center dot 2H(2)O) and cupric arsenate, a more rapid and stable As immobilization was achieved with an initial Fe2+ ion concentration of 2.7 g/L Thus the initial Fe2+ concentration of 2.7 g/L and 1.0% pulp density provided for a combination of As precipitation and &gt;90% Cu recovery. When the initial Fe2+ concentration was increased, K-jarosite (KFe3(SO4)(2)(OH)(6)) precipitated, leading to passivation of the enargite surface. When the initial Fe2+ concentration was lowered, the Cu recovery was incomplete due to insufficient oxidation. Elevating the pulp density to 2.0% showed that the increase in Eh significantly lagged behind the exponential phase in the planktonic cell growth curve. Pulp density also clearly affected the makeup of secondary minerals in solid residues after the bioleaching of enargite. There is a tendency for dissolved Fe3+ ions to readily precipitate as potassium jarosite at relatively smaller pulp densities and as scorodite at relatively larger pulp densities. (C) 2011 Elsevier B.V. All rights reserved.

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  • Effect of pH and diethyl dithiophosphate (DTP) treatment on chalcopyrite and tennantite surfaces observed using atomic force microscopy (AFM)

    Himawan T. B. M. Petrus, Tsuyoshi Hirajima, Keiko Sasaki, Hideyuki Okamoto

    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS   389 ( 1-3 ) 266 - 273  2011年09月  [査読有り]

     概要を見る

    Atomic force microscopy (AFM) has been used to observe the morphology and surface characteristics of chalcopyrite and tennantite treated at pH 4 and 9. Mineral treated with DTP at pH 9 was also observed. It was found that new surface "islands" were formed on the minerals after these treatments. The occurrence of these islands as a product of reaction was amplified with increasing treatment time. Adhesion force measurements revealed that the formation of islands under acidic conditions (pH 4) lowered the adhesion force value compared to that under alkaline conditions (pH 9), thus rendering the surfaces of the minerals more hydrophobic. A similar tendency was observed in the adhesion force value of minerals surface-treated with DTP at pH 9. This phenomenon arose as a result of a propensity for the formation of elemental sulfur or metal-deficient sulfur-rich species at pH 4 and DTP species at pH 9. The more hydrophilic surfaces of both minerals indicated by higher values of the adhesion force after treatment at pH 9 may be attributed to the occurrence of metal hydroxide moieties. From the morphology images and adhesion force, it is apparent that the coverage of islands on the surface of a mineral determines its hydrophobicity or hydrophilicity. Moreover, it also shows the relative reactivities of the minerals, with tennantite being more reactive than chalcopyrite. Furthermore, the microscopic observation by AFM was consistent with the macroscopic observations of contact angle and flotability studies. (C) 2011 Published by Elsevier B.V.

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  • Uptake of Sr 2+ and Co 2+ into biogenic hydroxyapatite: Implications for biomineral ion exchange synthesis

    S. Handley-Sidhu, J. C. Renshaw, S. Moriyama, B. Stolpe, C. Mennan, S. Bagheriasl, P. Yong, A. Stamboulis, M. Paterson-Beedle, K. Sasaki, R. A D Pattrick, J. R. Lead, L. E. MacAskie

    Environmental Science and Technology   45 ( 16 ) 6985 - 6990  2011年08月  [査読有り]

     概要を見る

    Biomineral hydroxyapatite (Bio-HAp) produced by Serratia sp. has the potential to be a suitable material for the remediation of metal contaminated waters and as a radionuclide waste storage material. Varying the Bio-HAp manufacturing method was found to influence hydroxyapatite (HAp) properties and consequently the uptake of Sr 2+ and Co 2+. All the Bio-HAp tested in this study were more efficient than the commercially available hydroxyapatite (Com-HAp) for Sr 2+ and Co 2+ uptake. For Bio-HAp the uptake for Sr 2+ and Co 2+ ranged from 24 to 39 and 29 to 78 mmol per 100 g, respectively. Whereas, the uptake of Sr 2+ and Co 2+ by Com-HAp ranged from 3 to 11 and 4 to 18 mmol per 100 g, respectively. Properties that increased metal uptake were smaller crystallite size (&lt
    40 nm) and higher surface area (&gt
    70 m 2 g -1). Organic content which influences the structure (e.g., crystallite arrangement, size and surface area) and composition of Bio-HAp was also found to be important in Sr 2+ and Co 2+ uptake. Overall, Bio-HAp shows promise for the remediation of aqueous metal waste especially since Bio-HAp can be synthesized for optimal metal uptake properties. © 2011 American Chemical Society.

    DOI PubMed

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  • Upgrading of low rank coal and woody biomass mixture by hydrothermal treatment

    Moriyasu Nonaka, Tsuyoshi Hirajima, Keiko Sasaki

    FUEL   90 ( 8 ) 2578 - 2584  2011年08月  [査読有り]

     概要を見る

    Attempts to produce high-grade fuel from biomass and low rank coal are important from the viewpoint of renewable energy and the utilization of unused resources. In this paper, the authors reported on the hydrothermal treatment of biomass and low rank coal at 300 degrees C using a bench scale continuous apparatus and a batch autoclave. The results show that coalification takes place during the hydrothermal treatment of both the low rank coal and biomass, and the upgraded solid products show similar chemical compositions, gross calorific value and effective calorific value, independent of the mixing ratio. The solid product also becomes hydrophobic and unable to re-adsorb the lost moisture. The characteristics of the solid produced by the bench scale continuous apparatus can be predicted by the results of the batch process. Thermogravimetric analysis shows that the solid product has a wide-range of molecular weight but the thermally stable heavy molecules are found more in the treated coal as opposite to the thermally unstable light molecules, more of which are found in the treated biomass. This may correlate with that the solid product of higher biomass mixing ratio has a higher volatile matter content. Polymerization is synergistically promoted during mixed hydrothermal treatment of low rank coal and biomass. (C) 2011 Elsevier Ltd. All rights reserved.

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  • Sorption characteristics of fluoride on to magnesium oxide-rich phases calcined at different temperatures

    Keiko Sasaki, Naoyuki Fukumoto, Sayo Moriyama, Tsuyoshi Hirajima

    JOURNAL OF HAZARDOUS MATERIALS   191 ( 1-3 ) 240 - 248  2011年07月  [査読有り]

     概要を見る

    The effect of calcination temperature during production of magnesium oxide-rich phases from MgCO(3) on the sorption of F(-) ions in the aqueous phase has been investigated. Magnesium oxide-rich phases were formed by calcination at over 873 K for 1 h. Higher calcination temperatures produced more crystalline MgO with smaller specific surface area and provided larger values of the total basicity per unit surface area. The higher calcination temperatures lead to slower F(-) removal rate, and lower equilibrium F(-) concentrations, when the equilibrium F(-) concentrations are less than 1 mmol dm(-3). Larger total basicity per unit surface area made the reactivity with F(-) ions in aqueous phase more feasible, resulting in a greater degree of F(-) sorption. For equilibrium F(-) concentrations more than 1 mmol dm(-3), lower calcination temperatures favored the co-precipitation of F(-) with Mg(OH)(2), probably leading to the formation of Mg(OH)(2-x)F(x), and the achievement of larger sorption density. This is the first paper which describes the relationship between the solid base characteristics obtained by CO(2)-TPD for MgO with different calcination temperatures as a function of the reactivity of F(-) sorption in the aqueous phase. (C) 2011 Elsevier B.V. All rights reserved.

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    45
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  • Kinetic Model of Arsenic Sorption onto Zero-Valent Iron (ZVI)

    Osama Eljamal, Keiko Sasaki, Shoichi Tsuruyama, Tsuyoshi Hirajima

    WATER QUALITY EXPOSURE AND HEALTH   2 ( 3-4 ) 125 - 132  2011年02月  [査読有り]

     概要を見る

    This study investigated the mechanisms involved in removing arsenic from water using zero-valent iron (ZVI) as sorbent. Relatively limited information is available on the kinetics aspects of sorption of arsenic compounds onto ZVI. In order to gain an understanding of the sorption kinetics, a detailed study was conducted in a controlled batch test and developed sorption kinetic model.The effects of different arsenic concentrations on the kinetics sorption rates of arsenic(V) and arsenic(III) were investigated. Arsenic(V) was removed by two mechanisms-surface adsorption and co-precipitation with Fe(III) on ZVI, while arsenic(III) was removed by adsorption on ZVI and oxidized to arsenic(V). Reaction rate constants were calculated for arsenic(V) and arsenic(III) at different concentrations by a second-order kinetic model.The results indicate that ZVI could be employed as sorbent materials to enhance the adsorption and co-precipitation processes to improve the removal rate of arsenic from water. The results also showed that the arsenic(III) oxidized to arsenic(V), while the analyses indicated that there was no measurable reduction of arsenic(V) to arsenic(III).

    DOI

  • Erratum: 微生物による硫化鉱物の浸出反応における不動態化層の特性化[分析化学60巻12号,911~919頁]

    笹木 圭子

    分析化学   61 ( 1 ) 69 - 69  2011年

     概要を見る

    [Additions]「分析化学」第60巻第12号にて,印刷会社のミスにより下記の誤りがございましたので,お詫びするとともに訂正いたします(PDF参照).

    DOI CiNii

  • Effect of saw dust on borate removal from groundwater in bench-scale simulation of permeable reactive barriers including magnesium oxide

    K. Sasaki, H. Takamori, S. Moriyama, H. Yoshizaka, T. Hirajima

    JOURNAL OF HAZARDOUS MATERIALS   185 ( 2-3 ) 1440 - 1447  2011年01月  [査読有り]

     概要を見る

    Effective immobilization of boron in groundwater is a major challenge. Permeable reactive barrier (PRB) column tests for removal of borate have been investigated using MgO agglomerates as the primary reactive material over 40 weeks. Additionally, saw dust was also blended with MgO agglomerates to facilitate for borate removal in this system. Boron accumulation was more than 1.6 times greater in the presence of saw dust, although MgO alone performed well. Increased boron accumulation in the presence of saw dust was primarily due to higher porosity of the PRB column, decreasing the impact of secondary Mg(OH)(2) passivating layers and leaving more reactive sites on MgO agglomerates. In addition, Mg(2+) ions released from MgO agglomerates are complexed with carboxylic acids leached from saw dusts. This sequestration prevents the formation of bulky Mg(OH)(2) which is an ineffective sorbent for borate and covers the surfaces and passivating reactive sites on the MgO agglomerates. The morphologies of Mg(OH)(2) precipitated in the PRB column were also significantly affected by the presence of saw dust, with crystallization of needle-like particles of Mg(OH)(2) was prevented by Mg(2+) ions-organic ligand complexation. (C) 2010 Elsevier B.V. All rights reserved.

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  • Alkaline hydrothermal de-ashing and desulfurization of low quality coal and its application to hydrogen-rich gas generation

    Anggoro Tri Mursito, Tsuyoshi Hirajima, Keiko Sasaki

    ENERGY CONVERSION AND MANAGEMENT   52 ( 1 ) 762 - 769  2011年01月  [査読有り]

     概要を見る

    This paper describes experimental research and a fundamental study of alkaline hydrothermal treatment of high-sulfur, high-ash coal from Banten, Java-Indonesia. Experiments were carried out on a laboratory-scale 0.5 L batch reactor. The alkaline hydrothermal treatment gave upgraded clean coal with low sulfur content (about 0.3 wt.%) and low ash content (about 2.1 wt.%). A zero carbon dioxide and pure hydrogen gas were produced at 330 degrees C by introducing an alkali (sodium hydroxide, NaOH) to the hydrothermal treatment of raw coal. X-ray diffraction (XRD) and X-ray fluorescence (XRF) techniques were used to test for the removal or reduction of major, inorganic elements in the coal, and changes in carbon-functional groups and their properties were determined by Fourier transform infrared spectroscopy (FTIR) and Carbon-13 of nuclear magnetic resonance ((13)C NMR) tests on the product of the hydrothermal upgrading and demineralization process. (C) 2010 Elsevier Ltd. All rights reserved.

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    36
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  • Performance of dry-separation processes in the recovery of cenospheres from fly ash and their implementation in a recovery unit

    H. T. B. M. Petrus, Tsuyoshi Hirajima, Yuji Oosako, Moriyasu Nonaka, Keiko Sasaki, Takashi Ando

    INTERNATIONAL JOURNAL OF MINERAL PROCESSING   98 ( 1-2 ) 15 - 23  2011年01月  [査読有り]

     概要を見る

    Cenospheres recovery is one of the coal fly ash beneficiations, providing economic as well as environmental benefits. Current techniques, such as lagoon or other wet-separation processes, consume large amounts of water and add to water pollution due to leaching of toxic materials from fly ash. The other possible disadvantage is the need for a wide operational area, which is unsuitable for densely populated countries. As wet-separation processes have some disadvantages, an improved and/or sustainable alternative recovery technique is required. An air classifier is one of the alternative techniques. In this study, two types of air classifiers, namely a closed-type pneumatic separator and a micron separator, have been investigated. In terms of separation efficiency, it was found that the micron separator has the potential to be applied in cenospheres recovery from coal fly ash, giving a Newton&apos;s efficiency of 0.44, as compared to a value of about 0.26 for the closed-type pneumatic separator. The cenospheres recoveries of both pieces of equipment at their optimum Newton&apos;s efficiencies were similar at over 60 wt.%. The separation performance was further assessed from the particle distributions of the overflow and underflow products obtained from both pieces of equipment, as well as from SEM images. It was found that the lower Newton&apos;s efficiency of the closed-type pneumatic separator was due to the re-concentration of fine particles in the underflow product at air-flow rates higher than 2.2 m/s (the underflow product yield was about 55 wt.%).
    In order to further confirm the applicability of this technique, the micron separator, which had provided higher separation efficiency and cenospheres recovery, was deployed in a cenospheres recovery unit prior to the use of a wet-separation process (float and sink tank). About 80% of the cenospheres was recovered, with an 87.8% reduction in the total mass of fly ash to be separated in the float and sink tank. Consequently, much less water was needed for the process of cenospheres recovery. Moreover, it was also confirmed that the micron separator could yield higher quality fly ashes, that is. fly ash types I and II, from lower feed quality of fly ash type IV, which is the lowest category in commercial classification of fly ash according to JIS A6201. (C) 2010 Elsevier B.V. All rights reserved.

    DOI

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    40
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  • The effect of hydrothermal dewatering of Pontianak tropical peat on organics in wastewater and gaseous products

    Anggoro Tri Mursito, Tsuyoshi Hirajima, Keiko Sasaki, Satoshi Kumagai

    FUEL   89 ( 12 ) 3934 - 3942  2010年12月  [査読有り]

     概要を見る

    This paper describes a study of the effects of hydrothermal dewatering of raw tropical peat from Pontianak, West Kalimantan-Indonesia, on the amounts of organic compounds released into and gaseous products. Hydrothermal upgrading and dewatering of the peat was carried out in a batch-type autoclave reactor at temperatures between 150 and 380 degrees C at a maximum pressure of 25.1 MPa for 30 min. It was found that the extent of decomposition of organics during hydrothermal dewatering depended on temperature increase.
    Wastewater from hydrothermal dewatering was found to contain organic carbon (TOC) ranging from 800 ppm at low temperatures, to 7504 ppm at high temperatures. A number of sugars and furans were detected in the wastewater at 250 degrees C, and organic acids and alcohols at all temperatures. Phenol and phenolic derivatives were observed at 250 degrees C, and significant amounts of CO(2), CO and H(2) were detected at all temperatures studied; CH(4) was detected only at 380 degrees C, but at this temperature CO(2) was no longer detected.
    A simplified schematic diagram of the decomposition behavior of tropical peat in the hydrothermal dewatering process is discussed with respect to the change in the concentration of organics in wastewater and gaseous products as determined by TOC, GC, GC-MS and (13)C NMR analyses of the solids produced. (C) 2010 Elsevier Ltd. All rights reserved.

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    57
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  • Production of Solid Biofuel from Agricultural Wastes of the Palm Oil Industry by Hydrothermal Treatment

    Ahmad T. Yuliansyah, Tsuyoshi Hirajima, Satoshi Kumagai, Keiko Sasaki

    WASTE AND BIOMASS VALORIZATION   1 ( 4 ) 395 - 405  2010年12月  [査読有り]

     概要を見る

    In this study, upgrading of agricultural waste, in the form of oil palm fronds and trunks, into solid biofuel was investigated using hydrothermal treatment. A slurry of 300 mL of water and 30 g of material was treated in a 500-mL batch autoclave equipped with stirrer, thermometer, and pressure sensor. Experiments were conducted in the temperature range 200-350 degrees C at an initial pressure of 2.0 MPa. The slurry was gradually heated to the target temperature and held for a further 30 min. Approximately 35-65% of the original material was recovered as a solid product with favorable solid fuel characteristics. The gross calorific value ranged from 19.9 to 29.7 MJ/kg and the equilibrium moisture content was 7.6-4.5 wt%. The carbon content varied from 51.4 to 78.5 wt% and the oxygen content was 42.1-16.1 wt% after upgrading. Changes in the solid composition and carbon functional groups following upgrading were identified by FTIR and C-13 NMR. In addition, analyses on the liquid product (by GC-MS) and the gas product (by GC) were carried out to clarify the decomposition behavior of material.

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    71
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  • Characterization of secondary arsenic-bearing precipitates formed in the bioleaching of enargite by Acidithiobacillus ferrooxidans

    K. Sasaki, K. Takatsugi, K. Kaneko, N. Kozai, T. Ohnuki, O. H. Tuovinen, T. Hirajima

    HYDROMETALLURGY   104 ( 3-4 ) 424 - 431  2010年10月  [査読有り]

     概要を見る

    The purpose of this study was to characterize secondary minerals that were formed in the bioleaching of enargite (Cu(3)AsS(4)) by Acidithiobacillus ferrooxidans. Two parallel cultures were used: one was adapted to arsenic in the growth medium and the other was wild-type. The progress of the solubilization of As in A. ferrooxidans cultures was stepwise and different from that observed in the non-adapted culture. In contrast, the bioleaching of Cu and Fe from enargite was not affected by prior adaptation of the culture. Minor presence of jarosite was observed by X-ray diffraction (XRD) in solid residues after the bioleaching, and no other peaks of secondary crystalline minerals were detected. The relative intensities of As 3d and Fe 2p to Cu 2p in X-ray photoelectron spectroscopy (XPS) for the solid residues were at maximum at 46 days after the bioleaching with As-adapted A. ferrooxidans. The results from the examination of solid residues with XPS, transmission electron microscopy with energy-dispersive microprobe (TEM-EDS) and XRD after 46 days of contact with As-adapted A. ferrooxidans showed the presence of metastable, amorphous ferric arsenate as an intermediate on the surface of enargite and minor amounts of jarosite. The amorphous ferric arsenate phase did not appear to have an adverse effect of the dissolution of Cu from enargite. Crown Copyright (c) 2010 Published by Elsevier B.V. All rights reserved.

    DOI

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    28
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  • Adhesion of Ferroplasma acidiphilum onto pyrite calculated from the extended DLVO theory using the van Oss-Good-Chaudhury approach

    Mohsen Farahat, Tsuyoshi Hirajima, Keiko Sasaki

    JOURNAL OF COLLOID AND INTERFACE SCIENCE   349 ( 2 ) 594 - 601  2010年09月  [査読有り]

     概要を見る

    The adhesion behavior of Ferroplasma acidiphilum archaeon to pyrite mineral was investigated experimentally and theoretically. F. acidiphilum showed high affinity to adhere to pyrite surface at acidic regions, however low affinity was observed at neutral and alkaline regions. The microbe-mineral adhesion was assessed by the extended DLVO theory. Hamaker constants, electron donors, electron acceptors and surface charges for the microbe and the mineral were experimentally determined. The extended DLVO theory was used to explain the adhesion results. Significant changes to the pyrite surface properties after being treated with the microbial cells were observed. Pyrite lost its hydrophobic nature and became hydrophilic, the contact angle of untreated pyrite was 61 degrees and this decreased to 36 degrees after the treatment. As a consequence, the flotation experiment results showed that F. acidiphilum strain could act as a good depressant for pyrite in xanthat flotation; where in absence of F. acidiphilum cells, over 95% of pyrite can be recovered as a float. However, when the mineral was pretreated with F. acidiphilum cells, less than 20% can be recovered as a float. (C) 2010 Elsevier Inc. All rights reserved.

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    37
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  • Evaluation of processes controlling the geochemical constituents in deep groundwater in Bangladesh: Spatial variability on arsenic and boron enrichment

    M. A. Halim, R. K. Majumder, S. A. Nessa, Y. Hiroshiro, K. Sasaki, B. B. Saha, A. Saepuloh, K. Jinno

    JOURNAL OF HAZARDOUS MATERIALS   180 ( 1-3 ) 50 - 62  2010年08月  [査読有り]

     概要を見る

    Forty-six deep groundwater samples from highly arsenic affected areas in Bangladesh were analyzed in order to evaluate the processes controlling geochemical constituents in the deep aquifer system. Spatial trends of solutes, geochemical modeling and principal component analysis indicate that carbonate dissolution, silicate weathering and ion exchange control the major-ion chemistry. The groundwater is dominantly of Na-Cl type brackish water. Approximately 17% of the examined groundwaters exhibit As concentrations higher than the maximum acceptable limit of 10 mu g/L for drinking water. Strong correlation (R(2) = 0.67) of Fe with dissolved organic carbon (DOC) and positive saturation index of siderite suggests that the reductive dissolution of Fe-oxyhydroxide in presence of organic matter is considered to be the dominant process to release high content of Fe (median 0.31 mg/L) in the deep aquifer. In contrast, As is not correlated with Fe and DOC. Boron concentration in the 26% samples exceeds the standard limit of 500 mu g/L, for water intended for human consumption. Negative relationships of B/Cl ratio with Cl and boron with Na/Ca ratio demonstrate the boron in deep groundwater is accompanied by brackish water and cation exchange within the clayey sediments. (C) 2010 Elsevier B.V. All rights reserved.

    DOI

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    71
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  • Recovery of cenospheres from coal fly ash using a dry separation process: Separation estimation and potential application

    Tsuyoshi Hirajima, H. T. B. M. Petrus, Yuji Oosako, Moriyasu Nonaka, Keiko Sasaki, Takashi Ando

    INTERNATIONAL JOURNAL OF MINERAL PROCESSING   95 ( 1-4 ) 18 - 24  2010年07月  [査読有り]

     概要を見る

    The degree of separation in the recovery of cenospheres from coal fly ash has been estimated for both wet and dry separation processes by applying the terminal velocity concept of particles. Particle diameter and density were determined by sieving industrial cenospheres and coal fly ash type IV, the model particles. This information was then utilized to calculate the terminal velocity needed to estimate the separation performances of both the wet and dry separation processes. Based on this estimation, the dry separation process performed similarly to the wet separation process, with an optimum Newton&apos;s efficiency of 0.54, only slightly lower than that of the wet separation process of 0.6. Moreover, it was observed that the cenospheres were concentrated in the underflow product, whereas for the wet separation process the reverse was true. The findings of this assessment were verified using a micron separator. Similar tendencies in the concentration of cenospheres in the underflow products were obtained. An optimum Newton&apos;s efficiency as high as 0.44 was achieved, with 66% recovery of the cenospheres. The recovery of the cenospheres was only 4% lower than the estimated value (70%), from which we conclude that dry separation processes are interesting technologies to apply to the recovery of cenospheres from coal fly ash because of their high efficiencies. (C) 2010 Elsevier B.V. All rights reserved.

    DOI

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    67
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  • Upgrading and dewatering of raw tropical peat by hydrothermal treatment

    Anggoro Tri Mursito, Tsuyoshi Hirajima, Keiko Sasaki

    FUEL   89 ( 3 ) 635 - 641  2010年03月  [査読有り]

     概要を見る

    In this study, hydrothermal upgrading and dewatering of raw tropical peat derived from Pontianak, West Kalimantan-Indonesia was evaluated at temperatures ranging from 150 to 380 degrees C, a maximum final pressure of 25.1 MPa and a residence time of 30 min. The moisture content of the raw peat was approximately 90 wt.%. Raw peat was hydrothermally upgraded without the addition of water in the laboratory scale. The yield of the solid products was between 53.0 and 99.7 wt.% and the effective calorific value of hydrothermally dewatered peat was between 17,290 and 29,209 kJ/kg following hydrothermal upgrading. In addition, the oxygen content in the solid product was varied from 38.4 to 15.6 wt.% after upgrading, while the carbon content from 55.2 to 77.8 wt.%. The hydrothermally upgraded peat fuel product also had an equilibrium moisture content of 2.3 wt.% and a maximum equilibrium moisture content of 17.6 wt.%. Upgraded peat is characteristically resistant to moisture adsorption at high humidity, which makes it promising for fuel based combustion. The change in the carbon-functional groups and their properties, as determined by FTIR and C-13 NMR, are discussed in terms of the hydrothermal upgrading and dewatering process. (C) 2009 Elsevier Ltd. All rights reserved.

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  • Biooxidation and precipitation for iron and sulfate removal from heap bioleaching effluent streams

    Pauliina Nurmi, Bestamin Ozkaya, Keiko Sasaki, Anna H. Kaksonen, Marja Riekkola-Vanhanen, Olli H. Tuovinen, Jaakko A. Puhakka

    HYDROMETALLURGY   101 ( 1-2 ) 7 - 14  2010年02月  [査読有り]

     概要を見る

    Effluents from bioleaching processes cause severe problems if dispersed in the environment since they typically have very low pH values and high sulfate and ferric iron concentrations. Dissolved iron may also interfere with the metal recovery. In the bioleaching circuit, partial removal of dissolved iron and sulfate is needed to alleviate process disturbances. In this study, an integrated, bench-scale process comprising a fluidized-bed reactor (FBR) and a gravity settler was developed for controlled biological oxidation of ferrous iron and precipitative removal of ferric iron and sulfate for use in waste management of heap bioleaching processes. The FBR for iron oxidation by an enrichment culture dominated by Leptospirillum ferriphilum was operated at 37 +/- 2 degrees C. The FBR recycle liquor was partially neutralized with 10 M KOH or 50 g/L CaCO(3) slurry to promote ferric iron and sulfate precipitation. With 6 +/- 1.5 g Fe(2+)/L in the feed and KOH-adjusted pH 3.5, the oxidation rate of Fe(2+)/L was 3.7 g/L h and 99% precipitation of ferric iron was achieved in the process. Adjustment with CaCO(3) to pH 3.2 slightly decreased the oxidation rate to 3.3 g/L h and 98% of ferric iron precipitated. With 15 g Fe(2+)/L in the feed, the oxidation rate was 7.0 g Fe(2+)/L h coupled with 96% precipitation of ferric iron. A solid solution of jarosite was the main product of ferric iron precipitation with KOH adjustment and with minor amounts of goethite at the higher pH range. Adjustment of the pH with CaCO(3) precipitated ferric iron also as a solid solution of jarosite, and sulfate precipitated also in the form of gypsum (CaSO(4)center dot 2H(2)O) especially at the higher pH values. (C) 2009 Elsevier B.V. All rights reserved.

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    44
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  • 3-90-1 回分式および半回分式処理によるバイオマスの水熱分解性比較(Session 3 バイオマス等,ポスター発表)

    永嶋 良薦, 熊谷 聡, Yuliansyah Ahmad T., 笹木 圭子, 平島 剛

    日本エネルギー学会大会講演要旨集   19   186 - 187  2010年

     概要を見る

    Decomposition behavior of each part of oil palm residue (EFB, fiber, trunk, frond) using a hot-compressed water (HCW) at 200°C in batch and semi-batch treatment was examined. As a result, the water insolubles in batch treatment was more than that in semi-batch treatment. On the other hand, in both treatment, most of hemicellulose was solubilized, while most of cellulose remained in the residue. These behaviors did not depend on feed materials. However, in case of lignin, solubilization ratio in batch treatment was less than that in semi-batch treatment.

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  • P-111 加圧熱水流通式反応装置を用いたオイルパーム残渣各部位の水熱分解特性(ポスター1,ポスター発表)

    永嶋 良薦, 熊谷 聡, Yuliansyah Ahmad T., 笹木 圭子, 平島 剛

    バイオマス科学会議発表論文集   5   74 - 75  2010年

     概要を見る

    Decomposition behavior of each part of oil palm residue (EFB, fiber, trunk, frond) using a hot-compressed water (HCW) flow type reactor at 200℃ was examined. Approximately, 40〜60mg% of the samples was decomposed. Particularly, Most of hemicellulose was solubilized, while most of cellulose remained in the residue. These behaviors did not depend on feed materials. However, in case of lignin, solubilization ratio depended on them. That is, lignin in Trunk and Frond was easy to solubilize in comparison with that in EFB and Fiber.

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  • Spectroscopic study on oxidative dissolution of chalcopyrite, enargite and tennantite at different pH values

    Keiko Sasaki, Koichiro Takatsugi, Kazuhiro Ishikura, Tsuyoshi Hirajima

    HYDROMETALLURGY   100 ( 3-4 ) 144 - 151  2010年01月  [査読有り]

     概要を見る

    Chalcopyrite (CuFeS2) occurs sometimes in association with As-bearing copper ores, such as enargite (Cu3AsS4) and tennantite (Cu12As4S13), especially in deep ore bodies. To employ oxidative pretreatment for recovering copper resources from these minerals, it is important to characterize the surface properties of enargite and tennantite as well as chalcopyrite. The minerals were oxidized in 0.013% H2O2 with O-2 bubbling at pH 2.5, and 11 followed by analysis with X-ray photoelectron spectroscopy. Elemental sulfur was formed most significantly at pH 2 in all sulfide mineral samples. Enargite was the most stable under the oxidative conditions. Arsenic in enargite was partly oxidized at pH 5. Substantial proportion of copper in tennantite was oxidized from Cu(I) to Cu(II) at pH 11. The dissolution rate of Cu from tennantite at pH 2 was by far the fastest, and incongruent dissolution of Cu occurred with suppression of As and S in tennantite. These selective differences in the oxidation may be of use in designing a flotation process for separation of these sulfide minerals. (C) 2009 Elsevier B V All rights reserved.

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  • Adhesion of Escherichia coli onto quartz, hematite and corundum: Extended DLVO theory and flotation behavior

    Mohsen Farahat, Tsuyoshi Hirajima, Keiko Sasaki, Katsumi Doi

    COLLOIDS AND SURFACES B-BIOINTERFACES   74 ( 1 ) 140 - 149  2009年11月  [査読有り]

     概要を見る

    The adhesion of Escherichia coli onto quartz, hematite and corundum was experimentally investigated. A strain of E. coli was used that had the genes for expressing protein for silica precipitation. The maximum cell adhesion was observed at pH &lt; 4.3 for quartz and at pH 4.5-8.5 for corundum. For hematite, cell adhesion remained low at all pH values. The microbe-mineral adhesion was assessed by the extended DLVO theory approach. The essential parameters for calculation of microbe-mineral interaction energy (Hamaker constants and acid-base components) were experimentally determined. The extended DLVO approach could be used to explain the results of the adhesion experiments. The effect of E. coli on the floatability of three oxide minerals was determined and the results showed that E. coli can act as a selective collector for quartz at acidic pH values, with 90% of the quartz floated at 1.5 x 10(9) cells/ml. However, only 9% hematite and 30% corundum could be floated under similar conditions. By using E coli and no reagents, it was possible to separate quartz from a hematite-quartz mixture with Newton&apos;s efficiency of 0.70. Removal of quartz from the corundum mixture was achieved by E coli with Newton&apos;s efficiency of 0.62. (C) 2009 Elsevier B.V. All rights reserved.

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    86
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  • Selective Sorption of Co2+ over Ni2+ Using Biogenic Manganese Oxides

    Keiko Sasaki, Takuya Kaseyama, Tsuyoshi Hirajima

    MATERIALS TRANSACTIONS   50 ( 11 ) 2643 - 2648  2009年11月  [査読有り]

     概要を見る

    Preferential sorption of Co2+ ions over Ni2+ ions was achieved using biogenic Mn oxides produced by the Mn-oxidizing fungus Paraconiothyrium sp. WL-2 strain with a maximum selectivity coefficient (alpha(Co)) of 18. The selective sorption was based on different sorption mechanism for Co2+ and Ni2+ and unique properties of biogenic Mn oxides. The octahedral Co2+ ions occupy vacancies of central metal sites and edge sites in the octahedral Mn oxide unit structures of biogenic Mn oxides, where they are immobilized by oxidation to CoOOH by Mn(III). In contrast, Ni2+ ions are sorbed primarily on layer edges at circumneutral pHs without oxidation. Selective sorption of Co2+ over Ni2+ on the biogenic Mn oxides results from more vacant sites, higher Mn(III) contents, and larger specific surface areas compared to synthetic Mn oxides. [doi: 10.2320/matertrans.M-M2009821]

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    15
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  • Selective sorption of cobalt over nickel on biogenic manganese oxides

    Keiko Sasaki, Takuya Kaseyama, Tsuyoshi Hirajima

    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY   237  2009年03月  [査読有り]

  • Selective sorption of Ce(3+) over La(3+) ions on biogenic manganese oxides

    K. Sasaki, T. Kaseyama, T. Hirajima

    BIOHYDROMETALLURGY: A MEETING POINT BETWEEN MICROBIAL ECOLOGY, METAL RECOVERY PROCESSES AND ENVIRONMENTAL REMEDIATION   71-73   633 - 636  2009年  [査読有り]

     概要を見る

    Unique properties of biogenic Mn oxides were applied to a fundamental study of separation and recovery of rare earth elements. Selective sorption of Ce(3+) over La(3+) ions was achieved at neutral pH values using biogenic Mn oxides produced by Paraconiothyrium sp. WL-2 strain. The selective coefficient for Ce(3+) (alpha(Ce)) was Much greater with biogenic and synthetic Mn oxides than those for La(3+) (alpha(La)). Ce(3+) ions were oxidized to CeO(2) by Mn(III, IV) in Mn oxides under anaerobic conditions resulting in the release of Mn(2+) ions, while La(3+) ions were sorbed without a redox reaction. With an increase in coexisting La(3+) ions, sorption of Ce(3+) oil both Mn oxides was significantly suppressed, especially with synthetic Mn oxides. The edges of the structure are competitive sites because of fewer numbers of vacant sites in synthetic Mn oxide layers. The preferential sorption oil the edge sites of Mn oxides is in the order of La(3+) &gt; Ce(3+). These phenomena call be expanded to separation and recovery of other rare earth elements from natural and anthropogenic Sources.

  • BIOLEACHING OF ENARGITE BY ARSENIC-TOLERANT ACIDITHIOBACILLUS FERROOXIDANS

    Keiko Sasaki, Koichiro Takatsugi, Tsuyoshi Hirajima, Naofumi Kozai, Toshihiko Ohnuki, Olli H. Tuovinen

    BIOHYDROMETALLURGY: A MEETING POINT BETWEEN MICROBIAL ECOLOGY, METAL RECOVERY PROCESSES AND ENVIRONMENTAL REMEDIATION   71-73   485 - +  2009年  [査読有り]

     概要を見る

    Acidithiobacillus ferrooxidans was acclimatized to 1000 mg/L arsenic(V) and then used for the bioleaching of enargite (Cu3AsS4) at pH 2. Secondary minerals formed during the bioleaching of enargite were characterized by X-ray diffraction, FT- infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Oxidative dissolution of enargite resulted in the formation of elemental sulfur, arsenate and oxidized sulfur species including jarosites and possibly also schwertmannite at pH 2.

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    5
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  • Immobilization of Arsenic and Manganese in Contaminated Groundwater by Permeable Reactive Barriers Using Zero Valent Iron and Sheep Manure

    Wahyu Wilopo, Keiko Sasaki, Tsuyoshi Hirajima, Toshiro Yamanaka

    MATERIALS TRANSACTIONS   49 ( 10 ) 2265 - 2274  2008年10月  [査読有り]

     概要を見る

    A permeable reactive barriers (PRBs) column test was carried out to remove arsenic (As) and manganese (Mn) from groundwater using zero valent iron (ZVI), sheep manure, compost and woodchips as reactive materials. Arsenic was mainly immobilized through sorption and co-precipitation with iron-bearing minerals, and also possibly precipitation as FeAsO4. The presence of sulfate-reducing bacteria (SRB) in the inoculated column was suggested by decrease of sulfate concentrations and increase of delta S-34 in the effluent. Arsenic was more effective to immobilize in the inoculated than in the sterilized column due to co-precipitation with sulfides formed by reduction of sulfate in addition sorption and/or co-precipitation with carbonates. The Mn was mainly immobilized through adsorption onto compost and ZVI, and partly by precipitation as carbonates. Manganese was more effectively immobilized in the sterilized than in the inoculated column. Since compost is biodegraded, the capability of compost to immobilize Mn 2(+) decreased in the inoculated column. The result demonstrates that As is more effective to immobilize using mixture of sheep manure with ZVI than only ZVI as reactive materials in PRBs. [doi: 10.2320/matertrans.M-MRA2008827]

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    18
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  • Identification of Sulfate- and Arsenate-Reducing Bacteria in Sheep Manure as Permeable Reactive Materials after Arsenic Immobilization in Groundwater

    Wahyu Wilopo, Keiko Sasaki, Tsuyoshi Hirajima

    MATERIALS TRANSACTIONS   49 ( 10 ) 2275 - 2282  2008年10月  [査読有り]

     概要を見る

    Permeable reactive barriers (PRBs) column tests were performed to investigate the contribution of anaerobic microbial community in sheep manure on the removal of As from groundwater. The column was packed with zero valent iron (ZVI), sheep manure, compost, wood chips, glass beads and gravels. All materials were sterilized except for sheep manure that contains anaerobic bacteria. Decrease in sulfate concentration was observed at the maximum rate of 0.26 mmol dm(-3) day(-1). In addition, the sulfur isotopic ratio of delta S-34 increased from the influent (-4.3 parts per thousand) to the effluent (0.2 parts per thousand), suggesting that there was sulfate-reducing activity in the microbial community. Arsenate was more effectively immobilized on ZVI than arsenite. Bacterial community analysis using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) on 16S rRNA sequences suggested that majorities of bacteria were several Clostridium species and one species of Proteobacteria, Geobacter metallireducens GS-15, independently of PRBs column heights. Some of them might have contributed to the removal of arsenic. [doi: 10.2320/matertrans.M-MRA2008826]

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    5
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  • Immobilization of Se(VI) in mine drainage by permeable reactive barriers: column performance

    K. Sasaki, D. W. Blowes, C. J. Ptacek, W. D. Gould

    Applied Geochemistry   23 ( 5 ) 1012 - 1022  2008年05月  [査読有り]

     概要を見る

    The potential for immobilization of Se in mine drainage water using a permeable reactive barrier was investigated by a column study, in which the reactive components were zero valent Fe, municipal leaf compost, sawdust, and wood chips. These components were mixed with silica sand and gravel. Trace amounts of creek sediment were added to serve as a source of anaerobic bacteria. The influent concentration (40 mg L-1) of SeO42 - decreased to less than 2 mg L-1 within one week and to less than 0.014 mg L-1 within 1 month during passage through the column. In the column, the concentrations of SO42 - also were reduced from 620 to 220 mg L-1. After 2 months, cell populations of SO42 --reducing bacteria, estimated using the MPN method, were in the range of 106-107 cells g-1. Isotopic analysis of S showed δ34S = -9.19‰ for the input solution, and δ34S = -4.69‰ for the output solution. This change in isotopic ratio is attributed to the preferential utilization of 32 SO42 - over 32 SO42 - by SO4-reducing bacteria in the column. Geochemical calculations indicate that SeO42 - is stable in the influent water, and that conditions within the column favour reduction of SeO42 - to metallic Se or SeO32 -, and the reduction of SO42 - to S2-. © 2008 Elsevier Ltd. All rights reserved.

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    22
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  • Removal of arsenate in acid mine drainage by a permeable reactive barrier bearing granulated blast furnace slag: Column study

    Keiko Sasaki, Shunsuke Nukina, Wahyu Wilopo, Tsuyoshi Hirajima

    MATERIALS TRANSACTIONS   49 ( 4 ) 835 - 844  2008年04月  [査読有り]

     概要を見る

    Immobilization of arsenate in groundwater impacted by acid mine drainage was investigated using a permeable reactive barrier (PRB) column bearing granulated blast furnace slag (GBFS) to compare with iron granules which are commonly used. Sorption capacity of arsenate onto the GBFS was quite lower than iron granules in the amount of sorbed arsenate per unit surface area of sorbents (mmol/m(2)) at the equilibrium, Q', in two orders of magnitude in batch tests, however, the amount of sorbed arsenate per unit amount of sorbents (mmol/kg) at the equilibrium, Q, were comparative to each other, because of much higher porosity in the GBFS. Results of column performance showed that 15 mg/L of As was decreased to be less than 0.4 mg/L for more than 18 pore volumes (pv) in the GBFS-PRB by sorption, co-precipitation and presumably formation of hydrated calcium arsenate, and less than 0.04 mg/L for more than 17 pv in the iron bearing PRB probably by co-precipitation with iron (oxyhydro)oxides. Additionally 15 mg/L of Mn2+ ions was also decreased to less than 0.3 mg/L and 0.03 mg/L, respectively, in iron bearing and the GBFS bearing PRB columns, probably caused by sorption and precipitation of oxides and carbonates. The GBFS has advantages to compensate its low reactivity with high porosity, to facilitate the industrial handling with low density, and to utilize industrial wastes for more valuable applications, emphasizing a potential of alternative reactive materials instead of iron granules in PRB for immobilization of arsenic and manganese in acid mine drainage.

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    14
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  • Optimum pH for oxidation of Mn(II) ions in model and actual manganese drainages by a Mn-oxidizing fungus, Phoma sp. strain KY-1

    Keiko Sasaki, Hideki Tachibana, Yuuki Ogawa, Hidetaka Konno

    MATERIALS TRANSACTIONS   49 ( 4 ) 845 - 849  2008年04月  [査読有り]

     概要を見る

    A Mn-oxidizing fungus, Phoma sp. strain KY-1, showed a Mn-oxidizing activity of more than 1.82 mol m(-3) of Mn(II) at an optimum pH 6.8. Controlling the pH at between 6.5 and 7.3 was necessary for fungal oxidation of Mn(II). This is probably due to inactivation of the Mn-oxidizing enzyme by decrease in pH during the reaction. Carbon fiber was found to catalyze the oxidation of Mn(II), most significantly under more unfavorable conditions such as high Mn concentrations, coexisting inhibitive components, or lacking nutrients. Examinations of fungus used for actual Mn-rich mine drainage containing more than 1.46 mol m(-3) of Mn showed that organic nourishments and pH-buffering agents are both essential to obtain acceptable Mn removal rates and that the time required to attain the 10 mg dm(-3) (0.182 mol m(-3)), which is the maximum acceptable concentration of Mn in discharged wastewater in Japan, was about 170 h in the presence of carbon fiber.

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    3
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  • Adsorption of SIP E. coli onto quartz and its applications in froth flotation

    Mohsen Farahat, Tsuyoshi Hirajima, Keiko Sasaki, Yuuki Aiba, Katsumi Doi

    MINERALS ENGINEERING   21 ( 5 ) 389 - 395  2008年04月  [査読有り]

     概要を見る

    Zeta potential measurements of silica-induced protein (SIP) Escherichia coli and quartz showed that the former are positively charged under acidic condition and negatively charged under neutral and alkaline conditions, with an isoelectric point (IEP) at pH 4.5, while the quartz was always negatively charged. Adsorption experiments with bacteria cells on quartz were conducted under different conditions. The results show that at pH values lower than the IEP of the cells, more cells were adsorbed due to electrostatic forces. However, at pH &gt; 4.5, the amount of adsorbed cells decreased as a result of electrostatic repulsion forces. Zeta potentials of quartz showed that at pH 2.5 a significant change in the surface chemistry of quartz occurred after bacterial treatment. The degree of this change was related to the initial SIP E. coli concentration; at 5 x 10(7) cells/ml the average zeta potential of biotreated quartz shifted from -30 mV to 0 mV and at higher concentrations the zeta potential shifted to the positive direction and reached a similar value to that of the bacterial cells. SIP E. coli showed hydrophobic properties at pH lower than the IEP, with approximately 60% of the cells moving to the organic phase from aqueous phase. Bioflotation of quartz using SIP E coli alone at pH 2.5 gave approximately 60% recovery because at this pH more bacteria adsorb onto the quartz surface and the bacterial surface is hydrophobic. In anionic flotation of quartz using sodium dodecyl sulfate, SIP E. coli cells act as a surface modifier, with an increase in flotation recovery from 28% to 85%. This is because the bacterial cells confer hydrophobic properties to the quartz and the biotreated quartz is positively charged, so a large amount of the collector was adsorbed and the recovery increased. (C) 2007 Elsevier Ltd. All rights reserved.

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  • Sorption of Co2+ ions on the biogenic mn oxide produced by a Mn-oxidizing fungus, Paraconiothyrium sp. WL-2

    Keiko Sasaki, Minoru Matsuda, Tomohiro Urata, Tsuyoshi Hirajima, Hidetaka Konno

    MATERIALS TRANSACTIONS   49 ( 3 ) 605 - 611  2008年03月  [査読有り]

     概要を見る

    A Paraconiothyrium sp. WL-2 of Mn-oxidizing fungus is highly tolerant to Mn2+ ions, and capable of oxidizing more than 380 mg dm(-3) of Mn2+ ions, leading to the formation of a large amount of insoluble Mn(III, IV) oxides. The biogenic Mn oxides were characterized by X-ray diffraction, FT-Infrared spectroscopy, elemental analysis, measurement of specific surface area, scanning electron microscopy, and measurement of zeta potential, in comparison with the synthetic Mn oxides. It was found that the biogenic Mn oxide is poorly crystalized birnessite, with higher porosity and much more weakly bounded Mn(II) on the surface than the synthetic Mn oxide. Cobalt(II) ions were sorbed and incorporated as Co(III) into the structure of the biogenic Mn oxide. Sorption efficiency in the biogenic Mn oxide was 5.6 times as high as that in the synthetic ones. Relation of the relased Mn2+ ions to the immobilized Co suggested that Mn(IV) is preferentially used as oxidants over Mn(III) in the biogenic Mn oxide, and emphasized that the existence of Mn(III) in the biogenic Mn oxide activates the geochemical cycles of Mn and the other involved elements in environments.

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  • 島根県三瓶温泉のマンガン沈殿物生成過程における微生物の関与

    阪本 篤史, 石橋 純一郎, 上島 佳貴, 笹木 圭子

    日本地球化学会年会要旨集   55   140 - 140  2008年

     概要を見る

    島根県中部の三瓶山南麓の三瓶温泉では、Fe2+を0.9-6.9ppm, Mn2+を1.1-1.6ppm溶存している最高39.0℃の温泉が湧出しており、温泉湧出口付近では鉄沈殿物(Fe=68.9-79.4%)とマンガン沈殿物(Mn=71.3-79.2%)が分布している。この温泉湧出口から東に20-100m離れた崖沿いの数十箇所からは鉱泉水はMn2+を最大0.6ppm溶存している(Fe2+は検出限界以下)11.8-20.1℃の鉱泉が湧出しており、鉱泉が流れる岩肌にマンガン沈殿物(Mn=0.48-80.9%)が分布しているのが認められる。本研究では、これらの沈殿物、温泉水、鉱泉水の詳細な化学分析結果を報告し、沈殿物の熱力学的および微生物学的生成過程を考察する。

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  • Precipitation of cu-sulfides by copper-tolerant Desulfovibrio isolates

    Olia V. Karnachuk, Keiko Sasaki, Anna L. Gerasimchuk, Olga Sukhanova, Denis A. Ivasenko, Anna H. Kaksonen, Jaakko A. Puhakka, Olli H. Tuovinen

    GEOMICROBIOLOGY JOURNAL   25 ( 5 ) 219 - 227  2008年  [査読有り]

     概要を見る

    The purpose of this work was to isolate Cu-tolerant sulfate-reducers that could be used to produce copper sulfides under pure culture conditions. Three sulfate-reducing bacteria were isolated from wastewater effluents of a zinc-smelter in the Urals and their tolerance to copper varied between 325 and 2600 mg Cu l(-1). Analysis of 16S rRNA gene sequences placed the isolates in the genus Desulfovibrio. The isolates showed pronounced saccharolytic growth. Growing cultures precipitated Cu2+ as covellite (CuS) within less than a week. Extended incubation for 1 month lead to the formation of chalcocite (Cu2S) and chalcopyrite (CuFeS2).

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  • Spectroscopic study of precipitates formed during removal of selenium from mine drainage spiked with selenate using permeable reactive materials

    Keiko Sasaki, David W. Blowes, Carol J. Ptacek

    GEOCHEMICAL JOURNAL   42 ( 3 ) 283 - 294  2008年  [査読有り]

     概要を見る

    The potential for Se removal from mine drainage water using permeable reactive materials was evaluated by a laboratory column experiment. The column materials, organic carbon and zero valence iron (ZVI), were exposed to mine drainage containing 630 mg L-1 SO42-. The influent water was spiked with 40 mg L-1 Se(VI) to assess the potential for Se removal. This high Se(VI) concentration was selected to ensure that there would be a sufficient mass of Se-bearing reaction products available for mineralogical characterization. The experiment was conducted in an anaerobic chamber to replicate the anaerobic conditions that prevail in permeable reactive barrier systems. After loading 10.8 pore volumes of input solution, the column effluent contained &lt;0.002 mg L-1 Se and &lt;300 mg L-1 SO42-. After the column experiments was complete the reactive materials were sampled in the anaerobic chamber and examined using scanning electron microscopy (SEM) coupled with energy dispersion X-ray analysis (SEM-EDAX), X-ray photoelectron spectroscopy (XPS) and by Raman spectroscopy. Sulfate was reduced to sulfide and elemental sulfur, which accumulated on the surfaces of the column materials. Se-bearing precipitates were observed at the base of column. Scanning electron microscopy (SEM) showed the presence of elemental Se, suggesting that Se(VI) was partly reduced to metallic Se(0). The XPS results revealed that selenate was reduced mainly to iron selenide (FeSe and/or FeSe2) on the surface of the column substances. These observations suggest that both chemical reduction and biologically mediated reduction of Se(VI) occurred.

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  • 水熱処理によるバイオマス・低品位炭混合燃料化での分解抽出挙動

    野中 壯泰, 平島 剛, 廣瀬 歩美, 笹木 圭子

    Journal of MMIJ : journal of the Mining and Materials Processing Institute of Japan   123 ( 11 ) 532 - 536  2007年11月

     概要を見る

    A fundamental investigation on the extraction from biomass, low rank coal and their mixture during hydrothermal treatment was conducted by using a circulative equipment having a 10 cm3 cell. Beluga coal from Alaska, and Cryptomeria Japonica and empty fruit bunch of oil palm (EFB) were used as material samples of low rank coal and biomass, respectively. Biomass started to be decomposed at a temperature lower than that of low rank coal, which suggests that amorphous cellulose and hemicellulose were hydrolyzed. Frans such as furfural and 5-hydroxymethyl-2-furaldehyde (HMF) extracted from biomass were unstable as compared to phenol, and therefore decomposed and partially cyclized. It was considered that low rank coal adsorbed extracts from biomass due to the porous morphology. The possibility to predict the TOC from an on-line monitoring of the absorbance intensity in UV region during hydrothermal treatment was also shown.

    DOI CiNii

  • 7-9 石炭飛灰からの中空球形微粒子の回収((5)廃棄物有効利用または資源循環,Session 7 環境対策・リサイクル,研究発表(口頭発表))

    平島 剛, 大迫 雄司, 野中 壯泰, 笹木 圭子, 安藤 隆

    日本エネルギー学会大会講演要旨集   16   326 - 327  2007年

    DOI CiNii

  • 3-40 水熱処理による低品位炭とバイオマスの高品位混合燃料化((11)水熱反応1,Session 3 バイオマス等,研究発表(口頭発表))

    平島 剛, 野中 壯泰, 笹木 圭子, 鶴井 雅夫, 土屋 富士夫

    日本エネルギー学会大会講演要旨集   16   178 - 179  2007年

    DOI CiNii

  • Sorption of co ions on biogenic mn oxides procuced by a Mn-oxidizing fungus, Paraconiothyrium sp.-like strain

    K. Sasaki, M. Matsuda, T. Urata, T. Hirajima, H. Konn

    BIOHYDROMETALLURY: FROM THE SINGLE CELL TO THE ENVIRONMENT   20-21   607 - +  2007年  [査読有り]

     概要を見る

    Sorption of Co(II) on the biogenic Mn oxide produced by a Paraconiothyrium sp.-like strain was investigated. The biogenic Mn oxide, which was characterized to be poorly crystalline birnessite ((Na4Mn6Mn(IV))-Mn-(III) O-8(27)center dot 9H(2)O) bearing Mn(III) and Mn(IV) in the structure, showed approximately 6.0-fold higher efficiency for Co(II) sorption than a synthetic Mn oxide. XP-spectra of Co 2p for the biogenic and synthetic Mn oxides after Co(II) sorption indicate that Co was immobilized as Co(III) on the surface of Mn oxides, clearly suggesting that redox reaction occurs between Co(II) ions and each Mn oxides, The Co(II) ions would be initially sorbed on the vacant sites of the surface of biogenic Mn oxide, and then oxidized to Co(III) by neighbor Mn(III/IV) atoms to release Mn(II). For the synthetic Mn oxide, release of Mn(II) was negligibly small because the oxidant is only Mn(IV) in ramsdellite (gamma-MnO2). The Mn(II) release from the biogenic Mn oxide during Co(II) adsorption would be not only from weakly bounded Mn(II), but also from redox reaction between Mn(III/IV) and Co(II) ions.

  • Singular effect of carbon fiber on the oxidation of dissolved Mn(II) ions by a fungus genetically related to Phoma sp.

    Hidetaka Konno, Keiko Sasaki, Yuuki Ogawa, Hideki Tachibana

    MATERIALS TRANSACTIONS   48 ( 1 ) 64 - 67  2007年01月  [査読有り]

     概要を見る

    Oxidation of Mn(II) ions in model drainages by a fungus genetically related to Phoma sp. was carried out in the presence of polyacrylonitrile-based carbon fiber, pitch-based carbon fibers formed at different heat treatment temperatures, and bamboo charcoal, aiming to understand the morphological effect of carbon materials on the microbiological activity of the manganese-oxidizing fungus. From the experimental results obtained so far, it was reasonably concluded that only carbon fiber accelerates the oxidation of dissolved Mn(II) ions by this fungus. When the carbon fiber shortened below certain length, the promoting effect was lost. The results strongly suggest that the shape of carbon, specifically the fibrous shape having flexibility, is a crucial factor in the promoting effect on the manganese oxidation by the present fungus.

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  • Formation of Ni- and Zn-sulfides in cultures of sulfate-reducing bacteria

    Jonathan P. Gramp, Jerry M. Bigham, Keiko Sasaki, Olli H. Tuovinen

    GEOMICROBIOLOGY JOURNAL   24 ( 7-8 ) 609 - 614  2007年  [査読有り]

     概要を見る

    The purpose of this study was to characterize Ni- and Zn-sulfides precipitated in sulfate-reducing bacterial cultures. Fe-free media containing 58 mM SO42- were amended with Ni and Zn chloride followed by inoculation. Precipitates were sampled from cultures after two weeks of incubation at 22, 45, and 60 degrees C. Abiotic controls were prepared by reacting bacteria-free liquid media with Na2S solutions under otherwise identical conditions. Precipitates were collected anaerobically, freeze-dried and analyzed by x-ray diffraction (XRD), scanning electron microscopy, and for total Ni, Zn, and S. In Ni-containing media, biogenic sulfide precipitates were mostly heazelwoodite (Ni3S2), whereas abiotic precipitates were mixed heazelwoodite and vaesite (NiS2). The biogenic Ni-precipitates were better crystalline than the corresponding abiotic samples. Sphalerite (ZnS) was identified by XRD in precipitates sampled from Zn-containing media. Scanning electron microscopy revealed disordered morphological features for the sulfides, which occurred mostly as aggregates of fine particles in biogenic samples, whereas abiotic precipitates contained more plate- and needle-like structures.

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  • Phylogenetic analysis of manganese-oxidizing fungi isolated from manganese-rich aquatic environments in Hokkaido, Japan

    Keishi Takano, Yasoo Itoh, Tagiru Ogino, Kunihiko Kurosawa, Keiko Sasaki

    LIMNOLOGY   7 ( 3 ) 219 - 223  2006年12月  [査読有り]

     概要を見る

    Three strains of Mn-oxidizing fungi were isolated from manganese-rich aquatic environments: sediment in a stream (Komanoyu) in Mori-machi and inflow to an artificial wetland in Kaminokuni-cho, Hokkaido, Japan. The characteristics of each strain were then established. Genetic analysis based on the ribosomal RNA (rRNA) gene was performed to clarify their classification. The sequences of the 18S rRNA and internal transcribed spacer (ITS1)-5.8S rRNA-ITS2 genes showed that all three strains are Ascomycetes. Based on its morphology, it seems probable that the KY-1 strain from Mori-machi belongs to the genus Phoma or Ampelomyces. The phylogenetic analysis indicates that this strain belongs to Phoma rather than Ampelomyces. Morphological identification of WL-1 and WL-2 strains from Kaminokuni-cho was impossible because of the lack of a sexual stage and specific organs. Phylogenetic analysis of the sequence in the ITS1-5.8S rRNA-ITS2 gene suggests that the WL-1 strain corresponds to Paraconyothyrium. sporulosum? and that WL-2 also belongs to the genus Paraconiothyrium. Because the ability to oxidize Mn has not been evaluated for most species of Phonza or Paraconiothyrium (Coniothyrium), further study is needed to confirm the status of these three strains.

    DOI

  • Formation of covellite (CuS) under biological sulfate-reducing conditions

    Jonathan P. Gramp, Keiko Sasaki, Jerry M. Bigham, Olia V. Karnachuk, Olli H. Tuovinen

    GEOMICROBIOLOGY JOURNAL   23 ( 8 ) 613 - 619  2006年12月  [査読有り]

     概要を見る

    Sulfate-reducing bacteria (SRB) play a major role in the precipitation of metal sulfides in the environment. In this work, biogenic copper sulfide formation was examined in cultures of SRB and compared to chemically initiated Cu sulfide precipitation as a reference system. Mixed cultures of SRB were incubated at 22, 45, and 60 degrees C in nutrient solutions that contained copper sulfate. Abiotic reference samples were produced by reacting uninoculated liquid media with Na2S solutions under otherwise identical conditions. Precipitates were collected anaerobically by centrifugation, frozen in liquid N-2, and freeze-dried, followed by analysis using X-ray diffraction (XRD), X-ray fluorescence, and scanning electron microscopy. Covellite (CuS) was the only mineral found in the precipitates. Covellite was less crystalline in the biogenic precipitates than in the abiotic samples based on XRD peak widths and peak to background ratios. Poor crystallinity may be the result of slower precipitation rates in bacterial cultures as compared to the abiotic reference systems. Furthermore, bacterial cells may inhibit the nucleation steps that lead to crystal formation. Incubation at elevated temperatures improved the crystallinity of the biotic specimens.

    DOI

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    40
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  • ベンチスケール連続式水熱処理装置によるバイオマス・低品位炭混合燃料の製造

    野中 壯泰, 平島 剛, 柿添 亮平, 笹木 圭子, 土屋 富士雄, 鶴井 雅夫

    資源と素材 : 資源・素材学会誌   122 ( 10 ) 522 - 527  2006年11月

     概要を見る

    Hydrothermal treatments of mixtures of Beluga coal and Cryptomeria Japonica were conducted by using a slurry of 10wt% density, fed at 10 kg/h rate in the reactor of a bench-scale continuous equipment, the temperature and pressure of which were set at 300°C and 12 MPa, respectively. The reaction time was 30 minutes. It was found that, during the hydrothermal treatment, the yield of solid phase decreased and the total organic carbon (TOC) of liquid phase increased as the biomass-mixing ratio increased. That means that the biomass was more decomposable than the coal. Besides, volatile matter in the material sample showed a higher decomposability, as compared with fixed carbon, and part of the decomposed volatile matter was considered to produce new aromatic compounds and carboxylic acids through repolymerization to fixed carbon. As a consequence, the gross calorific value of the solid phase of the hydrothermally treated mixture became higher with increasing biomass-mixing ratio on a dry basis. Considering ash content, the solid phase showed negligible change in gross calorific value, independent of the mixing ratio; it was ca. 7300 kcal/kg on a dry ash-free basis. In addition, it is worth mentioning that a five-hour run using a bench-scale continuous equipment was conducted successfully.

    DOI CiNii

  • Immobilization of Mn(II) ions by a Mn-oxidizing fungus - Paraconiothyrium sp.-like strain at neutral pHs

    Keiko Sasaki, Minoru Matsuda, Tsuyoshi Hirajima, Keishi Takano, Hidetaka Konno

    MATERIALS TRANSACTIONS   47 ( 10 ) 2457 - 2461  2006年10月  [査読有り]

     概要を見る

    A Mn-oxidizing fungus was isolated from a constructed wetland of Hokkaido (Japan), which is receiving the Mn-impacted drainage, and genetically and morphologically identified as Paraconiothyrium sp.-like strain. The optimum pHs were 6.45-6.64, where is more acidic than those of previously reported Mn-oxidizing fungi. Too much nutrient inhibited fungal Mn-oxidation, and too little nutrient also delayed Mn oxidation even at optimum pH. In order to achieve the oxidation of high concentrations of Mn like mine drainage containing several hundreds g-m(-3) of Mn, it is important to find the best mix ratio among the initial Mn concentrations, inocolumn size and nutrient concentration. The strain has still Mn-tolerance with more than 380 g-m(-3) of Mn, but high Mn(II) oxidation was limited by pH control and supplied nutrient amounts. The biogenic Mn deposit was poorly crystallized birnessite. The strain is an unique Mn-oxidizing fungus having a high Mn tolerance and weakly acidic tolerance, since there has been no record about the property of the strain. There is a potentiality to apply the strain to the environmental bioremediation.

    DOI

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    25
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  • FE-SEM study of microbially formed jarosites by Acidithiobacillus ferrooxidans

    Keiko Sasaki, Takashi Sakimoto, Mai Endo, Hidetaka Konno

    MATERIALS TRANSACTIONS   47 ( 4 ) 1155 - 1162  2006年04月  [査読有り]

     概要を見る

    Morphological characterization of jarosite groups formed from Fe(III) biologically oxidized with different numbers of Acidithiobacillus ferrooxidans was conducted using FE-SEM. The higher population of A. ferrooxidans resulted in more distinct jarosite mineral shape, and stronger Raman intensities for potassium jarosite, ammoniojarosite and argentojarosite. The morphology of the jarosites might he dependent oil iron-oxidizing activity of A. ferrooxidans.
    The technique was applied to identify jarosite compounds formed during microbially mediated dissolution of arsenopyrite by A ferrooxidans. It is difficult to identify this jarosite compound by X-ray diffraction and Raman spectroscopy because amounts are typically low and the crystallization is poor in minerals formed by microbially mediated oxidation. However, FE-SEM image provided helpful information for identification of jarosite compounds.
    The results suggest that morphology would provide useful information for identification and history of jarosite minerals as geochemical samples.

    DOI

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    16
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  • Floatability of rare earth phosphors from waste fluorescent lamps

    T Hirajima, A Bissombolo, K Sasaki, K Nakayama, H Hirai, M Tsunekawa

    INTERNATIONAL JOURNAL OF MINERAL PROCESSING   77 ( 4 ) 187 - 198  2005年12月  [査読有り]

     概要を見る

    Zeta-potential measurements were made to determine the electric state of phosphor materials on the basis of which a feasibility study could be performed for the use of flotation in the recovery of fine (d50 &lt; 13 gm) rare earth phosphors from waste fluorescent lamps. Tests were carried out with pure specimens of white (calcium halo-phosphate), red, green and blue (rare earth) phosphors, with a 17: 1 : 1 : I ratio of their mixture, and with actual waste phosphor materials. The effects of a cationic (dodecyl ammonium acetate, DAA) and two anionic (sodium dodecyl sulfate (SDS) and sodium oleate (NaOl)) collectors on the floatability of materials, as well as that of Na2SiO3 dispersant on the separation characteristics, were investigated at different pH ranges. The process, applied to actual discarded waste phosphors gave, in a two-stage separation scheme, sink products assaying 17.7-23.8% and 21.5-25.9% rare earth phosphors for DAA and SDS flotation, respectively. The recovery and Newton's efficiency were about 70-90% and 0.26-0.37, 66-82% and 0.18-0.20, respectively for DAA and SDS flotation. (c) 2005 Elsevier B.V. All rights reserved.

  • Feasibility of an efficient recovery of rare earth-activated phosphors from waste fluorescent lamps through dense-medium centrifugation

    T Hirajima, K Sasaki, A Bissombolo, H Hirai, M Hamada, M Tsunekawa

    SEPARATION AND PURIFICATION TECHNOLOGY   44 ( 3 ) 197 - 204  2005年08月  [査読有り]

     概要を見る

    Experiments were carried out with waste phosphors collected during the recycling of end-of-life fluorescent lamps to obtain a highly enriched phosphors product as starting material for the better extraction of rare earth elements. The aim of this work was therefore to separate low-density calcium halo-phosphate phosphors from high-density rare earth-activated phosphors through dense-medium centrifugation (with di-iodomethane as organic dense-medium). The feasibility of the process and the conditions for a good separation (higher Newton's efficiency) appear to be a function of the rotation speed of the centrifugal separator, the pulp concentration and the adsorption of a surfactant (sodium oleate, NaOl) during the pre-treatment stage. The effect of the centrifugation time was less pronounced. Through this study, a sink product assaying 48.61% of rare earth-activated phosphors could be recovered from waste phosphor materials pre-treated with 5 x 10(-5) mol/dm(3) of sodium oleate (NaOl) surfactant. The Newton's efficiency and recovery of the separation were 0.84 and 97.34%, respectively. The process feasibility was reinforced by the possibility to recover, through laboratory batch tests, more than 99.8% of the di-iodomethane (CH2I2). (C) 2005 Elsevier B.V. All rights reserved.

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    79
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  • 微生物を媒介としたマンガンの鉱化作用とその環境修復への展望

    笹木 圭子

    資源地質   55 ( 2 ) 195 - 202  2005年

     概要を見る

    Manganese-oxidizing microorganisms are distributed in a wide range of environments. Amorphous biogenic manganese oxides play a significant role in the control of trace phase distribution in aquatic system. Some of them, which are tolerant to extremely high concentrations of Mn and have optimum pH less than 7, can be practically applied to treatment high Mn water, such as Mn-rich mine drainage. Additionally, the biogenic Mn deposits are poorly crystalline and significantly porous, providing highly efficient reaction fields in the environments, which are approached for decomposition and molecular size reduction of organic compounds like humic substances, oxidants, adsorbents of toxic metals, and so on.

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  • Synthesis of aragonite crystals from pulverized scallop shells

    T Hirajima, A Bissombolo, K Sasaki, M Takeucki

    Proceedings of the 8th International Symposium on East Asian Resources Recycling Technology-2005     455 - 459  2005年  [査読有り]

     概要を見る

    Despite the use of scallop shells for soil improvement and as bed materials in oyster cultivation, or as culvert fitting materials and food additive, a huge amount of this waste is stockpiled or discarded to land filling sites every year. Recently, the depletion of land filling sites, the sudden increase in the treatment cost of waste materials and the new environmental regulations are pushing for a continuous improvement of recyclable materials. The synthesis of needle like crystals of aragonite from pulverized scallop shells, mainly made of the calcite form calcium carbonate, to get a product that could be used as filler for plastics, rubber, paper, follows this objective.
    In the present study aimed at the synthesis of crystals of different size and different aspect ratio of the aragonite form calcium carbonate, scallop shells were pulverized, calcined, and then hydrated, to have mainly Ca(OH)(2) as starting material. The conversion of calcite into aragonite form was made by treating in one stage or two stage chemical process the dissolved Ca(OH)(2) with MgCl2 and CO2 at relatively low temperature, 35 degrees C and 60 degrees C respectively. Parameters such as pulp density and pH, MgCl2 concentration, CO2 flow rate and mixing conditions were investigated through the study. SEM and XRD analyses of dried precipitates indicate that crystals of 1.36-12.33 mu m in length and 0.10-0.49 mu m in width, with an aspect ratio of 7.15-25.16 could be obtained by these methods. Besides ultrasonic waves stirring was suggested to prevent synthesized crystals Z aggregating.

  • Removal of Mn(II) Ions from Aqueous Neutral Media by Manganese-Oxidizing Fungus in the Presence of Carbon

    Keiko Sasaki, Hidetaka Konno, Mai Endo, Keishi Takano

    Biotechnology and Bioengineering   85 ( 5 ) 489 - 496  2004年03月  [査読有り]

     概要を見る

    A manganese-oxidizing fungus was isolated from a hot spring in Japan. The fungus was increasingly effective at oxidizing Mn(II) ions as the concentration of organic carbon sources in the growth medium was decreased. The fungus oxidized 50 ppm of Mn(II) ions within 160 h in a pH 7.3 medium at 25°C. The presence of carbon fiber shortened the time to 80 h, and promoted steady oxidation. The oxidation products were identified by XPS and XRD to be poorly crystallized and amorphous MnO2, both with and without the fiber. These results suggest that the fiber participates in kinetically limited oxidation. The fungus was entangled with and clung to the fibers, and the oxidized Mn species accumulated on the fungus. Similarly shaped polyethylene telephthalate fiber did not enhance the oxidation, nor was adhesion of the fungus observed. Although the mechanism is still unknown, the present work shows that removal of Mn from solution through the precipitation and accumulation of Mn-oxides on the fungus in the presence of carbon fiber is a promising improvement for water treatment. © 2004 Wiley Periodicals, Inc.

    DOI PubMed

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  • 水熱処理法による木質系バイオマス燃料製造とその生成液体による Cr(VI) 還元

    小林 弘幸, 平島 剛, 湯川 健太郎, 恒川 昌美, 福嶋 正巳, 笹木 圭子, 大里 克明, 須藤 良考

    資源と素材 : 資源・素材学会誌 : journal of the Mining and Materials Processing Institute of Japan   119 ( 6/7 ) 416 - 422  2003年07月

     概要を見る

    In hydrothermal treatment Cryptomeria Japonica (gymnosperm) was treated at temperatures of 270-330 °C in the presence of liquid water for 30 minutes using an autoclave of 10 L capacity. The solid product having heating values of 7,000-7,200 kcal / kg (dry basis) was obtained at yields of 48-55 %. The FT-IR, proximate and ultimate analysis results of this solid product were similar to those of the solid product obtained by hydrothermal treatment of Acacia Mangium (dicotyledonous angiosperm) reported in our previous paper. The liquid product is composed of mainly methyl alcohol, acetic acid, ...

    DOI CiNii

  • 熱水乾燥法による低品位炭改質時に生成する溶液のキャラクタリゼーションとそのCr(VI)還元能

    湯川 健太郎, 平島 剛, 恒川 昌美, 須山 千秋, 笹木 圭子, 福嶋 正巳, 小林 弘幸, 平井 智

    資源と素材 : 資源・素材学会誌 : journal of the Mining and Materials Processing Institute of Japan   119 ( 4/5 ) 161 - 169  2003年05月

     概要を見る

    Liquid products produced in a hot water drying (HWD) process of Beluga low rank coal were characterized by GC/MS, HPLC, GPC, TOC measurement and cyclic voltammetry. The Beluga coal was treated at three different temperatures, namely 270, 300 and 330°C. The ability of the liquid products to reduce Cr(VI) was investigated by analyzing the solution containing the liquid and Cr(VI), using Fluorescence Spectrometry. With increasing treatment temperature TOC concentration of the liquid products became larger. The liquid product at 270°C contained acetic acid, acetic acid-methyl ester and oligome...

    DOI CiNii

  • Distribution and transition of heavy metals in mine tailing dumps

    K Sasaki, T Haga, T Hirajima, K Kurosawa, M Tsunekawa

    MATERIALS TRANSACTIONS   43 ( 11 ) 2778 - 2783  2002年11月  [査読有り]

     概要を見る

    The vertical distributions of heavy metals and other elements in sediment core samples in a landfill of abandoned mine tailings were examined. Core samples were analyzed by XRF and XRD, and further examined by ICP-AES measurements after acid-sequential extraction with HCl, HE and HNO3. According to XRD, the sediments contained alpha-quartz as the main component, and sericite, chlorite, rhodochrosite. pyrite, jarosite, sphalerite, and galena as minor components. A complete decomposition method using sequential extraction for the mine tailings sediments was established at ambient temperatures. Acid sequential extraction was useful for the analysis of minerals in mine tailings which are difficult to detect by XRD. Rhodochrosite and chlorite were dissolved by HCl-extraction, quartz and sericite by HF-extraction, and sulfides by HNO3-extraction. Rhodochrosite was the main source of high concentrations of Mn in mine drainage, highly distributed below the - 100 cm zone in the mine tailings, combined with pyrite but not with sericite and quartz. The distributions of most heavy metals were related to those of pyrite.

  • 廃ホタテ貝殻焼成物を原料とするaragonite型軽質炭酸カルシウムの合成 -非晶質炭酸カルシウムを中間体とする方法-

    笹木 圭子, 本郷 大, 恒川 昌美

    資源と素材 : 資源・素材学会誌 : journal of the Mining and Materials Processing Institute of Japan   113 ( 12 ) 1055 - 1058  1997年12月

     概要を見る

    Aragonite type of calcium carbonate was synthesized via amorphous calcium carbonate from calcined scallop shell. The effect of aging and Mg2+ ion addition on polymorphism of the product was determined, and the mechanism of formation of aragonite is discussed. Aging of amorphous calcium carbonate first led to the formation of calcite and unstable vaterite, and the vaterite was then converted to aragonite with the longer aging. The addition of Mg2+ ions further enhanced the formation of aragonite. The elemental analysis by atomic absorption spectrometry and the characterization of the products by EPMA and XRD showed that Mg2+ ions were preferentially adsorbed on the calcite nucleus, then involved in the growing calcite (not needlelike crystal like aragonite). This adsorption inhibited the growth of calcite, leading to aragonite formation.

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  • Investigation of copper(II)-binding behavior of fulvic acids by three-dimensional fluorescence spectrometry

    M Fukushima, S Tanaka, K Nakayasu, K Sasaki, H Nakamura, K Tatsumi

    ANALYTICAL SCIENCES   13 ( 6 ) 1011 - 1015  1997年12月

    DOI CiNii

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    14
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  • 酸性環境における黄鉄鉱の溶解及びその抑制に関する研究

    笹木 圭子

    分析化学   46 ( 7 ) 611 - 612  1997年

     概要を見る

    To clarify the formation mechanism of acid mine drainage and to propose a method to alleviate this environmental problem, the microbially-mediated dissolution of pyrite and its suppression was investigated. First, the dissolution of pyrite with the iron-oxidizing bacteria, Thiobacillus ferrooxidans, was investigated by both a solution analysis (ICP-AES) and a mineral-surface analysis (XRD, XPS, FTIR, and XMA). A microbial attack on pyrite by T. ferrooxidans proceeds mainly by the "indirect contact mechanism". An abiotic dissolution of pyrite with Fe(III) ions around pH 2 was found to be suppressed by the complexation of Fe(III) ions with anionic ligands, such as oxalate, and also by a preferential adsorption of Cu(II) and Fe(II) ions. Tannic and fulvic acids were found to be more effective inhibitors of T. ferrooxidans and T. thiooxidans than oxalic acid, reported by others. Finally, originally isolated fulvic acids were used to elucidate the suppression of the microbially mediated dissolution of pyrite by T. ferrooxidans and T. thiooxidans. The suppression was due to the inhibition of microorganisms by organic acids and their adsorption to active sites of the pyrite surface, as well as the reduction and complexation of Fe(III) ions by them. The results indicate that humic substances would be useful for the remediation and prevention of damage caused by acid mine drainage

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  • X-RAY PHOTOELECTRON SPECTROSCOPIC ANALYSIS OF SURFACE PRODUCTS ON PYRITE FORMED BY BACTERIAL LEACHING

    H KONNO, K SASAKI, M TSUNEKAWA, T TAKAMORI, R FURUICHI

    BUNSEKI KAGAKU   40 ( 11 ) 609 - 616  1991年11月  [査読有り]

     概要を見る

    Bacterial leaching is often applied to recover useful metallic elements from low grade ores; an understanding of the leaching mechanism is necessary to improve the efficiency of this process. In the present work, surface analysis by XPS was carried out on pyrite (FeS2) after leaching with Thiobacillus ferrooxidans for 1 to 11 d. The measured complex spectra were analyzed by the concept of differential charging effects; it was found that Fe(II, III), S, SO4(2-), and probably SO3(2-), are formed on the pyrite. The accumulation of K+ ions was also found with more than 6 d of leaching. Although the observed elemental S is considered to be an intermediate product in the indirect leaching mechanism, the formation on pyrite particles during the bacterial leaching has not been directly observed. The assignment of the SO3(2-) peak is still conditional but, as a metabolic intermediate, the formation of SO3(2-) ions in the cell has been proposed by others. The time variations in the mole ratios of species of S or K vs. Fe in the surface products are helpful to understand the leaching mechanism. The accumulation of Fe(III), SO4(2-), K+ and OH- ions on the surface with leaching suggests the formation of insoluble compounds, such as jarosite (chemical formula: K[Fe3(SO4)2(OH)6]).

  • Leaching behavior and its mechanism in the leaching of a chalcopyrite concentrate by Thiobacillus ferrooxidans

    Takamori, Takakatsu, Sasaki, Keiko, Tsunekawa, Masami, Hirajima, Tsuyoshi

    Shigen to sozai   106 ( 4 )  1990年

  • Leaching behavior of a chalcopyrite concentrate in the coexistent system of thiobacillus thiooxidans with thiobaccilus ferroxidans, and phospholipid as extracellular substances

    Takakatsu Takamori, Takuya Yamamoto, Keiko Sasaki, Masami Tsunekawa, Tsuyoshi Hirajima

    Shigen to sozai   106 ( 10 ) 611 - 616  1990年  [査読有り]

     概要を見る

    In the previous report, the authors considered the leaching mechanism of chalcopyrite concentrate by Thiobacillus ferrooxidans, and pointed out that leaching rate was mainly controlled by the deposition of elemental sulphur on the mineral surface. In this report, the effect of the coexistence of Thiobacillus thiooxidans, whose energy source is elemental sulphur, with Thiobacillus ferrooxidans on the leaching of a chalcopyrite concentrate was investigated. During the culture of both species the relation between the surface tension of the culture medium and cell number was examined, and the phospholipid which is one of the extracellular substances in the culture of both microorganisms were qualitatively analyzed by thin layer chromatography. The leaching efficiency of a chalcopyrite was conspicuously improved by the coexistence of Thiobacillus thiooxidans with Thiobacillus ferrooxidans. The results indicated that in order to make efficient the leaching of chalcopyrite concentrate, it is necessary that the reactions of equations (1) to (3) or (4) mentioned in the text must consecutively proceed. However, the initially high leaching rate of chalcopyrite did not continue to the complete dissolution of chalcopyrite. The reason is that the growth of Thiobacillus thiooxidans was depressed by the increase of ferrous ion concentration, and that it became impossible to keep the sequence in the above mentioned reactions. Accordingly it is indicated that in order to improve further the efficiency of leaching it is necessary to artificially control the chemical constituents of the leaching solution. As the cell number increased, the surface tension of the culture medium decreased. Phosphatidylethanolamine and phosphatidylglycerol were detected as phospholipid. The phospholipid is polar-nonpolar substance, accordingly these extracellular substances would affect the leaching rate.

    DOI

    Scopus

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    被引用数
    (Scopus)

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書籍等出版物

  • Nanoscale Materials with Different Dimensions for Advanced Electrocatalysts

    ( 担当: 共著,  担当範囲: ”Nanomaterials for sustainable energy and environmental remediation")

    Elsevier  2020年

  • Microbiology for Minerals, Metals, Materials and Environment,

    笹木 圭子( 担当: 分担執筆)

    CRC Press/ Taylor and Francis.  2014年12月

  • Manganese oxides in Environments

    笹木 圭子( 担当: 共著,  担当範囲: ,)

    American Chemical Society Symposium Series  2014年11月

  • Biology for Minerals, Metals, Materials and Environment

    SASAKI Keiko( 担当: 分担執筆)

    CRC  2014年03月

  • 水の分析 第5版

    笹木 圭子( 担当: 編集)

    化学同人  2005年05月

  • 演習で学ぶ環境

    笹木 圭子( 担当: 共編者(共編著者))

    三共出版  2002年12月

▼全件表示

Works(作品等)

  • 人工湿地の生態系を利用した酸性廃水処理技術の開発研究

    2002年
    -
     

  • 鉱廃水の生物処理に対する炭素材料の応用

    2001年
    -
     

  • 鉱山廃水及び生活用水源からのマンガン除去技術の開発研究

    1999年
    -
    2001年

  • 炭素材料を担体とした微生物によるマンガン資源濃集に関する研究

    2000年
    -
     

講演・口頭発表等

  • nvironmental impact of amino acids on the stability of hydrotalcite after bearing SeO42- intergrated with DFT simulation

    MENGMENG WANG, HIROFUMI AKAMATSU, ISMAILA DABO, KEIKO SASAKI

    Goldschmidt 2021  

    発表年月: 2021年07月

  • Metal-free Porous Carbon Nitride/Poypyrrole/Montmorillonite Nanocomposite for Photocatalytic Mineralization of Metronidazole

    Vellaichamy Balakumar, Keiko Sasaki

    ACS 2021 spring  

    発表年月: 2021年04月

  • Fabrication of oxygen-doped hollow porous carbon nitride photocatalyst for ciprofloxacin degradation under visible-light irradiation

    Chitiphon Chuaicham, Keiko Sasaki

    ACS 2021 spring  

    発表年月: 2021年04月

  • シプロキサンを可視光分解するZnCr酸化物-フライアッシュ複合体の合成およびキャラクタリゼーション

    井上 拓海, Chitiphon Chuaicham, 笹木 圭子

    資源・素材学会春季大会2021  

    発表年月: 2021年03月

  • 黄銅鉱のバイオリーチングに対する共存炭素質物質の影響

    境 諒太郎, Kojo, T. Konadu, 笹木 圭子

    資源・素材学会九州支部春季例会2020  

    発表年月: 2020年05月

  • Biological pretreatment of carbonaceous matter in double refractory gold ores: a review and some future considerations

    Kojo T. Konadu, Diego M, M. Flores, Robert J. Huddy, Susan T. L. Harrison, Takashi Kaneta, Keiko Sasaki

    IBS 2019  

    発表年月: 2019年10月

  • Effect of carbonaceous matter on bioleaching of Cu from chalcopyrite ore

    Kojo T. Konadu, Ryotaro Sakai, Diego M.Mendoza, Chitiphon Chuaicham, Hajime Miki, Keiko Sasaki

    IBS 2019  

    発表年月: 2019年10月

▼全件表示

共同研究・競争的資金等の研究課題

  • 海水浮遊選別による難処理複雑硫化銅鉱からの革新的Cu-As-Mo分離法の開発

    日本学術振興会  科学研究費助成事業 基盤研究(A)

    研究期間:

    2022年04月
    -
    2026年03月
     

    三木 一, 笹木 圭子, Suyantara Gde・Pandhe・Wisnu

  • 光とジオミメティクスを活用したグリーンマテリアルの創成

    日本学術振興会  科学研究費助成事業 基盤研究(A)

    研究期間:

    2022年04月
    -
    2025年03月
     

    笹木 圭子, 赤松 寛文, 齊藤 敬高, CHUAICHAM CHITIPHON

  • 不純物として鉄を含む粘土鉱物を空間制御反応場とする可視光応答型光触媒複合体

    日本学術振興会  科学研究費助成事業 挑戦的研究(萌芽)

    研究期間:

    2022年06月
    -
    2024年03月
     

    笹木 圭子

  • カーボンネガティブを実現する窒化炭素と鉄鋼スラグの光触媒複合体の合成

    日本学術振興会  科学研究費助成事業 特別研究員奨励費

    研究期間:

    2022年04月
    -
    2024年03月
     

    笹木 圭子, SRIKHAOW ASSADAWOOT

  • CO2削減のための光触媒複合体の化学設計およびDFT解析

    日本学術振興会  科学研究費助成事業 特別研究員奨励費

    研究期間:

    2021年11月
    -
    2024年03月
     

    笹木 圭子, SHENOY SULAKSHANA

     概要を見る

    The present study focuses on development of g-C3N4/multi-metal oxide semiconductors for photocatalysis applications (mainly CO2 reduction). Towards this end, g-C3N4 was synthesized in a polycondensation process (550oC, 2h) by employing urea as a precursor. CaFe2O4 is chosen among a large number of mixed metal oxides because of its strong visible light absorption efficiency (Eg ~ 1.9 eV) and compatible band edges with g-C3N4. Solution combustion synthesis approach was used to prepare CaFe2O4. In-situ reaction process was used to synthesize g-C3N4/CaFe2O4 composites. XRD confirmed the existence of both crystal phases in the synthesized photocatalysts without any impurity peaks. The bands of g-C3N4 (-NH2 stretching), (C-N and C=N) and triazine rings were intact after the addition of CaFe2O4 as confirmed from FTIR. Porous nanosheets of g-C3N4 are grown over CaFe2O4 particles as observed by SEM. The bandgap of g-C3N4 reduced from 2.65 to 2.45 eV after the addition of CaFe2O4. Complete photodegradation (100%) of ciprofloxacin and phenol was achieved within 30 and 120 min of light irradiation. The lower intensity PL peaks and smaller sized semicircle in the EIS plots confirmed the effective separation and transfer of charge carriers in g-C3N4/CaFe2O4. The valence band edges of g-C3N4 and CaFe2O4 obtained from XPS were 1.57 and 2.10 eV. The calculated conduction band edges from UV-DRS were -1.08 and 0.2 eV for g-C3N4 and CaFe2O4 respectively. The involvement of O2- radicals as main species in the degradation confirms that g-C3N4/CaFe2O4 forms direct Z-scheme heterostructure.

  • 超難処理金鉱石を拓く新規バイオテクノロジーの創出

    日本学術振興会  二国間共同研究(オープンパーtナーシップ)

    研究期間:

    2021年04月
    -
    2023年03月
     

  • 超難処理金鉱石のバイオハイドロメタラジー研究拠点の形成

    日本学術振興会  研究拠点形成事業

    研究期間:

    2020年04月
    -
    2023年03月
     

  • グラファイト質金鉱石のバイオハイドロメタラジーの学理

    日本学術振興会  国際共同研究強化(B)

    研究期間:

    2019年10月
    -
    2023年03月
     

    笹木 圭子

     概要を見る

    リグニン分解性酵素による超難処理金鉱石中のグラファイト質の分解過程において生ずる分解中間産物が鉱物粒子の造粒化を起こすことがわかっている。この造粒化が金の回収率を高める妨げになっている可能性があり、これを回避する方策として、架橋剤として働いている可能性の最も高い第二鉄イオン(Fe3+)をプロセスから除去し、金回収率が向上することが明らかとなった。
    また、金(Au)と銀(Ag)を同時に含むグラファイト質金鉱石では、それぞれの存在様式が異なるために、Auの抽出には酵素処理を施さなくてもほぼ100%の回収率を示したものの、Agの抽出率は酵素処理前では30%台にとどまっていたところが、酵素処理を追加した逐次バイオ法ではほぼ100%に達した。
    酵素反応後の固体残渣のキャラクタリゼーションとして、豪州カーティン大学におけるQEMSCAN解析は先方の責任者の異動により、予定通り進まなかったが、その代わりに、グラファイト質のモデルである活性炭を基質とした酵素処理の固体残渣抽出物をGCMS分析によって酵素処理後の固体残渣の特性化をはかった。その結果、単環あるいは複環芳香族炭化水素を経由して脂肪族炭化水素が表面残留中間体として生ずる反応ルートが推定された。官能基の乏しい脂肪族炭化水素にまで分解されれば、酵素処理後の微粒子の造粒化による金の埋没から回収ロスという流れを回避できるものと考えられる。また、酵素活性は60℃程度の高温域が最大となるものの、この温度では一方で分解産物の多量体化も進み、金粒子の埋没など負の要素が出てくることも明らかとなった。

  • 農薬および薬剤廃液を分解する粘土鉱物を支持体とした金属フリー光触媒の開発

    日本学術振興会  特別研究員奨励費

    研究期間:

    2019年11月
    -
    2022年10月
     

    笹木 圭子

     概要を見る

    Hollow porous g-C3N4 were successfully synthesized and characterized by XRD, FT-IR, BET, XPS, Pl, Impedance, Photocurrent, SEM, TEM and mapping analysis. The as-prepared metal-free nanocomposite shows an outstanding photocatalytic activity for the detoxification of ciprofloxacin under visible light irradiation. (Communicated to Chemical communications)
    The porous g-C3N4 composite with polypyrrole and montmorillonite clay were synthesized and utilized for the degradation of metronidazole under visible light. The degradation pathways were confirmed by LC-MS analysis. (Submitted to Environmental Science Nano)
    The GQDs decorated porous graphitic carbon nitride with polyaniline nanocomposite were prepared and used for the photocatalytic degradation of various toxic pollutants including ciprofloxacin, imidacloprid, tetracycline, phenol, and rhodamine B under similar conditions. (To be submitted to Applied Catalysis B Environmental)

  • 産業廃棄物を基としたセメント系材料による有害重金属の不溶化および固化技術の開発

    日本学術振興会  科学研究費助成事業

    研究期間:

    2019年07月
    -
    2022年03月
     

    笹木 圭子, ZHOU CHUNCAI

  • 海水を利用した浮遊選別法によるヒ素含有難処理硫化銅鉱からの銅・モリブデン分離回収

    日本学術振興会  科学研究費助成事業 基盤研究(B)

    研究期間:

    2019年04月
    -
    2022年03月
     

    三木 一, 笹木 圭子

     概要を見る

    一昨年度までの研究により、難しいとされてきた含ヒ素銅精鉱からの浮遊選別によるヒ素の分離を、安全で安価な過酸化水素水を添加することにより分離できることを明らかにしてきた。また、含モリブデン銅精鉱からのモリブデンと銅の分離についても、従来使用されてきたNaHSと比較して安全で安価なピロ亜硫酸ナトリウム(MBS)の添加により、また特に海水を用いて行うことが出来ることを報告してきた。
    昨年度においては、より実操業に近い方法による検討を行うため、採掘を行った鉱石からの処理方法について検討を行った。実際の選鉱場でのプロセスを参考に、鉱石の粉砕、ふるい分け、粗選の最適な条件を見出し、その結果得られる実精鉱試料を用いて、含ヒ素銅精鉱からのヒ素分離、含モリブデン銅精鉱からのモリブデン分離について検討したところ、鉱石および精鉱を用いても、同様に浮遊選別による分離を行うことが出来ることが明らかになった。分離効率は約60-70%と高く、様々な不純物が含まれている系においても処理条件、攪拌条件の調整により処理が可能であった。
    また、銅とヒ素の分離に使用する過酸化水素水、銅とモリブデンの分離に使用するピロ亜硫酸ナトリウムの効果について、表面分析をXPSで行うことにより検討した。その結果、過酸化水素やMBS処理により、硫ヒ銅鉱等の含ヒ素銅鉱物、輝水鉛鉱などのモリブデン鉱物は、表面性状の変化が少なく疎水性であったが、主要な銅鉱物である黄銅鉱や斑銅鉱の表面はFeOOH等の親水性生成物が存在しているために、親水性となり、これらのために浮遊選別において分離が可能であることが分かった。不純物の効果を見るために、一般に銅鉱石中に含まれる銅藍、輝銅鉱を、銅線と硫黄から焼成することにより作成し、浮選による検討も行っている。これらの結果は、各種学会、論文において発表し、高い評価を得ている。

  • 炭素質頁岩含有鉱石からの金属資源回収のためのバイオテクノロジー

    日本学術振興会  二国間共同研究

    研究期間:

    2019年04月
    -
    2022年03月
     

  • 産業廃棄物を基としたセメント系材料による有害重金属の不溶化および固化技術の開発

    日本学術振興会  特別研究員奨励費

    研究期間:

    2020年03月
    -
    2022年02月
     

    笹木 圭子

  • グラフェンナノメッシュを用いたリチウムイオンキャパシタの新規負極材料の開発

    日本学術振興会  科学研究費助成事業 特別研究員奨励費

    研究期間:

    2018年11月
    -
    2021年03月
     

    笹木 圭子, SAWANT SANDESH

  • ジオミメティクスを活用した放射性核種の長期安定化への技術革新

    日本学術振興会  基盤研究(A)

    研究期間:

    2019年04月
    -
    2021年03月
     

    笹木 圭子

     概要を見る

    セメント固化体中で形成される層状複水酸化物(LDH)は放射性オキソ陰イオン核種のマトリクスとなる。核種を取り込んだLDHの安定性に対する土壌圏のアミノの影響を予測し、実験と理論計算により、とくに移動性の高いセレン酸を陰イオンモデルとして検討した。
    異なるアミノ酸5種を検討したところ、セレン酸の不安定化への影響はアミノ酸の種類に依存していた。MgAl-LDHはCaAl-LDHに比べてかなり安定であるが、総じて芳香族性を持つTrp, Pheはインターカレーションが起こりにくく殆ど影響を与えなかった。一方、芳香族性がなく小分子のGly, Asp, Cysはイオン交換を伴いセレン酸の溶出を促進した。MgAl-LDHの場合では、定常状態に至った固体残渣のXRD解析から得られたLDHの層間距離は、DFT計算から予測されたセレン酸およびイオン化されたアミノ酸単分子がLDHの金属層に配位したものと比較的よい一致を示し、アミノ酸とMgAl-LDHの金属層の間の相互作用は水素結合であると推定された。
    これに対して、CaAl-LDHの場合では、定常状態に至った固体残渣のXRD解析から得られた層間距離は複雑で、残留セレン酸の水和状態の異なるものが複数見られ、イオン化されたアミノ酸に加え、炭酸イオンの影響も重なっていた。DFT計算により収束した構造モデルによれば、アミノ酸とCaAl-LDHの金属層の間の相互作用は水素結合のほかにCa-O化学結合の形成が関わっていた。イオン化されたアミノ酸のカルボキシル基は、価数の大きいAlではなく、原子サイズの大きいCaと結合しやすいことが初めて理論的に説明された。CysはAspやGlyとは異なり、炭酸イオンを介在させにくく、セレン酸をより安定にLDHの層間に留める特徴を示した。
    以上の結果は、移動性の高い負電荷低レベル放射性核種の長期安定性に対し有用な知見を与える。

  • 薬剤廃液処理のための可視光誘導型光分解触媒の開発

    日本学術振興会  特別研究員奨励費

    研究期間:

    2018年11月
    -
    2020年10月
     

    笹木 圭子

     概要を見る

    本研究では、p型半導体であるCu2Oの光触媒としての合成法について、形態制御、サイズ制御、副産物であるCuO, Cuとの複合化・成層様式、n型半導体との複合化などのさまざまなバリエーションを、構造的特性化および光学的特性化をしたうえで、フェノール系の薬剤物質の分解効率によって評価・検討したものである。
    Cu2Oは低コストのp型半導体で、電子が存在することのできない価電子帯と伝導体のバンドギャップ(禁制帯)が2.17 eVであることから、可視光のエネルギーで電子励起が可能な可視光触媒となる。しかしながら、このバンドギャップの範囲でCu2Oは酸化還元反応を受けやすく、光学的安定性が乏しく、光化学反応のもととのある励起電子が容易に価電子帯に戻るという再結合を起こしやすい。これを克服すべく、これまでさまざまなCu2Oの構造上の改変の試みがなされてきたが、n型半導体であるTiO2との複合化がCu2Oの光酸化腐食を防ぎ、還元型酸化グラフェンとの複合化が比表面積の増大、バンドギャップの調節、励起電子の移動性の改善に効果的であることなどが明らかにされていた。
    これらを背景として、本研究は、ナノスケールでCu2Oの形態制御、比較的資源量の豊富なTiO2との複合化法の改善、2次元材料であるグラフェンとの統合法の改善により、新規光触媒複合体の合成法を明らかにし、これを低濃度のフェノール系薬剤廃液の光触媒反応による分解無毒化に応用した。
    本研究の成果は、3報の論文として公表し、さらに2編の論文を投稿中である。また、Materials Todayにbook chapter を発表し、Cu2Oの形態制御、サイズ制御、異種伝導体との接合様式の重要性を強調している。

  • 光触媒機能を付与した環境修復材の応用に向けた金属有機構造体・粘土鉱物複合体の合成

    日本学術振興会  科学研究費助成事業 特別研究員奨励費

    研究期間:

    2017年11月
    -
    2020年03月
     

    笹木 圭子, PAWAR RADHESHYAM

     概要を見る

    有機金属構造体(MOF)は、中心金属とリンカーの組み合わせによって、高分子のような連続構造をとり、比表面積が高く、安定なだけではなく、中心金属やリンカーの特性により、さまざまな機能を付与でき、吸着材や触媒など機能性化学物質として、近年最も注目されている。なかでもガスフィルターとしての用途が最も実用化に近いといわれ、とくにCO2吸着剤としての開発研究が盛んである。しかし、本研究では、あまり研究例のない水溶液溶媒でのMOFの活用、とくに有害水溶性物質の光分解、光触媒機能による還元、陰イオンの吸着除去を目指して、水溶液中でのMOF合成法を開発および最適化し、合成したMOFの特性化、応用までを行った。ソルボサーマル法に代わる水溶媒での合成法の開発では、超音波法、マイクロ波法を試み、モジュレーターおよびリンカーの選択、モジュレーター量、、周波数、官能基の導入など300を超える実験条件をこなし、アプリケーションにおける反応効率の向上をめざした。さらに、MOFと粘土鉱物により複合体を合成し、可視光域で水溶液中での色素物質の分解、Cr(VI)の還元に機能する光触媒効率を評価した。
    本申請課題の中心であるMOF/粘土鉱物複合体による色素分子ローダミンBの光触媒分解では、MOFとしてZr6O4(OH)4(ABDC)6 (ABDC = 2-aminobenzene-1,4-dicarboxylic acid)を合成し、粘土として針状結晶のセピオライトを選び、複合材料の最適混合比を認めた。合成MOFは2.83 eV のバンドギャップをもつ可視光触媒で、光励起電子はセピオライトの導電帯に移り、スーパーオキシドラジカルを生成し、色素分子を酸化分解する機構を提唱した。このように、粘土鉱物は単なる支持体ではなく、光触媒反応の電子輸送にかかわっていることを示した。
    成果は国際学術誌4編にまとめられた。

  • 炭素質頁岩の酵素分解を組み込んだゴールドバイオミネラルプロセッシングへの挑戦

    日本学術振興会  挑戦的研究(萌芽)

    研究期間:

    2018年06月
    -
    2020年03月
     

    笹木 圭子

     概要を見る

    炭素質頁岩を含む金鉱石は、金含有量が高いにもかかわらず、金回収率が低い。この理由は炭素質物質がシアン金錯体を吸着して、回収率を下げてしまうためで、効率の点、環境保全の点の両面から満足すべき解決法が確立されていない。本研究では、高温高圧条件を用いることなく、バイオテクノロジーによる炭素質物質の酵素分解を組み込んだ金回収法の確立を目指した。鉄酸化菌による硫化物の分解、続いて白色腐朽菌の放出粗酵素液による炭素質物質の分解を組み合わせることによって、シアン抽出による金回収率は、未処理段階で24%であったものが、92%にまで向上した。リグニン分解性酵素が炭素質物質の分解に寄与しているものと考えられる。

  • ナノ粒子Pdの形成場としての自己組織化イオン液体修飾酸化グラフェン複合体の合成

    日本学術振興会  科学研究費助成事業 特別研究員奨励費

    研究期間:

    2017年04月
    -
    2019年03月
     

    笹木 圭子, KANCHARLA SRINIVASARAO

     概要を見る

    The platinum group metal (PGM) reserves are depleting severely every year, and the demand to supply ratio is forecast to widen significantly by 2020. These factors induce the growing pressure on PGM recycling. High-level liquid waste (a spent nuclear fuel), spent automotive catalyst leachates are potential secondary sources for the urban mining of PGMs. The preparation of high acid tolerant and efficient functional materials is a challenging task in the solid phase recovery of noble metals. To overcome this issue, covalently functionalized graphene oxide (GO) materials were explored. The GO was covalently functionalized with 1-(3-aminopropyl)imidazole (ImGO), 2-methylthiophene (ThpGO), 2-aminoethanethiol (CysGO) through amide or amine formation at different reactive sites. Both ImGO and ThpGO were found efficient for the selective extraction of Pd from HLLW containing several metal ions. Both the materials could be recycled without a drop in efficiency for the studied five cycles.
    CysGO was employed for the recovery of precious metals from the simulated spent catalyst leachates containing various PGMs (Pd, Pt and Rh), rare metals (Zr, Y, La and Ce), alkaline earth metals (Ba), and base metals (Cu, Fe, Zn, and Ni) at 1M acid concentration. CysGO could selectively extract precious metals from all three medium with Pd (87.7 mol%) as major component and Pt co-adsorbed in small amount. The regenerated materials were converted into PGM nanoparticle supported graphene materials, a well-known heterogeneous catalyst through simple pyrolysis under N2 atmosphere at 500oC.

  • ヒ素およびフッ素除去のための機能性吸着剤の化学設計

    日本学術振興会  科学研究費助成事業 特別研究員奨励費

    研究期間:

    2016年10月
    -
    2019年03月
     

    笹木 圭子, SUBBAIAH MUTHU PRABHU

     概要を見る

    It was aimed to synthesize a modulator (benzoic acid (BA))-driven zirconium-fumaric acid (Zr-fum) metal-organic frameworks (MOF) and investigated in detail the adsorption mechanism of arsenic oxyanions (AsO43- and AsO33-) and their stability before and after the adsorption from water. The mechanism of AsO43- and AsO33- interaction on Zr-MOF was ligand-exchange and found to be the maximum uptake performance of AsO43- (1.159 mmol/g) and AsO33- (1.121 mmol/g) was obtained by the Langmuir adsorption isotherm. Likewise, it is also synthesized La-based MOFs with the linkers of benzoic acid (BA), 1,4-benzene dicarboxylic acid (BDC) and 1,3,5-benzenetricarboxylic acid (BTC). Interestingly, the ligand of BA approached La metal to form lanthanum methanoate (La(HCOO)3 instead of La-BA MOF through acid catalyst amide-hydrolysis mechanism, where, La-BDC and La-BTC as MOFs, confirmed by PXRD patterns. This is the first report to investigate the AsO43- adsorption and their dissolution behavior over La-BA, La-BDC and La-BTC in detail using the different spectroscopic methods. The maximum adsorption capacities of AsO43- obtained from the Langmuir isotherm model were found to be 2.623 mmol/g, 3.891 mmol/g and 0.280 mmol/g for La-BA, La-BDC and La-BTC, respectively. The value for La-BDC was recorded as one of the much superior, next to UiO-66, to the previously reported adsorbents for AsO43- till date. In addition, the zirconia nanoparticles (ZrO2) embedded graphene oxide dendrimer was prepared and utilized for removal of toxic AsO33- removal from water.

  • 放射性核種埋設に向けたジオミメティクスに由来する新規吸着材の開発

    日本学術振興会  基盤研究(A)

    研究期間:

    2016年04月
    -
    2019年03月
     

    笹木 圭子

     概要を見る

    半減期が長く、拡散しやすい性質を持つ陰イオン性核種の吸着剤あるいは不溶化法の開発を行った。セレン酸および亜セレン酸に対しては、ハイドロカルマイトやエトリンガイトとの共沈、あるいはこれらをイオン交換体とする吸着によって除去されやすかった。ヨウ素酸の不溶化は、エトリンガイトやハイドロキシアパタイトとの共沈が有効であり、ハイドロカルマイトにはあまり不溶化されない。一方、ヨウ化物イオンは、これらのいずれにも不溶化されず、第4級アンモニウムイオンを有する界面活性剤による修飾粘土が唯一有効な吸着体であった。この傾向は、過テクネチクム酸の代替イオンである過レニウム酸も同様であった。

  • 環境材料として機能化した層状複水酸化物ナノシートの設計

    日本学術振興会  科学研究費助成事業

    研究期間:

    2015年11月
    -
    2018年03月
     

    笹木 圭子, PAULMANICKAM KOILRAJ

     概要を見る

    水環境での有害な陰イオンを除去する目的で、保持時間が長く効率よく機能するイオン交換体の合成を目指し、ナノシート型層状複水酸化物の合成方法(ディラミネーション)、キャラクタリゼーション、性能評価、およびナノシートという特性を生かした機能付与をおこなった。
    1)Mg-Al型および Zn-Al型層状複水酸化物ナノシートをボトムアップ法で行い、合成したMg-Al型および Zn-Al型層状複水酸化物ナノシートをAFM, PXRD, FT-IR, TEM, Uv-Vis, 27Al-NMRにより特性化した。層状複水酸化物ナノシートの生成機構に関する情報としてEXAFS測定を行い、解析した。2)Mg-Al型層状複水酸化物ナノシートでは、アルギン酸ビーズ化により集積体とし、カラム式連続試験によってヒ酸イオンの吸着除去試験をおこない、集積体としてハンドリング性を向上させるとともに、ヒ酸除去効果も維持されることを実証した。3)アミノ酸アンカーとした層状複水酸化物ナノシートの用途として、重金属イオンの除去をおこなった。吸着容量、選択性、pHの影響などを検討した。重金属イオン除去のメカニズムをさまざまな分析方法を総合して検討した。4)層状複水酸化物ナノシートを用いて、電荷が1価で静電的に吸着しにくいハロゲンイオンおよびオキソハロゲンイオンの吸着効率を調べた。5)ナノシート型層状複水酸化物によるクロム酸イオンの吸着、それに続く還元、析出の機構をとりこみ機構を EXAFS や XPSによりおこなった。

  • 高ヒ素含有銅鉱石ミネラルプロセシングのイノベーション

    日本学術振興会  科学研究費助成事業 基盤研究(A)

    研究期間:

    2015年04月
    -
    2018年03月
     

    平島 剛, 笹木 圭子, 沖部 奈緒子, 三木 一

     概要を見る

    鉱物表面の酸化を利用して浮選で銅鉱石と高ヒ素含有銅鉱石、輝水鉛鉱等を分離回収可能であることを明らかにした。また、浮選分離が困難な高ヒ素含有銅鉱石(主に黄銅鉱と含ヒ素硫化鉱物)については、新規に見出した加熱処理・磁力選別法により分離が可能であることを示した。加熱法としてはマイクロ波加熱も有効であった。さらに、高ヒ素含有銅鉱物をバイオ・ケミカルリーチングによりCu回収し、Asをスコロダイト化する機構を明らかにした。石炭改質液を利用した酸性鉱山廃水抑制のための硫化鉱物の安価なマイクロカプセレーション化処理法を提案し効果的であることを示した。これらの結果から最適処理フローを示した。

  • 脂質支持膜への細胞融合法の開発と膜タンパク質計測への応用

    日本学術振興会  科学研究費助成事業

    研究期間:

    2014年04月
    -
    2017年03月
     

    金田 隆, 笹木 圭子, 武安 伸幸, 東谷 直樹, 金地 啓介, 小林 桜子, 牧 朋美, 尾川 冬馬, 苅田 真吾, 光延 愛美, 島田 雄飛, 原田 愛梨, 工藤 すみれ, 礒山 美華, 久保井 麻衣, 藤井 達也, 三木 笙子

     概要を見る

    本研究は、細胞膜に局在する膜タンパク質を計測するための新しいサンプリング法として、基板上に作製した脂質二分子膜に生体細胞を融合させる技術を確立し、その手法を活用した細胞膜の膜タンパク質分離、並びに計測方法を開発することを目的とした。基板上に細胞膜を展開し、それを観測するための全反射蛍光観察システムを作製し、それを用いた脂質固定化膜形成の観察、平面化した細胞膜の観察を行い、細胞膜に局在する膜タンパク質の計測法開発を行った。

  • バイオテンプレートによるリチウムイオンシーブの合成と集積化

    日本学術振興会  挑戦的研究(萌芽)

    研究期間:

    2015年04月
    -
    2017年03月
     

    笹木 圭子

     概要を見る

    化学反応では不可能な中性領域においてMn(II)を酸化する真菌によるバイオミネラリゼーションから合成したマンガン酸化物の焼成条件を最適化することによって、戦略元素の一つであるリチウムイオンの吸着体の合成に成功した(最大吸着容量24.7 mg/g-吸着体)。この吸着体は粉末状であるため、ハンドリング性を向上させるために、高分子ゲル埋包型として集積化した。集積体のリチウムイオン吸着速度は、粉末状のものと比べて遅くなったが、最大吸着容量および再生性は粉末のものと同等であり、高分子ゲル埋包型集積化は、リチウムイオンの吸脱着を反復することを前提とした分離性に大きく貢献した。

  • ジオミメティクスによる環境材料の創成

    内閣府  最先端・次世代研究開発プログラム

    研究期間:

    2010年02月
    -
    2014年03月
     

    笹木圭子

  • ナノジオサイエンスに基づく環境材料の探索と創出

    日本学術振興会  科学研究費補助金 基盤研究(A)

    研究期間:

    2010年04月
    -
    2013年03月
     

    笹木圭子

  • ヒ素耐性Biomining微生物の創製およびその資源工学的評価

    日本学術振興会  科学研究費助成事業

    研究期間:

    2011年04月
    -
    2012年03月
     

    笹木 圭子

  • 未利用炭素資源活用によるバイオコールエコ燃料製造システムの開発

    日本学術振興会  科学研究費助成事業

    研究期間:

    2009年
    -
    2011年
     

    平島 剛, 野中 壯泰, 笹木 圭子

     概要を見る

    現在のところ有効利用されていない低品位炭と廃バイオマスに関して、水熱処理と物理選別を主要技術とした包括的な有効利用法について検討した。その結果、バイオコールエコ燃料製造のみならず、改質液、ガス産物の有効利用と温室効果ガス削減の可能性について、また、燃焼後のフライアッシュ中に存在する高強度中空球形セラミックスの製造、回収方法について有用な知見を得た。

  • 鉄酸化細菌ヒ素耐性株によるバイオミネラルプロセッシングのイノベーション

    日本学術振興会  科学研究費補助金 挑戦的萌芽研究

    研究期間:

    2008年04月
    -
    2010年03月
     

    笹木圭子

  • 微生物機能により合成されたマンガン酸化物に対するレアアース元素の選択吸着

    日本学術振興会  科学研究費助成事業

    研究期間:

    2009年
    -
    2010年
     

    平島 剛, 笹木 圭子

     概要を見る

    申請者らが単離したマンガン酸化真菌Paraconiothyrium sp.WL-2 strainにより合成されたマンガン生体鉱物それ自身は、低結晶性層状バーネサイトに近い。自然界ではこの生物酸化の過程で、種々の重金属やレアアースを取り込み、バーネサイトに対する単純な吸着ではなく、共沈や共吸着に近い現象が起きている。それにより、単純な吸着以上の重金属取り込み量が得られており、微生物が合成した低結晶性層状バーネサイト中の空隙のサイト数が多く、Mn(III)含有率が低いほど、重金属やレアアースの取り込み量が大きくなることをEXAFS解析より明らかにした。また微生物機能に由来した低結晶性層状バーネサイトを焼成したものからLiイオンシーブを合成することができ、同一合成条件では、微生物機能に由来した低結晶性層状バーネサイトは、化学的に合成されたその他種々のマンガン酸化鉱物と比較しても、効率の高いリチウムイオンシーブを合成する出発物質であることがわかった。これらについては地球化学分野では世界最大規模の国際学会Goldschmidt 2011 (Prague,Czech Republic)にて成果発表を予定している。自然界におけるマンガン堆積環境には原生動物が多数みられ、マンガンを酸化する真菌や細菌との捕食関係が推定される。微生物機能により合成された比較的低結晶性のマンガン酸化物であっても、その結晶性の高い部分にレアアースなどの稀元素は比較的高い含有量を示した。これは、酸化の過程で規則的に取り込む機構が起きていることを示唆している。これらについては、the 25^th International Applied Geochemistry Symposium (Rovaniemi,Finland)にて成果発表を予定している。

  • 微生物処理による地下水浄化のための透過型浄化壁におけるヒ素の輸送モデル

    日本学術振興会  科学研究費助成事業

    研究期間:

    2009年
    -
    2010年
     

    OSAMA Eljamal, 笹木 圭子, OSAMA Eljamal Mm

     概要を見る

    本研究の目的は,室内実験や数理モデルによる数値シミュレーションを通して,ヒ素除去技術を開発することにある.その際,数理モデルは,ゼロ価鉄を透過型浄化壁として使用することで水からヒ素を不動化するメカニズムや,その主要要因を解明するためのツールとして利用される.
    本研究の2年目となる今年度は,ゼロ価鉄を使用して水からヒ素を除去する際のメカニズムの詳細に関連して,バッチテストを中心に検討を行い,吸着反応速度の定量化とそのモデル化を行った.
    まず,五酸化ニヒ素や三酸化二ヒ素の吸着反応速度に対するヒ素濃度の影響を検討した.その結果,五酸化ニヒ素はゼロ価鉄の表面吸着で除去され,一方,三酸化二ヒ素はゼロ価鉄により吸着されるとともに,五酸化ニヒ素に酸化されることを示すとともに,異なる濃度における一次反応モデルの反応速度を定量化した.
    さらに,これらのバッチ試験の結果や推定したヒ素除去メカニズムを基本に,化学反応の概念モデルを構築し,バッチ試験結果に適用するとともに,溶質輸送モデルとカップリングしてカラム試験結果にも適用した.シミュレーションの結果,ヒ素不動化はゼロ価鉄に強く影響を受けること,五酸化ニヒ素はゼロ価鉄の表面吸着で除去され,一方,三酸化二ヒ素はゼロ価鉄により吸着されるとともに,五酸化ニヒ素に酸化されること,五酸化ニヒ素の吸着速度パラメータは三酸化二ヒ素のそれより大きく,三価鉄の影響を受けること,などが明らかになった.また,開発したモデルは,ゼロ価鉄を透過型浄化壁として使用することによるヒ素除去法の能力予測に使用可能であることも示された.

  • 低酸素環境におけるマンガンのバイオミネラリゼーション

    日本学術振興会  科学研究費補助金 挑戦的萌芽研究

    研究期間:

    2006年04月
    -
    2008年03月
     

    笹木圭子

  • 透過型浄化壁における微生物群集構造の長期モニタリング

    日本学術振興会  科学研究費助成事業

    研究期間:

    2007年
    -
    2008年
     

    平島 剛, 笹木 圭子, 土居 克実

     概要を見る

    前年度終了したカラム通水実験のカラム内容物の化学成分分析を蛍光X線分析法およびX線回折分析によりおこなった。蛍光X線分析結果からヒ素はカラム入り口から出口へと蓄積量が減少する傾向が顕著に見られ、X線回折分析からはゲータイト、レピドクロサイト、マグネタイト、フェリックアルセネイトの形成が見られ、Fe(III)系鉱物とヒ素が共沈している可能性およびFe(III)との沈殿形成が強く示唆された。カラム残渣の形態を走査電子顕微鏡により観察し、その一部をSEM-EDXにより元素マッピングをおこなったところ、炭酸カルシウムの析出部分にヒ素の分布が重なっており、炭酸塩との共沈も明らかとなった。また一部の試料中のヒ素の化学状態をX線光電子分光法により測定し解析した結果、ヒ素はヒ酸および亜ヒ酸ともに鉄粉表面に検出され、吸着と酸化、共沈により不動化されたものと考えられる。ヒ酸を還元する微生物の寄与は固体分析からは明らかにはならなかった。硫酸還元菌により生じたはずである硫化物の存在はX線回折分析から明らかとはならず、結晶性が低かったためと思われる。このように前年度おこなったカラム試験では、固体残渣分析によれば、化学的な作用によるヒ素の不動化の証拠が強く表われて、微生物作用によるヒ素の不動化の証拠はそれに隠れ目立たない結果となった。しかし、溶液分析によれば、硫黄同位体効果やDGGE-PCR法による微生物群集構造解析から、確かに硫酸還元菌が寄与していたことが確かめられた。これらのことから、数十年持続させる透過型浄化壁に対して嫌気性微生物反応を主な浄化コンセプトとする場合、内容物に含める炭素源の選択、その供給量は、設計段階で予測しなければならない重要な要素となることが確認された。

  • アジア圏におけるバイオコールコプロダクションシステムの開発

    日本学術振興会  科学研究費助成事業

    研究期間:

    2006年
    -
    2008年
     

    平島 剛, 笹木 圭子, 野中 壯泰, 古山 隆, 林 信行, 福島 正巳

     概要を見る

    本研究では、アジア圏を対象とし、水分等が高いため未利用のバイオマスおよび低品位炭の混合水熱改質によるバイオマス・石炭混合燃料(バイオコール)製造とその製造あるいは燃焼過程において有機環境浄化剤、水素ガス、高強度中空セラミックスなどのコプロダクションシステムの開発を行うことを目的として研究をおこない、バイオコール、高濃度水素ガス、カテコール等の製造条件を明らかにするとともに、燃焼灰から高強度中空球形粒子を回収する方法を見出した。

  • 生体鉱物の特性を生かした地下水・土壌汚染修復技術の新展開

    日本学術振興会  科学研究費補助金 基盤研究(B)

    研究期間:

    2004年04月
    -
    2007年03月
     

    笹木 圭子

  • ヒ素汚染土壌のバイオレメディエーション

    日本学術振興会  科学研究費補助金 挑戦的萌芽研究

    研究期間:

    2004年04月
    -
    2006年03月
     

    笹木 圭子

  • バイオマスおよび未利用低品位炭を利用した環境負荷低減型スラリー燃料の開発

    日本学術振興会  科学研究費助成事業

    研究期間:

    2003年
    -
    2005年
     

    平島 剛, 恒川 昌美, 広吉 直樹, 笹木 圭子, 糸井 龍一, 野中 壯泰, 片桐 務, 古山 隆

     概要を見る

    流通式水熱処理装置を用いて、バイオマス・低品位炭単独及び混合改質における分解抽出挙動について検討した。その結果、両試料で異なる組成の有機物の抽出が確認され、混合改質ではバイオマスからの抽出物の一部を低品位炭が吸着することが分かった。また、改質液の吸光度とTOCは良い相関を示し、吸光度をモニタリングすることによってTOCの経時変化を予測出来ることがわかった。回分式及び連続式の水熱処理を行い、改質温度、混合比の燃料性に与える影響について検討した。その結果、低品位炭、バイオマス共に改質温度が高いほどより強く改質作用を受け、混合改質では両試料の反応は独立並行反応であると考えられた。また、混合比は無水基準の燃料特性に影響を与えるが、無水無灰基準では、炭素量、酸素量及び総発熱量に混合比による差異が無くなった。また、連続式水熱処理装置を用いた改質試験では5時間の連続運転に成功し回分式と遜色ない結果が得られた。水熱処理の際大量に発生する改質液について、キャラクタリゼーションを行った。その結果、いずれの改質温度の改質液にも酢酸、メタノールなどの酸、アルコール類の他に2,6-ジメトキシフェノール、グアヤコールなどの還元性の強いフェノール類が含まれており、一般に様々な分野で使用されている木酢液と似た成分から成ることが分かった。この改質液の環境浄化剤としての可能性について検討した結果、いずれの改質液もCr(VI)を有効に還元すること、またCr(VI)還元後の改質液に生石灰、消石灰を添加することによりCr(III)の大部分を溶液から沈殿物として除去できること、還元剤として硫酸第一鉄を使用した場合と比べてスラッジ量を1/2〜1/3倍に低減できることが確認された。

  • 鉱廃水の生物処理に対する炭素材料の応用

    日本学術振興会  科学研究費助成事業

    研究期間:

    2001年
    -
    2003年
     

    笹木 圭子, 金野 英隆

     概要を見る

    北海道南部駒の湯のマンガン堆積環境からマンガン酸化真菌を分離し、形態観察、生理学的性質、遺伝子解析からPhoma sp.と推定された。この菌は中性でMn(II)イオンを酸化し、もっとも酸化速度が速くなるのはpH6.8であった。有機炭素源の検討を行ったところ、グルコースは添加するとマンガン酸化速度が遅くなった。安定な酸化速度を維持するためにpeptoneとyeast extractは不可欠であることがわかった。また、有機炭素濃度を減らしたほうが高いマンガン酸化速度が得られた。またMn(II)濃度は最高120ppmまで酸化可能であることがわかり、これは実鉱山廃水中の濃度レベルに匹敵する。酸化が進行するにつれてpHが低下し、pH6.5以下になるとMn(II)の酸化は起こらなかったので、PIPESなどの適切な緩衝剤が必要である。PAN系炭素繊維を培養液の中に入れたときには、Mn(II)酸化速度が明らかに促進された。炭素繊維は真菌の着生体となり、増殖を安定化させ、マンガン酸化物は真菌の表面に付着して生成し、処理液が濁ることがなかった。ほぼ同じ形状のPET繊維ではこのような効果は表われなかったことから、炭素繊維のカビに対する生体親和性が寄与したものと推定される。また、炭素不織布ではこのような促進効果は認められなかった。生成したMn酸化物はX線回折によりγ-MnO_2(ramsdellite)であることが確認された。SEM観察によれば、スポンジ状の多孔質の表面をもち、細孔の平均径が4nmのメソポアで、炭素繊維を入れて合成した場合のほうが、細孔径サイズにばらつきが少ないことがわかった。この生体鉱物の形状および性状は、重金属イオンのスカベンジャー、酸化剤など、さらに第二の鉱廃水処理への応用とともに、スーパーキャパシターなどの電池材料への応用の可能性を持っている。

  • アーバンマイン構築のための資源処理・リサイクル技術と環境保全技術の開発

    日本学術振興会  科学研究費助成事業

    研究期間:

    2001年
    -
    2003年
     

    恒川 昌美, 平島 剛, 廣吉 直樹, 米田 哲朗, 吉田 豊, 笹木 圭子

     概要を見る

    日々,都市においては膨大な量の廃棄物が排出される。廃棄物中の有価物に着目し,これらの廃棄物を人工資源とみなし,その中の有価物を資源化・リサイクルする拠点としての都市域における新しいタイプの鉱山,いわゆるアーバンマインを創生・構築するための要素技術の開発研究を行った。得られた主な成果は以下のようである。
    1)廃コピー機の構成は,約50%が鉄,20-25%がプラスチックである。また,プラスチックの構成は,約48%がABS樹脂,約48%がポリオレフィン類(PS,PE,PP),残りがその他となっている。そこで研究代表者の研究室で開発したTACUBジグと磁選機を組み合わせてこれらの有価物を成分別に回収プロセスを開発した。
    2)都市ゴミの処理プロセスから発生する焼却飛灰,溶融飛灰中の有価金属を回収するため,種々の浸出-硫化法を検討し,新しい方法を見出した。
    3)ハイブリッド自動車に使用されている二次電池の正極材,負極材の物理選別法を開発し,湿式製錬技術と組み合わせることで,有価物の回収・リサイクルできるプロセスを見出した。
    4)廃コンクリートから再生骨材,モルタルを回収し,リサイクルするプロセスを開発した。
    5)微生物を用いた,含マンガン廃水の高度廃水処理法を開発した。
    6)マイクロエンキャプセレーションによる重金属汚染土壌の浄化法を新たに開発した。

  • 未利用低品位炭の改質によるエネルギー利用の効率化と環境負荷低減化

    日本学術振興会  科学研究費助成事業

    研究期間:

    2000年
    -
    2002年
     

    平島 剛, 笹木 圭子, 広吉 直樹, 恒川 昌美, 福嶋 正巳, 福嶋 正己

     概要を見る

    本研究では,HWD(Hot Water Drying,熱水乾燥)法による改質処理で脱水,疎水化し,これと物理的および化学的選炭とを組み合わせることで,ディーゼル発電燃料用のCWM(Coal Water Mixture)製造に適した低灰分炭(灰分5%以下)やウルトラクリーンコール(灰分1%以下)が得られることを見出した。また,HWD処理の際に生ずる溶液(改質液)中に有機還元物質が含まれていることに着目し,この改質液によるCr(VI)の還元について調べ,本液が汚染環境の浄化・修復の分野で利用できることを明らかにした。以下に、本研究の概要と主な成果について述べる。
    1.HWD法により改質時の温度を270,300,330℃と変えて改質を行い,改質に伴う低品位炭の諸性質の変化を調べた。いずれの石炭も,改質により水分,カルボキシル基起因酸素量,水酸基起因酸素量が減少し,発熱量が増加した。また,改質温度が高くなるほど,これらの効果は顕著になり,それに伴い表面疎水性が増大した。
    2.微粒の石炭に対する浮選では,改質炭のほうが原炭(未改質炭)より20〜30%高い可燃成分回収率を示し,精炭灰分も低くなった。これは,改質に伴い,石炭の表面疎水性が増すことによる。アルカリ熱水溶液法でBeluga炭の原炭および改質炭を処理した場合,改質炭のほうが,また改質炭でも改質温度が高いものほど可燃成分回収率は高く,精炭灰分は低くなった。改質炭についてはいずれの条件下でアルカリ熱水溶液処理しても精炭の灰分が5%以下となり,さらに改質炭を3回浮選して得た精炭について処理すると,灰分1%以下のウルトラクリーンコールが得られた。
    3.Beluga炭を種々の温度でHWD処理する際に得られる溶液(改質液)について,GC/MS, HPLC, GPCなどを用いてキャラクタリゼーションを行った。270℃改質液には酢酸と分子量1600〜3400程度のオリゴマーが共存しており,オリゴマーを構成している物質は脂肪族有機酸エステルであった。300℃改質液にはメタノールやカテコール,フェノールなどが,330℃改質液にはメタノール,アセトン,酢酸,フェノール,カテコールが含まれていた。改質温度が高くなるほど,改質液のTOC濃度も急激に増大し,またカテコール濃度も300℃改質液で10ppm,330℃改質液で1300ppmと増大した。これらの改質液に含まれるカテコール類が還元能を有することは,サイクリックボルタンメトリーによって確認した。
    4.いずれの改質液もCr(VI)還元能力を有しており,その還元能力は低pH領域でより強くなった。330℃および300℃改質液中にはその還元に有効に作用する物質としてカテコールが存在していることを示した。このような還元物質を含有している改質液は,今後,汚染環境の浄化・修復の分野での活用が期待できる。

  • バイオミネラリゼーションを活用した鉱廃水からのマンガン回収

    日本学術振興会  科学研究費助成事業

    研究期間:

    2000年
    -
    2001年
     

    笹木 圭子

     概要を見る

    道南部から道央部にかけての菱マンガン鉱をともなう鉱脈型鉱床に沿って、マンガン堆積環境を調査し、マンガン酸化活性が高いと思われる2種の細菌と1種の真菌を分離した。しかし、2種の細歯は実験室的に安定な増殖が困難であったので、1種の真菌と対照微生物として、ATCC標準株Leptothrix discophora(43182,51168)を用いて、マンガン酸化除去を試み、マンガン酸化によって得られた堆積物のキャラクタリゼーションをX線回折、蛍光X線、光電子X線分光法、走査電子顕微鏡観察によって行った。
    ATCC標準株Leptothrix discophora 51168はマンガン濃度24ppmまで酸化可能であることを確認し、しんとう培養よりも静置培養のほうが安定なマンガン酸化活性を保持することが分かった。一方、マンガン堆積環境から分離したマンガン酸化真菌は、ATCC標準株Leptothrix discophoraの培地では真菌自体は増殖して大きなコロニーを形成するが、Mn(II)イオンを酸化しなかった。しかし、有機炭素源を推奨培地の1/10にまで低減することによって、50ppmのMn(II)イオンを酸化し水溶液から除去することが可能でった。すなわち、分離されたマンガン酸化真菌は、有機炭素源を制限することによりMn(II)イオンを利用するようになった。この菌はPhoma sp.であることがわかった。
    Mn(II)イオン酸化によって得られた堆積物については、X線回折ではピークが得られないが、蛍光X線では明確なMnKαのピークが認められ、光電子X線分光法によりMn(III, IV)のの状態であることが明らかであった。真菌は水中に分散しやすい微細な粉末をまとめ回収に役立つこともわかった。

  • 廃蛍光管からの希土類元素の再資源化とその有効利用

    日本学術振興会  科学研究費助成事業

    研究期間:

    1999年
    -
    2001年
     

    平島 剛, 笹木 圭子, 広吉 直樹, 恒川 昌美, 長野 伸泰, 高橋 徹

     概要を見る

    本研究では、廃蛍光管からの希土類元素の再資源化とその有効利用に関して検討を行い、以下の結果を得た。
    1)廃蛍光管処理事業所から排出される廃蛍光体を試料とし、水力(湿式サイクロン)選別、風力(ターボプレックス)選別、薄流選別(Multi-Gravity Separator)、浮選により希土類蛍光体の選別試験を行なった。その結果、風力選別が最も高い分離効率を示したが、ニュートン効率は0.34と必ずしも満足できる選別成績ではなかった。
    2)理想的な分離が可能と考えられる遠心式重液選別試験を行った。しかし、親水性の廃蛍光体試料は、重液中に存在する微量水分により液架橋を形成し凝集を起こすため、選別成績は悪化するとともに再現性に乏しい結果となった。そこで廃蛍光体試料表面をNaOlで疎水化処理することで有機液体中での分散性を促進させ、さらに遠心力を加えることで回収率、品位を高める新しい選別方法を開発した。本研究で開発された方法により、ニュートン効率は0.81、全希土類蛍光体品位合計は38.7%、希土類蛍光体回収率は97.3%の高い選別成績が得られた。
    3)蛍光体スラッジ中のYおよびEuの最適硫酸浸出条件を明らかにするとともに、不純物は水酸化物沈殿法およびシュウ酸化合物沈殿法で除去できることを明らかにした。
    4)蛍光体スラッジからの希土類元素回収フローを構築するとともに、実用化回収実験を行った結果、純度98.2%、全工程での回収率65%の結果を得た。
    5)3),4)で回収した希土類元素を用いた希土類蛍光体合成フローを構築した。そのフローに従って合成した赤色蛍光体Y_2O_3:Eu^<3+>は平均粒径5〜6μmに揃った粒度特性および結晶子サイズ0.2μm以上の良好なY_2O_3:Eu^<3+>の結晶構造を有しており、市販蛍光体と同等な発光特性を有していることがわかった。

  • Biomineralization

  • Recycling of waste scallop shells

  • Bioremediation in mine environments

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Misc

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    三木 一, 沖部 奈緒子, SUYANTARA Gde Pandhe Wisnu, 小山 恵史, 笹木 圭子, 平島 剛, 中村 壮志, 青木 悠二, 田中 善之, 諏訪 貴大

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  • ヒ素含有一次硫化銅精鉱の活性炭バイオリーチングに関する研究

    林海人, 小山恵史, 忰山卓也, 青木悠二, 平島剛, 笹木圭子, 沖部奈緒子

    資源・素材学会春季大会(Web)   2021  2021年

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  • Biological pretreatment of carbonaceous matter in double refractory gold ores: A review and some future considerations

    Kojo T. Konadu, Diego M. Mendoza, Robert J. Huddy, Susan T. L. Harrison, Takashi Kaneta, Keiko Sasaki

    HYDROMETALLURGY   196  2020年09月

    書評論文,書評,文献紹介等  

     概要を見る

    The pretreatment of carbonaceous material in double refractory gold ores (DRGO) is necessary to decrease pregrobbing of gold and maximize gold recovery. DRGO contains of carbonaceous matter and gold grains encapsulated in sulfide minerals, which typically results in very poor gold recovery. However, there is growing interest in DRGO because some estimates show that it makes up about a third of the total available gold for production by mining. This can be achieved by chemical and biological techniques, however, the chemical techniques like flotation, surface passivation and chemical oxidation have received more extensive study and either have to be retooled or modified to be applied to the carbonaceous matter in the DRGO. In comparison, the biological techniques are relatively unknown with significant gaps in the knowledge about the bio-treatment mechanism, byproducts and avenues for scaling up like bioreactor design. This study reviews the enzymatic pretreatment of DRGO to facilitate gold recovery and minimize reagent consumption. It focuses on the potential for application of oxidative enzymes like lignin peroxidase, manganese peroxidase and laccase to pretreat carbonaceous matter in DRGO with or without an additional step of sulfide oxidation and addresses characterization of byproducts of the enzymatic decomposition. Further, potential bioreactor configurations for the enzymatic decomposition without direct contact of ore with microorganisms are considered, both in terms of understanding the mechanisms within the pretreatment and in terms of application.

    DOI

  • バイオハイドロメタラジーのすゝめ(第5回)23rd International Biohydrometallurgy Symposium(IBS2019)テクニカルツアー報告

    笹木 圭子, 沖部 奈緒子, 菅井 裕一, 三木 一, Santisak Kitjanukit, 工藤 淳子

    季刊資源と素材   5 ( 4 ) 48 - 52  2020年

    CiNii

  • バイオハイドロメタラジーのすゝめ(第4回)23rd International Biohydrometallurgy Symposium (IBS2019)開催報告

    笹木 圭子, 沖部 奈緒子, 菅井 裕一, 三木 一, 工藤 純子

    季刊資源と素材   5 ( 2 ) 53 - 56  2020年

    CiNii

  • 難処理性一次硫化銅鉱のバイオリーチングにおける活性炭添加の影響

    林海人, 小山恵史, 青木悠二, 黒岩樹人, 平島剛, 笹木圭子, 三木一, 沖部奈緒子

    資源・素材学会春季大会(Web)   2020  2020年

    J-GLOBAL

  • 難処理性一次硫化銅鉱のバイオリーチングにおける炭素触媒効果とその機構

    小山恵史, 高松恭平, 青木悠二, 黒岩樹人, 平島剛, 笹木圭子, 三木一, 沖部奈緒子

    資源・素材学会春季大会(Web)   2020  2020年

    J-GLOBAL

  • 黄銅鉱バイオリーチングにおける炭素材料触媒機構の解明

    高松恭平, 小山恵史, 三木一, 笹木圭子, 沖部奈緒子

    資源・素材学会春季大会(Web)   2019  2019年

    J-GLOBAL

  • 魚骨由来の水酸アパタイトを利用した浄化材料の開発

    後藤 知代, 笹木 圭子

    Journal of the Society of Inorganic Materials, Japan   25   297 - 303  2018年  [査読有り]  [招待有り]

    記事・総説・解説・論説等(学術雑誌)  

  • Optimization of microbiological redox potential control in chalcopyrite bioleaching

    Kyohei Takamatsu, Tsuyoshi Hirajima, Keiko Sasaki, Hajime Miki, Naoko Okibe

    14th International Symposium on East Asian Resources Recycling Technology, EARTH 2017    2017年  [査読有り]

     概要を見る

    © The Mining and Materials Processing Institute of Japan. Chalcopyrite (CuFeS2) is considered one of the most promising future copper resources, yet its relatively recalcitrant property to chemical and microbiological oxidation requires further technological improvement to enhance its dissolution. Our studies so far demonstrated utility of the “microbiological solution redox potential control” in chalcopyrite bioleaching to enhance chalcopyrite dissolution: Solution redox potentials were microbially controlled based on the Fe(III)/Fe(II) ratio by using “weak” to “strong” Fe-oxidizers to target different redox potential levels during the bioleaching. As a result, improved Cu recovery was achieved at 0 <Enormal <1, especially by utilizing the “weak” Fe-oxidizing bacterium, Sulfobacillus sp. strain YTF1 in mixed culture with Acidithiobacillus caldus strain KU (S-oxidizer) (Masaki et al., submitted). In order to optimize the process, this study further investigated the effect of various parameters (e.g., pH, initial Cu2+ concentration, and pulp density) on “microbially redox-controlled” chalcopyrite bioleaching reaction. Lowering the initial pHs (from 2.0 to 1.75, 1.5 and 1.25) lead to greater abiotic acid chalcopyrite dissolution, but a rapid pH increase in sterile controls (to 2.5-3.0) suppressed the final Cu recovery. Whilst in inoculated cultures, the greatest Cu recovery of 65% was obtained at pH 1.75 by day 70 (cf. 25% in sterile controls) by maintaining the Enormal level at around 0.43. Since the positive effect of starting at pH 1.75 (compared to pH 2.0) was likely attributed to the presence of acid-dissolved Cu2+ ions at the beginning of the bioleaching reaction, the next experiment intentionally added different concentrations of Cu2+ ions (0, 5, 10, 20 mM) before starting the bioleaching tests. The effect of Cu2+ addition will be presented and discussed at the conference.

  • As(III) oxidation and immobilization by activated carbon

    Yusuke Hotta, Tsuyoshi Hirajima, Keiko Sasaki, Naoko Okibe

    14th International Symposium on East Asian Resources Recycling Technology, EARTH 2017    2017年  [査読有り]

     概要を見る

    © The Mining and Materials Processing Institute of Japan. Production of acidic wastewaters containing highly toxic and soluble arsenite (As(III)) is a growing concern in copper refinery industries. This study aimed to investigate the utility of readily available activated carbon (AC) for oxidation and immobilization of As(III) from acidic wastewaters at a relatively moderate temperature (45°C). For comparison, effect of bio-AC (combination of AC with moderately thermophilic Fe(II)-oxidizing bacterium, Acidimicrobium ferrooxidans ICP) was also investigated. The initial AC pulp densities ranged between 1-25% for acidic solutions (pH 1.5) containing 1000 ppm of As(III) and Fe(II). When tested with an individual ion species (1000 ppm As(III) or Fe(II)) using 1% AC, it was confirmed that AC is capable of chemically catalyzing Fe(II) oxidation and As(III) oxidation. Following the oxidation, Fe(III) was found absorbed on the AC surface, while As(V) remained in the solution. When both ions were present, 78% As was immobilized (at day 14). By elevating the AC concentrations, As(III) oxidation was increasingly accelerated and 1000 ppm (III) was completely oxidized in 2 days (10, 25% AC). At 25% AC, 94% of As was removed as amorphous ferric arsenate within 2 days. Possible additional Fe(II) oxidation effect (thus facilitating further As(III) oxidation by coupling Fe(III) reduction-As(III) oxidation on the AC surface) was evaluated by preparing bio-AC. The expected effect was seen at low AC concentrations (0.5, 1%): At 1% bio-AC, oxidation of both Fe(II) and As(III) were accelerated compared to 1% AC. As a result, 57% As was immobilization at day 6 using bio-AC. In conclusions, higher AC concentrations lead to more effective As(III) oxidation and immobilization as amorphous ferric arsenate. This approach can be utilised as pre-treatment for final scorodite crystallization (at the same time recycling AC). Whilst use of bio-AC can be advantageous when treating dilute As(III) concentrations (<1000 ppm As(III)) using lower AC concentrations.

  • 銀触媒存在下における硫砒銅鉱バイオリーチングのメカニズム解明

    小山恵史, 平島剛, 笹木圭子, 三木一, 沖部奈緒子

    資源・素材学会春季大会(Web)   2017   ROMBUNNO.2201‐09‐09 (WEB ONLY)  2017年

    J-GLOBAL

  • 中温条件下における亜ヒ酸(As(III))の微生物学的酸化および不動化に関する研究

    惠良祐太, 平島剛, 笹木圭子, 沖部奈緒子

    資源・素材学会春季大会(Web)   2017   ROMBUNNO.3301‐10‐06 (WEB ONLY)  2017年

    J-GLOBAL

  • 低濃度亜ヒ酸含有製錬廃液からのバイオスコロダイト生成

    田中雅仁, 平島剛, 笹木圭子, 沖部奈緒子

    資源・素材学会春季大会(Web)   2017   ROMBUNNO.3301‐10‐05 (WEB ONLY)  2017年

    J-GLOBAL

  • 超好酸性鉄還元細菌を利用した貴金属バイオナノ粒子の生成および選択的回収

    松本昂大, 中山大輔, 平島剛, 笹木圭子, 沖部奈緒子

    資源・素材(Web)   2016   ROMBUNNO.PY‐44 (WEB ONLY)  2016年

    J-GLOBAL

  • 硫砒銅鉱のバイオリーチングにおける銀触媒の影響

    小山恵史, 平島剛, 笹木圭子, 三木一, 沖部奈緒子

    資源・素材学会春季大会(Web)   2016   ROMBUNNO.3606 (WEB ONLY)  2016年

    J-GLOBAL

  • 超好酸性鉄還元細菌を利用した貴金属バイオナノ粒子の生成

    松本昂大, 中山大輔, 平島剛, 笹木圭子, 沖部奈緒子

    資源・素材学会春季大会(Web)   2016   ROMBUNNO.1609 (WEB ONLY)  2016年

    J-GLOBAL

  • Removal of Boron by Co-precipitation with Hydroxyapatite Using Dolomite as a Starting Material

    Kenta Toshiyuki, Tomoyo Goto, Tsuyoshi Hirajima, Keiko Sasaki

    Proceedings of International Symposium Earth Science and Technology 2013     380 - 383  2013年12月

    記事・総説・解説・論説等(国際会議プロシーディングズ)  

  • 3S-Dp01 バイオマイニング研究の新展開(無機化合物の微生物変換研究の最前線,シンポジウム)

    沖部 奈緒子, 笹木 圭子

    日本生物工学会大会講演要旨集   65   181 - 181  2013年

    CiNii

  • Mg-Al系及びMg-Fe系複合酸化物を用いた水溶液中のB及びF^-の収着

    森山 紗好, 笹木 圭子, 平島 剛

    Journal of MMIJ : journal of the Mining and Materials Processing Institute of Japan   127 ( 12 ) 708 - 713  2011年11月

    CiNii

  • フィンランドの鉱区活用および休廃止鉱区環境対策 : IAGS2011エクスカーションに参加して

    笹木 圭子, 所 千晴

    Journal of MMIJ : journal of the Mining and Materials Processing Institute of Japan   127 ( 12 ) 724 - 728  2011年11月

    CiNii

  • Removal of borate with magnisium oxides prepared at different temperatures

    S. Moriyama, K. Sasaki, H. Yoshizaka, T. Hirajima

    GEOCHIMICA ET COSMOCHIMICA ACTA   74 ( 12 ) A726 - A726  2010年06月

    研究発表ペーパー・要旨(国際会議)  

  • Sorption and speciation of arsenic by zero-valent iron

    K. Sasaki, H. Nakano, W. Wilopo, Y. Miura, T. Hirajima

    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS   347 ( 1-3 ) 8 - 17  2009年09月

     概要を見る

    Sorption and speciation of arsenic in groundwater remediation using zero-valent iron (ZVI) was investigated by batch and column experiments. In batch tests, arsenite was oxidized to arsenate which was favorably immobilized by co-precipitation with Fe(III)-bearing compounds as corrosion products, leading to the dominant surface species of As(V). In column materials after introducing influent with arsenite for 22 pore volumes(pvs), As(III) was predominant on the surface of ZVI in all segments of column, while intense oxidation of arsenite to arsenate was observed especially near the inlet. It is considered that the surface of ZVI granules was already uniformed and corrosion products are the most accumulated on ZVI granules near the inlet because ZVI has been contacted with high concentrations of arsenite for the longest time in the most bottom parts. This was also supported by the experimental results of XPS that relative intensity of O 1s peak assigned to oxide was the largest in the most bottom segment. Also XPS results revealed that arsenic was immobilized on ZVI granules mainly as arsenite and to a lesser extent arsenate. These observations suggest that the retention mechanism is primarily sorption rather than reduction. The results of geochemical calculations along with the SEM-EDX suggest that arsenite and arsenate were co-precipitated with mainly Fe(III)-bearing minerals and carbonates. (C) 2008 Elsevier B.V. All rights reserved.

    DOI

  • Acidithiobacillus ferrooxidansヒ素耐性株によるenargiteのバイオリーチング過程での鉱物表面分析

    高次晃一郎, 笹木圭子, 平島剛, 大貫敏彦, TUOVINEN Olli H

    資源・素材学会春季大会講演集   ( 2 ) 81 - 82  2009年03月

    J-GLOBAL

  • Raman characterization of secondary minerals formed during chalcopyrite leaching with Acidithiobacillus ferrooxidans

    K. Sasaki, Y. Nakamuta, T. Hirajima, O. H. Tuovinen

    HYDROMETALLURGY   95 ( 1-2 ) 153 - 158  2009年01月

     概要を見る

    Chalcopyrite passivation greatly reduces the yields from leaching and bioleaching but the problem has not been successfully resolved. Passivation involves the formation of a layer of secondary minerals on chalcopyrite surface, which becomes a diffusion barrier to fluxes of reactants and products. This study aims to identify secondary minerals formed during chalcopyrite passivation in the presence of iron- and sulfur-oxidizing bacteria (Acidithiobacillus ferrooxidans) in mineral salts solution. The minerals were characterized with X-ray diffraction, Fourier transform-infrared spectroscopy, and Raman spectroscopy. Potassium jarosite was the initial product covering chalcopyrite grains, followed by the formation of ammonio-jarosite. Covellite and elemental sulfur were also detected in the passivation layer. The results suggest that passivation may be reduced by controlling jarosite precipitation and prior acclimatization of bacteria to oxidize CuS and elemental S in the presence of ferrous and ferric iron. (C) 2008 Elsevier B.V. All rights reserved.

    DOI CiNii

  • 北海道上ノ国人工湿地における重金属処理―重金属の土壌への固定形態と土壌微生物の役割―

    笹木 圭子, 堀 修, 荻野 激, 高野 敬志, 遠藤 祐司, 恒川 昌美, 平島 剛

    Journal of MMIJ   125 ( 8 ) 445 - 452  2009年

    DOI CiNii

  • Treatment of arsenate in acid mine drainage by a permeable reactive barrier bearing granulated blast furnace slag: Column study

    K. Sasaki, S. Nukina, W. Wilopo, T. Hirajima

    GEOCHIMICA ET COSMOCHIMICA ACTA   72 ( 12 ) A824 - A824  2008年07月

    研究発表ペーパー・要旨(国際会議)  

  • Formation of the Asian Center for Research on Earth Resources and Environment for International Research Associates and Graduate Students - JSPS International Training Program at Kyushu University-

    Kyuro Sasaki, Kenji Jinno, Tetsuro Esaki, Koichiro Watanabe, Takayuki Shimaoka, Keiko Sasaki

    Annual Report of Faculty of Engineering, Kyushu University   2008   45 - 49  2008年07月  [招待有り]

    記事・総説・解説・論説等(大学・研究所紀要)  

     概要を見る

    The JSPS project &quot;Formation of the Asian Center for Research on Earth Resources and Environment for International Research Associates and Graduate Students -JSPS International Training Program at Kyushu Universityー&quot; was introduced.

  • 湿式選別法を用いた石炭燃焼灰からの中空球形粒子の回収

    平島 剛, 大迫 雄司, 野中 壯泰, PETRUS H. T. B. M., 笹木 圭子, 安藤 隆

    Journal of MMIJ : journal of the Mining and Materials Processing Institute of Japan   124 ( 12 ) 878 - 884  2008年

     概要を見る

    Fly ash is a by-product in coal power plants and a rich source of hollow and spherical particles. Hollow and spherical particles having density less than 1 g/cm3 are known as cenospheres. Their concentration in coal fly ash is around 1%. Particles are widely used as fillers and insulators with high performances in rubber, plastics, oil industry, space industry, glass steels, etc. due to their shape, specific surface, excellent physical and chemical properties; as a consequence, their value is relatively high. However, hollow and spherical particles are filled up with N2 and/or CO2 gas bubbles so their densities can vary from 0.6g/cm3 to near or greater than 2.0 g/cm3. Fly ash can consist of more than 80% hollow and spherical particles having particle diameter less than several hundred μm and density less than 2.0 g/cm3, but there is no efficient and economic way to selectively recover them.<BR> The authors study on the recovery of cenospheres and hollow and spherical particles having density more than 1 g/cm3 from coal fly ash using a two-inch hydrocyclone and laboratory/pilot scale Mozley multi-gravity separator(MGS). A two-inch hydrocylone having 6.4 mm of spigot diameter was used to effectively concentrate cenospheres in overflow product. A very small amount of cenospheres having density less than 1 g/cm3 were recovered as a float of overflow product. Underflow product and overflow product without cenospheres were supplied to MGS and the influence of MGS parameter such as drum rotation speed and wash water rate was studied. As a result, 54% of hollow and sphercal particles having 2.08 g/cm3 of density and 61.6 μm of median diameter in underflow product was recovered as MGS lighter product and 17% of hollow and sphercal particles having 2.19 g/cm3 of density and 8.4 μm of median diameter in overflow product was recovered as MGS lighter product. These results show that hollow and spherical particles having median diameter less than one hundred μm with middle density can be recoverd.

    DOI CiNii

  • REMOVAL OF ARSENIC AND MANGANESE IN GROUNDWATER BY PERMEABLE REACTIVE BARRIER USING ZERO VALENCE IRON AND SHEEP MANURE

    WILOPO Wahyu, SASAKI Keiko, HIRAJIMA Tsuyoshi

    春季大会講演集. I, 資源編   19 ( 2 ) 127 - 128  2007年03月

    CiNii

  • 鉄粉を含む透過型浄化壁による地下水中の亜ヒ酸の不動化機構

    笹木 圭子, 中野 紘伸, 平島 剛, 三浦 好典

    春季大会講演集. I, 資源編   19 ( 2 ) 125 - 126  2007年03月

    CiNii

  • BIOFLOTATION OF SOME OXIDE MINERALS USING SIP-E. COLI

    FARAHAT MOHSEN, HIRAJIMA TSUYOSHI, SASAKI KEIKO, AIBA YUUKI

    春季大会講演集. I, 資源編   19 ( 2 ) 47 - 48  2007年03月

    CiNii

  • 亜臨界、超臨界条件下における孟宗竹水熱処理

    平島 剛, 矢吹 順平, 野中 壯泰, 笹木 圭子

    春季大会講演集. I, 資源編   19 ( 2 ) 43 - 44  2007年03月

    CiNii

  • 水熱処理によるバイオマス油化の触媒添加効果

    野中 壯泰, 平島 剛, 矢吹 順平, 笹木 圭子

    春季大会講演集. I, 資源編   19 ( 2 ) 41 - 42  2007年03月

    CiNii

  • 地下水中の亜ヒ酸のPRBによる不動化

    笹木 圭子, 中野 紘伸, 平島 剛

    春季大会講演集. I, 資源編   18 ( 2 ) 175 - 176  2006年03月

    CiNii

  • マンガン酸化真菌による生体鉱物へのコバルトイオンの吸着

    笹木 圭子, 松田 稔, 平島 剛, 金野 英隆

    春季大会講演集. I, 資源編   18 ( 2 ) 187 - 188  2006年03月

    CiNii

  • ARSENIC CONTAMINATION IN GROUNDWATER AT BUYAT, NORTH SULAWESI, INDONESIA

    WILOPO Wahyu, HENDRAYANA Heru, SASAKI Keiko, HIRAJIMA Tsuyoshi

    春季大会講演集. I, 資源編   18 ( 2 ) 169 - 170  2006年03月

    CiNii

  • Recovery of Cenospheres from Coal Fly Ash

    FARAHAT Mohsen, NONAKA Moriyasu, HIRAJIMA Tsuyoshi, SASAKI Keiko, YAMASHITA Toru, ANDO Takashi

    春季大会講演集. I, 資源編   18 ( 2 ) 137 - 138  2006年03月

    CiNii

  • アルカリ水熱処理におけるバイオマスの分解挙動

    野中 壯泰, 柿添 亮平, 平島 剛, 笹木 圭子, 鶴井 雅夫, 土屋 富士雄, 末武 悟

    春季大会講演集. I, 資源編   18 ( 2 ) 11 - 12  2006年03月

    CiNii

  • 水熱処理による低品位炭・木質系バイオマスの混合燃料化 : 混合比率の燃料化に及ぼす影響

    野中 壯泰, 平島 剛, 柿添 亮平, 笹木 圭子, 土屋 富士雄, 鶴井 雅夫

    春季大会講演集. I, 資源編   17 ( 2 ) 17 - 18  2005年03月

    CiNii

  • 連続式水熱処理装置による低品位炭・木質系バイオマスの混合燃料化

    平島 剛, 柿添 亮平, 野中 壯泰, 笹木 圭子, 土屋 富士雄, 鶴井 雅夫

    春季大会講演集. I, 資源編   17 ( 2 ) 19 - 20  2005年03月

    CiNii

  • マンガン酸化真菌による生体鉱物の合成と特性化

    笹木 圭子, 松田 稔, 平島 剛, 高野 敬志, 金野 英隆

    春季大会講演集. I, 資源編   17 ( 2 ) 11 - 12  2005年03月

    CiNii

  • 旧精進川鉱山における河川水および懸濁物質中のヒ素の挙動

    恒川 昌美, 小野寺 龍, 遠藤 祐司, 荻野 激, 笹木 圭子

    春季大会講演集. I, 資源編   17 ( 2 ) 39 - 40  2005年03月

    CiNii

  • 下水汚泥からのリン資源回収システムの開発(第2報) : 磁力選別によるリン品位の向上

    平島 剛, 巨瀬 未愛, 笹木 圭子, 萩野 隆生

    春季大会講演集. I, 資源編   17 ( 2 ) 175 - 176  2005年03月

    CiNii

  • 透過型反応浄化壁による地下水中のセレンの不動化

    笹木 圭子, ブロウズ デビッド, パチェック キャロル

    春季大会講演集. I, 資源編   17 ( 2 ) 153 - 154  2005年03月

    CiNii

  • 地下水・土壌におけるセレンの動態

    笹木 圭子

    春季大会講演集. I, 資源編   17 ( 1 ) "企画 - 87"-"企画-90"  2005年03月

    CiNii

  • 炭素繊維によるマンガン酸化真菌の活性化 : 繊維状であることの重要性

    金野 英隆, 遠藤 真衣, 橘 英樹, 笹木 圭子

    炭素   215   246 - 248  2004年11月

    CiNii

  • 硫酸還元菌による Metastable γ-MnS の合成

    柳 庚槿, 笹木 圭子, 広吉 直樹, 恒川 昌美

    春季大会講演集. I, 資源編   16 ( 2 ) 153 - 154  2004年03月

    CiNii

  • 雨鱒川懸濁物質におけるヒ素固定形態の連続抽出法による解明

    笹木 圭子, 小野寺 龍, 遠藤 祐司, 荻野 激, 恒川 昌美

    春季大会講演集. I, 資源編   16 ( 2 ) 73 - 74  2004年03月

    CiNii

  • 酸性環境における硫ヒ鉄鉱の溶解メカニズムに関する研究

    富岡 祐一, 広吉 直樹, 恒川 昌美, 笹木 圭子

    春季大会講演集. I, 資源編   16 ( 2 ) 65 - 66  2004年03月

    CiNii

  • Fundamental study on the removal of Mn2+ in acid mine drainage using sulfate reducing bacteria

    Kyoungkeun Yoo, Keiko Sasaki, Naoki Hiroyoshi, Masami Tsunekawa

    Materials Transactions   45 ( 7 ) 2422 - 2428  2004年01月

     概要を見る

    The optimum conditions for Mn2+ removal from acid mine drainage was studied by a SRB (sulfate reducing bacteria) bioreactor. Chemical experiments with Na2S as a S2- source were conducted to investigate the effects of pH, coexisting metal ions, and the components in a growth medium for SRB on MnS formation from Mn2+ solutions. The amount of Mn removed from the Mn2+ solutions decreased with decreasing pH. The Zn2+ or Fe2+ coexisting in the solutions consumed S2- by forming ZnS or FeS, and this inhibited Mn removal. Sodium citrate, a component of the growth medium for SRB, formed a complex with Mn2+ and suppressed MnS formation. Biological experiments using the SRB reactor were carried out at 37°C and it was confirmed that the Mn2+ concentration decreased to less than 10 g.m-3 from 100g.m-3 at neutral pHs (pH 5-7) after 100 hours when other metal ions and sodium citrate were absent. The formed precipitate was identified to be metastable γ-MnS with a band gap of about 3.8 eV by XRD, XRF, and UV-VIS.

    DOI CiNii

  • The effect of Mn2+ concentration on Mn removal by a sulfate reducing bacteria bioreactor

    Kyoungkeun Yoo, Keiko Sasaki, Naoki Hiroyoshi, Masami Tsunekawa, Tsuyoshi Hirajima

    Materials Transactions   45 ( 7 ) 2429 - 2434  2004年01月

     概要を見る

    In the design of sulfate reducing bacteria (SRB) bioreactors to remove metal ions from acid mine drainage, the tolerance of bacteria to metal ions is an important factor. The present study investigated the effects of Mn 2+ concentration on the growth and Mn removal activity of SRB in mediums containing 100-600 g.m-3 Mn2+. The Mn 2+ adsorbed on SRB cells and weakened the ability of bacterial sulfate reduction. However, the suppressive effect of Mn2+ on SRB growth can be disregarded, and 200 g.m-3 of Mn2+ in solution was removed, satisfying the requirement of the maximum contaminant level (MCL) of environmental water quality in Japan.

    DOI CiNii

  • Field study on heavy metal accumulation in a natural wetland receiving acid mine drainage

    K Sasaki, T Ogino, Y Endo, K Kurosawa

    MATERIALS TRANSACTIONS   44 ( 9 ) 1877 - 1884  2003年09月

     概要を見る

    The mechanism of surface water remediation in a natural wetland that is receiving heavy metal-rich acidic mine drainage was investigated. selective sequential extraction was useful to derive the mechanisms of heavy metal removal in the wetland. In the upstream portion of the Nvetland. dissolved Fe was removed mainly as oxide-bounded mineral phases. such as hydroxides. These are important for the subsequent removal of other heavy metals. Other ion-exchangeable and carbonate-bounded heavy metals are also observed in the upstream, associated with Fe oxides. Organic matter and Fe-Mn oxides in the upstream remove Cu and Zn ions from the drainage, respectively. In the middle of portion of the wetland the removal of heavy metal ions in relatively low concentrations occurs by the emergent vegetation. Greater clay abundance and higher microbial activity of sulfate reducing bacteria in the downstream parts achieved low-level removal of metals. Multi-cell wetlands are recommended for the treatment of acidic metal bearing surface water drainage, if sufficient land area and expenses are available to construct.

    DOI

  • A. ferrooxidans による硫ヒ鉄鉱の溶解に及ぼす諸要因の影響

    富岡 祐一, 広吉 直樹, 恒川 昌美, 平島 剛, 笹木 圭子

    春季大会講演集. I, 資源編   15 ( 2 ) 171 - 172  2003年03月

    CiNii

  • Desulfovibrio desulfuricans による中性pH領域におけるMn(II)イオン除去の最適化

    柳 庚槿, 笹木 圭子, 恒川 昌美

    春季大会講演集. I, 資源編   15 ( 2 ) 173 - 174  2003年03月

    CiNii

  • 人工湿地の生態系を利用した重金属汚染水の浄化に関する研究

    笹木 圭子, 堀 修, 荻野 激, 遠藤 祐司, 恒川 昌美

    春季大会講演集. I, 資源編   15 ( 2 ) 179 - 180  2003年03月

    CiNii

  • Chemical transportation of heavy metals in the constructed wetland impacted by acid drainage

    K Sasaki, T Ogino, O Hori, Y Endo, K Kurosawa, M Tsunekawa

    MATERIALS TRANSACTIONS   44 ( 2 ) 305 - 312  2003年02月

     概要を見る

    Chemical transportation of heavy metals in the constructed wetland impacted by acid drainage was investigated seasonally using a combination of the selective sequential extraction of the sediments with elemental analysis of the emergent vegetation in the wetland. Manganese was dissolved from sediments in the constructed wetland by the contact with acid drainage, and then precipitated again as ion-exchangeable forms. It was expected that a part of Mn and Fe bound to oxides were flown out of the wetland as suspended particulate matters. It was observed that there is passive absorption of Mn in leaves of Phragmites austlaris in the upstream of the wetland. The transportation of Cu clearly showed the seasonal variation: there was the decomposition of organic substances with high molecular weights by soil microorganisms in summer. Therefore, Cu was complexed to the humic substances, and dramatically adosorbed onto the roots of Phragmites austlaris in down stream of the wetland. It was also observed that there is active absorption of Fe in roots and leaves of Phragmites austlaris. Most of the zinc was strongly bounded to the sediments, therefore, scarcely uptaken to the vegetation. It was also found that there were heavy metal distributions between plant organs.

    DOI

  • Promoting effect of carbon fiber on the biological oxidation of dissolved Mn(II) ions in water

    Proceedings of International Symposium on Carbon    2003年

  • Accumulation of heavy metals in the emergent vegetations in the constructed wetland

    Proceedings of the 16th International Symposium on Environmental Biogeochemistry    2003年

  • Biological synthesis of metastable g-MnS by sulfate reducing bacteria

    Proceedings of the Japan/Korea International Symposium on Resources Recycling and Material Sciences    2003年

  • Removal of Mn(II) ions by manganese-oxidizing fungus at neutral pHs in the presence of carbon fiber

    Proceedings of International Biohydrometallurgy Symposium    2003年

  • Acidithiobacillus ferrooxidansによる硫ひ鉄鉱の溶解と有機酸による抑制に関する研究

    笹木 圭子, 富岡 祐一, 平島 剛, 恒川 昌美

    Shigen-to-Sozai   119, 61-65 ( 2 ) 61 - 65  2003年

     概要を見る

    Microbially mediated dissolution of arsenopyrite by Acidithiobacillus ferrooxidans and its suppression by two kinds of organic matters was investigated. Results are summarized as follows:<BR>(1) In the microbially mediated dissolution of arsenopyrite by Acidithiobacillus ferrooxidans, the dissolved arsenic species inhibited the growth and activity of the microorganism, therefore, the dissolution rate was slow in comparison with those of pyrite.<BR>(2) In the presence of low concentrations of tannic acid, the growth and activity of the A. ferrooxidans were not inhibited but accelerated.<BR>(3) The presence of extractant after autoclaving Acacia Mangium, which contains trace amounts of poly-phenolic derivatives, leads the fast consumption of oxygen and strongly reducing function, therefore, quickly inhibited the first oxidation of arsenopyrite by oxygen. It is fairly different from the suppression mechanism by tannic acid.

    DOI CiNii

  • 水熱処理による木質系バイオマス燃料製造に関すル基礎的研究

    平島 剛, 小林 弘幸, 湯川 健太郎, 恒川 昌美, 福嶋 正巳, 笹木 圭子, 大里 克明, 須藤 良考

    資源と素材   119, 118-124 ( 3 ) 118 - 124  2003年

     概要を見る

    Woody biomass (Acacia Mangium) which contains 43 % (dry basis) of oxygen was converted by treatment in liquid water at temperature ranging from 270 to 350 &deg;C, pressures 8.3 to 18.4 MPa, and holding time 10 minutes using an autoclave of 10 l capacity. At these reaction conditions a significant proportion of the oxygen was removed and the oxygen content of the solid product became 14-24 %. Oxygen removal increased the carbon content and the heating value, leading to a product with more sub-bituminous and bituminous coal-like properties. This solid product having heating values of 6,900-7,160 kcal / kg (dry basis) is an excellent fuel because of its higher volatile matter content, low sulfur and low ash. After cooling down the reaction mixture to ambient temperatures, the liquid product containing the organic components was dissolved in the process water. It is composed of mainly methyl alcohol, acetic acid, components derived from cellulose and hemi-cellulose such as 5-hydroxymethyl-2-furancarboxaldehyde and furfural, and lignin components such as 2, 6-dimethoxy-phenol and guaiacol. The mechanism of the conversion process is discussed through Fourier Transform Infrared Spectroscopy, Gas Chromatograph Mass Spectroscopy and Fluorescence Spectroscopy analysis results.

    DOI CiNii

  • Chemical transportation of heavy metals in the constructed wetland impacted by acid drainage

    Keiko Sasaki, Tagiru Ogino, Osamu Hori, Yuji Endo, Kunihiko Kurosawa, Masami Tsunekawa

    Materials Transactions   44 ( 2 ) 305 - 312  2003年

     概要を見る

    Chemical transportation of heavy metals in the constructed wetland impacted by acid drainage was investigated seasonally using a combination of the selective sequential extraction of the sediments with elemental analysis of the emergent vegetation in the wetland. Manganese was dissolved from sediments in the constructed wetland by the contact with acid drainage, and then precipitated again as ion-exchangeable forms. It was expected that a part of Mn and Fe bound to oxides were flown out of the wetland as suspended particulate matters. It was observed that there is passive absorption of Mn in leaves of Phragmites austlaris in the upstream of the wetland. The transportation of Cu clearly showed the seasonal variation: there was the decomposition of organic substances with high molecular weights by soil microorganisms in summer. Therefore, Cu was complexed to the humic substances, and dramatically adsorbed onto the roots of Phragmites austlaris in down stream of the wetland. It was also observed that there is active absorption of Fe in roots and leaves of Phragmites austlaris. Most of the zinc was strongly bounded to the sediments, therefore, scarcely uptaken to the vegetation. It was also found that there were heavy metal distributions between plant organs.

    DOI

  • Analysis of heavy metals in a tailing impoundment of abandoned Mn mine by using two sequential extractions

    K Yoo, K Sasaki, T Hirajima, M Tsunekawa

    MATERIALS TRANSACTIONS   43 ( 12 ) 3189 - 3194  2002年12月

     概要を見る

    The tailing impoundment was investigated for vertical distribution of minerals by X-ray fluorescence analysis (XRF), powder X-ray diffraction (XRD), and two sequential extraction methods. It was found that Si, Mn, and Fe occupied over 80% in mass balance of XRF, and present as constituents of clay minerals, oxides, and pyrite, respectively. Therefore, the sampling site was regarded as chemically stable. Two sequential extraction methods were complementary to each other, therefore, the combination of two methods is useful for further analysis of sediments including variable minerals.

    DOI

  • Analysis of heavy metals in a tailing impoundment of abandoned Mn mine by using two sequential extractions

    K Yoo, K Sasaki, T Hirajima, M Tsunekawa

    MATERIALS TRANSACTIONS   43 ( 12 ) 3189 - 3194  2002年12月

     概要を見る

    The tailing impoundment was investigated for vertical distribution of minerals by X-ray fluorescence analysis (XRF), powder X-ray diffraction (XRD), and two sequential extraction methods. It was found that Si, Mn, and Fe occupied over 80% in mass balance of XRF, and present as constituents of clay minerals, oxides, and pyrite, respectively. Therefore, the sampling site was regarded as chemically stable. Two sequential extraction methods were complementary to each other, therefore, the combination of two methods is useful for further analysis of sediments including variable minerals.

    DOI

  • Removal of Manganese (Ⅱ) Ions from Water by Leptothrix Discophora with Carbon Fiber

    Materials Transactions   43 ( 11 ) 2773 - 2777  2002年11月

    DOI

  • Removal of manganese(II) ions from water by Leptothrix discophora with carbon fiber

    K Sasaki, M Endo, K Kurosawa, H Konno

    MATERIALS TRANSACTIONS   43 ( 11 ) 2773 - 2777  2002年11月

     概要を見る

    To apply manganese-oxidizing bacteria to waste water treatment, basic performance of the manganese-oxidizing bacterium, Leptothrix discophora, distributed by ATCC was examined. In addition, the effect of carbon fiber on the oxidation by the bacterium was also investigated, since carbon fiber was reported to accelerate the growth of activated sludge during sewage treatment. The bacterium was found to be active in the medium containing 24 ppm Mn(II) ions, the concentration being about 8 times higher than the recommended one and practically useful level. The oxidation rate was higher with the static culture than the shaking culture. This was considered to be due to physical damage to the sheath structure of bacteria which is reported to be important to oxidize Mn(II) ions. The carbon fiber did not accelerate the microbial oxidation of Mn(II) ions. This is partly attributed to the lack of contact between the bacterial cell, which floated as thin membranes, and the carbon fiber sunk in the bottom of vessels. However, oxidized Mn species precipitated on the carbon fiber, which resulted in an improvement of the transparency of water. This effect is different from the one caused by activated carbons, since the carbon fiber has very low specific surface area and no pore structure. The effect was more remarkable in the shaking culture than the static culture, indicating that organic substances originated from the bacterium play an important role in the adsorption of oxidized Mn species.

    DOI

  • 廃蛍光管からの希土類元素の再資源化とその有効利用に関する研究(第3報)

    平島 剛, 濱田 暢哉, 平井 宏尚, 恒川 昌美, 広吉 直樹, 笹木 圭子, 高橋 徹, 長野 伸泰

    春季大会講演集. I, 資源編   14 ( 2 ) 191 - 192  2002年03月

    CiNii

  • 低品位石炭改質時に生成する液体の六価クロム還元への利用

    湯川 健太郎, 平島 剛, 小林 弘幸, 恒川 昌美, 福嶋 正巳, 須山 千秋, 笹木 圭子

    春季大会講演集. I, 資源編   14 ( 2 ) 58 - 59  2002年03月

    CiNii

  • 酸性廃水を導入した人工湿地における重金属の固定形態

    笹木 圭子, 荻野 激, 堀 修, 遠藤 祐司, 黒沢 邦彦, 恒川 昌美

    春季大会講演集. I, 資源編   14 ( 2 ) 33 - 34  2002年03月

    CiNii

  • 中性領域における鉱廃水のマンガン除去に及ぼす共存イオンの影響

    柳 庚槿, 笹木 圭子, 恒川 昌美

    春季大会講演集. I, 資源編   14 ( 2 ) 35 - 36  2002年03月

    CiNii

  • マンガン酸化真菌を利用した水質浄化と炭素繊維の効果

    遠藤 真衣, 笹木 圭子, 金野 英隆

    春季大会講演集. I, 資源編   14 ( 2 ) 9 - 10  2002年03月

    CiNii

  • 微生物を媒介とした硫砒鉄鉱の溶解に及ぼす有機酸の影響

    笹木 圭子, 富岡 祐一, 平島 剛, 恒川 昌美

    春季大会講演集. I, 資源編   14 ( 2 ) 13 - 14  2002年03月

    CiNii

  • 加圧熱水処理によるバイオマス燃料製造と生成液体の有効利用

    平島 剛, 小林 弘幸, 湯川 健太郎, 恒川 昌美, 笹木 圭子, 福嶋 正巳, 須山 千秋, 片桐 務, 須藤 良考

    春季大会講演集. I, 資源編   14 ( 2 ) 84 - 85  2002年03月

    CiNii

  • マンガン酸化物の堆積が認められる北海道内湧水の水質の比較

    高野 敬志, 伊藤 八十男, 泉 敏彦, 鈴木 智宏, 黒沢 邦彦, 遠藤 祐司, 荻野 激, 野呂田 晋, 笹木 圭子

    北海道立衛生研究所報   ( 52 ) 99 - 101  2002年

     概要を見る

    北海道十勝地方の足寄町に所在する湯の滝には天然で大規模なマンガン酸化物の堆積が認められる。ここでは、地表におけるマンガン酸化物の形成がマンガン酸化菌と微小藻類との複合的な働きにより行われていることが推定されており、このようなマンガン酸化物の生成過程は世界的にも珍しいことから、国の天然記念物に指定されている。さらに、湯の滝ほど大規模ではないが、北海道内にはほかにもマンガン酸化物の堆積が認められる水域が存在している。その一つは渡島地方の森町に所在する駒の湯で、湧水の流水路の壁にマンガン酸化物の堆積が認められている。また、後志地方の古平町に所在する稲倉石鉱山において、噴出している廃水を受ける槽の底部にマンガン酸化物の堆積が認められている。駒の湯及び稲倉石鉱山廃水は、その水質から判断すると、化学的にマンガンが酸化されているとは考えにくく、マンガン酸化物の堆積には微生物の関与があると推定される。一般に水生微生物の生育には水質が影響することから、これら3地点のマンガン酸化物形成に対して、水質の影響を無視することはできない。今回はこれら3地点の水質の比較をすることにより、微生物によるマンガン酸化物の形成の特徴を推定した。

    CiNii

  • Acid-sequential extraction for core-samples in mine tailing dumps.

    Materials Transactions   43(12)、3189-3194  2002年

    DOI

  • Synthesis of Aragonite from Calcined Scallop Shells at Ambient Temperatures and Their Morphological Characterization by FE-SEM

    笹木 圭子, 山下 知彦, 恒川 昌美

    Shigen-to-Sozai   118, 553-558 ( 8 ) 553 - 558  2002年

     概要を見る

    常温において,CO2 流速を制御しMg2+ イオン共存下で,ホタテ貝殻焼成物からアラゴナイトが合成できた。Mg2+ イオンは大部分が溶液中に残存し,あたかも一種の触媒のように振る舞うかにみえたが,ごく少量は微細なカルサイト結晶の表面に特異的に吸着し,カルサイトの結晶成長を妨害する働きをしていた。FE-SEM観察によって,アラゴナイトの形態およびサイズは反応温度に鋭敏に影響を受けることがわかった。原料を石灰石とした場合と比較すると,ホタテ貝殻から合成したアラゴナイトは凝集しやすい傾向がみられた。本研究によって,廃ホタテ貝殻のより高度な用途開発が可能となり,しかも微粒のアラゴナイト結晶の常温合成,いわゆるソフトプロセスが可能であることが明らかとなった。

    DOI CiNii

  • Acid-sequential extraction for core-samples in mine tailing dumps.

    Materials Transactions   43(11), in press  2002年

  • 常温におけるホタテ貝殻焼成物からのアラゴナイトの合成とFE-SEMによるそれらの形態特性

    笹木 圭子, 山下 知彦, 恒川 昌美

    資源と素材 : 資源・素材学会誌 : journal of the Mining and Materials Processing Institute of Japan   118, 553-558 ( 8 ) 553 - 558  2002年

     概要を見る

    常温において,CO2 流速を制御しMg2+ イオン共存下で,ホタテ貝殻焼成物からアラゴナイトが合成できた。Mg2+ イオンは大部分が溶液中に残存し,あたかも一種の触媒のように振る舞うかにみえたが,ごく少量は微細なカルサイト結晶の表面に特異的に吸着し,カルサイトの結晶成長を妨害する働きをしていた。FE-SEM観察によって,アラゴナイトの形態およびサイズは反応温度に鋭敏に影響を受けることがわかった。原料を石灰石とした場合と比較すると,ホタテ貝殻から合成したアラゴナイトは凝集しやすい傾向がみられた。本研究によって,廃ホタテ貝殻のより高度な用途開発が可能となり,しかも微粒のアラゴナイト結晶の常温合成,いわゆるソフトプロセスが可能であることが明らかとなった。

    DOI CiNii

  • ホタテ貝殻の資源化のための技術開発 : 繊維状 aragonite の合成

    笹木 圭子, 小林 弘幸, 恒川 昌美

    資源・素材   2001   16 - 16  2001年09月

    CiNii

  • 低品位炭改質時に生成する液体の有効利用に関する研究

    湯川 健太郎, 平島 剛, 恒川 昌美, 福嶋 正巳, 笹木 圭子

    資源・素材   2001   15 - 15  2001年09月

    CiNii

  • 物理選別による廃蛍光管からの希土類蛍光体回収

    平井 宏尚, 平島 剛, 恒川 昌美, 広吉 直樹, 中山 和久, 笹木 圭子, 高橋 徹, 長野 伸泰

    資源・素材   2001   27 - 27  2001年09月

    CiNii

  • 休廃止鉱山の鉱滓堆積場におけるコア中の鉱物の鉛直分布

    笹木 圭子, 平島 剛, 芳賀 生憲, 黒沢 邦彦, 恒川 昌美

    資源処理技術 : 浮選 = Resources processing   48 ( 2 ) 75 - 84  2001年06月

    CiNii

  • 坑内水に由来する各種重金属イオンの湿地における固定形態

    笹木 圭子, 柳 庚槿, 荻野 激, 遠藤 祐司, 黒沢 邦彦, 恒川 昌美

    一般発表(研究・業績発表)講演要旨集   2001 ( 2 ) 231 - 232  2001年03月

    CiNii

  • 酸連続抽出法による休廃止Mn鉱山の鉱滓堆積場における各種重金属の状態分析

    柳 庚槿, 笹木 圭子, 青柳 宏樹, 平島 剛, 恒川 昌美

    一般発表(研究・業績発表)講演要旨集   2001 ( 2 ) 233 - 234  2001年03月

    CiNii

  • 廃蛍光管からの希土類元素の再資源化とその有効利用に関する研究(第2報) : 湿式及び乾式選別による希土類蛍光体の回収

    平島 剛, 平井 宏尚, 中山 和久, 恒川 昌美, 広吉 直樹, 笹木 圭子, 高橋 徹, 長野 伸泰

    一般発表(研究・業績発表)講演要旨集   2001 ( 2 ) 10 - 11  2001年03月

    CiNii

  • Morphologies of aragonite synthesized from scallop shells and lime stones by successive reaction.

    Proc. 6th Intl. Symp. East Asian Recycling Technology   331-336  2001年

  • Bioaccumulation of manganese for water treatment with carbon fiber.

    Proc. Intl. Symp. BIOMINE '2001   279-286  2001年

  • ホタテ貝殻と石灰石を原料としたaragoniteの合成‐逐次反応による形態制御‐

    笹木 圭子, 小林 弘幸, 恒川 昌美

    資源と素材   117, 747-752 ( 9 ) 747 - 752  2001年

     概要を見る

    Aragonite-type of light calcium carbonate was synthesized by the successive reaction using calcined-hydrous scallop shells and calcined lime stones in the aqueous system with Mg2+ ions under the CO2 bubbling. In order to obtain the high aspect ratios of aragonite, the reaction temperature and concentrations of Ca2+ ions in the 2nd step were important. The aspect ratio of aragonite increased when the reaction temperature was higher in the 2nd step than in the 1st step of the successive reaction. When the smaller amounts of calcium source were added in the 2nd step than in the 1st step, and the reaction temperature was lower in the 2nd step than in the 1st step, large particles of aragonite were produced with no smooth surfaces. The successive reaction was useful to extend the variety of morphologies in aragonite.

    DOI CiNii

  • 休廃止鉱山の鉱濘堆積場における鉛通コアの鉱物分布

    資源処理技術   48, 75-84  2001年

    DOI

  • Morphologies of aragonite synthesized from scallop shells and lime stones by successive reaction.

    Proc. 6th Intl. Symp. East Asian Recycling Technology   331-336  2001年

  • Bioaccumulation of manganese for water treatment with carbon fiber.

    Proc. Intl. Symp. BIOMINE '2001   279-286  2001年

  • 浮選による廃蛍光体からの希土類蛍光体の回収

    平島 剛, 中山 和久, 恒川 昌美, 広吉 直樹, 笹木 圭子, 高橋 徹, 長野 伸泰

    廃棄物学会研究発表会講演論文集 = Proceedings of the Annual Conference of the Japan Society of Waste Management Experts   11 ( 1 ) 495 - 497  2000年10月

    CiNii

  • 廃ホタテ貝殻から機能性カルシウム素材への転換

    笹木 圭子, 恒川 昌美

    廃棄物学会研究発表会講演論文集 = Proceedings of the Annual Conference of the Japan Society of Waste Management Experts   11 ( 1 ) 423 - 425  2000年10月

    CiNii

  • 鉱業のためのバイオレメディエーション

    笹木 圭子

    資源・素材   2000 ( 3 ) 133 - 136  2000年10月

    CiNii

  • 酸連続抽出法による鉱滓堆積コアの鉱物種および構成重金属の鉛直分布解析

    笹木 圭子, 平島 剛, 芳賀 生憲, 恒恒川 昌美

    一般発表(研究・業績発表)講演要旨集   2000 ( 2 ) 223 - 225  2000年03月

    CiNii

  • 廃蛍光管からの希土類元素の再資源化とその有効利用に関する研究 -希土類蛍光体の回収-

    平島 剛, 中山 和久, 恒川 昌美, 広吉 直樹, 笹木 圭子, 高橋 徹, 長野 伸泰

    一般発表(研究・業績発表)講演要旨集   2000 ( 2 ) 169 - 170  2000年03月

    CiNii

  • Morphology of jarosite-group compounds precipitated from biologically and chemically oxidized Fe ions

    K Sasaki, H Konno

    CANADIAN MINERALOGIST   38 ( 1 ) 45 - 56  2000年02月

     概要を見る

    Jarosite-group compounds [MFe(3)(SO(4))(2)(OH)(6): argentojarosite (M(+) = Ag(+)),jarosite (M(+) = K(+)), ammoniojarosite (M(+) = NH(4)(+))] were synthesized by supplying Fe(3+) ions in three different ways: biological oxidation of Fe(2+) ions by T. ferrooxidans (biological products), chemical oxidation of Fe(2+) ions by slow addition of H(2)O(2) (chemical products 1), and chemical oxidation by rapid addition of H(2)O(2) (chemical products 2). These were characterized by XRD, FTIR chemical analysis and SEM; as well, the morphological features were compared with those formed by the hydrothermal method (standard substances). The jarosite-group compounds so synthesized do not contain crystalline by-products, as revealed by XRD, but the order of purity inferred from IR spectra, which is determined by the intensity of specific peaks, was found to be dependent on the method of preparation and is independent of the jarosite species; the order was found to be standard substances &gt; chemical products 2 &gt; chemical products 1 &gt; biological products. Two main factors were found to affect the morphology, the method and rate of supply of Fe(3+) ions to the system and the nature of the monovalent cations, which determine the intrinsic rate of formation under given conditions. Where Fe(3+) ions are present in the system from the beginning, the order of rate of formation is confirmed to be argentojarosite &gt; jarosite &gt; ammoniojarosite at 30 degrees C. Morphological features of jarosite-group phases formed by the biological method were rendered distinguishable by the effect of extracellular substances. Morphological information is useful to distinguish the mode of occurrence of jarosite-group phases in natural samples, since it may be difficult to do so by other analytical techniques, such as XRD, FTIR Raman spectroscopy and chemical analysis.

    DOI CiNii

  • Water treatment of manganese-rich mine drainage by manganese-oxidizing bacteria at neutral pH

    SASAKI K

    Proceedings of the XXI International Mineral Processing Congress, July 23-27, 2000, Rome, Italy   B   18 - 24  2000年

    CiNii

  • 酸性環境における黄鉄鉱の溶解およびその抑制に関する研究

    笹木 圭子

    地球化学   33 ( 2 ) 139 - 139  1999年06月

    CiNii

  • Comparative studies of the reduction behavior of chromium(VI) by humic substances and their precursors

    K Nakayasu, M Fukushima, K Sasaki, S Tanaka, H Nakamura

    ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY   18 ( 6 ) 1085 - 1090  1999年06月

     概要を見る

    Hexavalent chromium (Cr[VI]) is reduced by dissolved organic carbons (DOCs) such as humic substances, tannic acid (TA), and gallic acid (GA). The kinetic constants and the resulting chemical species after the reduction were compared with each other. The kinetic constants for GA and TA, which are model precursors of humic substances, were two to three orders of magnitude larger than those for the humic substances when these kinetic constants were expressed as a function of the molar concentration of the reductive functional group (F-red) in various DOCs. After the reduction of Cr(VI), the percentages of the species complexed with GA and TA were higher than those with the humic substances. This appears to be due to the formation of high molecular weight compounds by polymerization during the reduction of Cr(VI) and complexation of Cr(III) with the polymerized compounds. The UV-vis spectrophotometric data and gel permeation chromatography support this view.

    DOI CiNii

  • 黄鉄鉱の風化における硫黄酸化細菌の役割

    笹木 圭子, 恒川 昌美

    一般発表(研究・業績発表)講演要旨集   1997 ( 1 ) 205 - 205  1999年03月

    CiNii

  • 廃ホタテ貝殻焼成物を原料としたアラゴナイト型軽質炭酸カルシウムの合成-非晶質炭酸カルシウムを中間体とする方法-

    笹木 圭子, 本郷 大, 恒川 昌美

    一般発表(研究・業績発表)講演要旨集   1997 ( 1 ) 124 - 124  1999年03月

    CiNii

  • 休廃止鉱山鉱滓堆積場における環境調査-鉛直方向の重金属および嫌気性菌の分布-

    笹木 圭子, 平島 剛, 芳賀 生憲, 恒川 昌美

    一般発表(研究・業績発表)講演要旨集   1999 ( 2 ) 201 - 202  1999年03月

    CiNii

  • 水溶性切削油剤の腐敗防止に関する研究

    平島 剛, 笹木 圭子, 芳賀 生憲, 大沼 英明, 恒川 昌美, 西尾 広志

    一般発表(研究・業績発表)講演要旨集   1999 ( 2 ) 199 - 200  1999年03月

    CiNii

  • Evaluation of copper(II) binding abilities of humic substances by a continuous site-distribution model considering proton competition

    M Fukushima, S Tanaka, K Nakayasu, K Sasaki, K Tatsumi

    ANALYTICAL SCIENCES   15 ( 2 ) 185 - 188  1999年02月

    DOI CiNii

  • 混合原子価モリブデンオキシ水酸化物皮膜の電析とそのキャラクタリゼーション

    金野 英隆, 伊東 隆史, 尾谷 賢, 笹木 圭子

    表面技術 = The Journal of the Surface Finishing Society of Japan   50 ( 10 ) 909 - 914  1999年

     概要を見る

    Dark brown oxyhydroxide films were formed on aluminum, copper, and, ITO glass by cathodic pulse electrolysis in a 0.016mol L-1(NH4)6Mo7O24-0.32molL-1MgSO4 solution of pH 5 at 50°C. The XPS and ICP-AES analyses indicated that the films were composed of mixed valence molybdenum ions of Mo (IV) to Mo (VI), Mg (II) ions, and small amounts of sulfate ions. The MgSO4 is a necessary component in the solution to obtain uniform and adhesive films. The NH4+, Na+ or Zn (II) ions substituted for Mg (II) ions, and acetate, nitrate or phosphate ions substituted for sulfate ions in the solution adversely affected the formation of uniform and adhesive films. Though the decrease of Mg (II) ions in the solution increased the amount of Mo ions in the film, it also showed adverse effects. The films were amorphous by XRD even after drying at 200°C for 12h. Diffuse reflectance spectra of films showed that transmittance is about 15% in the UV-VIS region of 200-700nm in wavelength and increases to 70-80% in the near IR region of 1.5-2μm. Spectrophtometric emissivity measurements at 100°C indicated that emissivity in the IR region of 4-10μm is around 40% and increases drastically to over 90% for wave length longer than 10μm. It indicaates that the film is a selective emitter/absorber for the far IR region. The film also showed electric conductivity.

    DOI CiNii

  • 「Cu錯体による水溶性切削剤中の硫酸還元菌の増殖および活性阻害に関する研究」

    笹木 圭子, 平島 剛, 大沼 英明, 芳賀 生憲, 恒川 昌美, 西尾 広志

    資源処理技術   46 ( 3 ) 153 - 160  1999年

    DOI CiNii

  • 水溶性切削油剤の腐敗防止に関する研究-銅錯体による硫酸還元細菌の生育阻害効果-

    平島 剛, 笹木 圭子, 芳賀 生憲, 大沼 英明, 恒川 昌美, 西尾 広志

    資源と素材   115 ( 4 ) 240 - 244  1999年

     概要を見る

    A major problem with water-based cutting fluids is bacterial propagation that can quickly ruin the fluid's effectiveness and cause rancid smell. Effects of copper triethanolamine (Cu-TEA) and copper ethylenediaminetetraacetic acid, disodium (Cu-EDTA) on the colony forming activity of sulfate-reducing bacteria (SRB) have been investigated. The copper complexes were prepared by direct addition of TEA or EDTA to the copper sulfate solution, or by electrolysis with copper electrode in complexing agent solutions. In the copper complexes, the mole ratio of copper ions to TEA or EDTA was 1:1, respectively. The growth of SRB was affected by the addition of Cu-TEA or Cu-EDTA and inhibited strongly at 0.1 mmol dm-3 copper concentration. From the data available, no obvious difference was observed between the copper complexes regarding the colony formation of SRB.

    DOI CiNii

  • 酸性環境における微生物を媒介とした黄鉄鉱の溶解に対する天然有機酸の阻害効果

    笹木 圭子, 恒川 昌美, 田中 俊逸, 福嶋 正巳, 金野 英隆

    資源と素材 : 資源・素材学会誌 : journal of the Mining and Materials Processing Institute of Japan   115 ( 4 ) 233 - 239  1999年

     概要を見る

    Natural organic acids, such as tannic acids (TA), wood vinegar (WV), fulvic acids (FA), and humic acids (HA), were investigated as suppressants of microbially mediated dissolution of pyrite with Thiobacillus ferrooxidans and Thiobacillus thiooxidans in acidic media at pH 2∼4, and the suppression mechanism is discussed. The suppression occurs by adsorption of natural organic acids on pyrite, inhibition of cell growth, as well as reduction and complexation of Fe(�) ions. Most of these factors are affected by pH:the suppression by FA was stronger at pH 2 than at pH 3∼4, because the affinity between pyrite and the aromatic groups in FA is stronger below the isoelectric point (iep) of pyrite (around pH 2.5). Cell growth was more strongly inhibited by natural organic acids at lower pH. The order of suppression was WV > TA >> FA > HA at all pHs here, and dependent on the number of functional groups, such as phenolic and carboxylic groups in the natural organic acids. The pKa of WV was ∼5.0, and the acid-base titration and elemental analysis suggested that WV contains acetic acid and large amounts of other organic acids. Wood vinegar was found to suppress and retard pyrite dissolution over a wide pH.

    DOI CiNii

  • ホタテ貝殻からのアラゴナイトの合成

    笹木 圭子, 恒川 昌美

    資源・素材   1998 ( 3 ) 99 - 102  1998年11月

    CiNii

  • Distinction of jarosite-group compounds by Raman spectroscopy

    K Sasaki, O Tanaike, H Konno

    CANADIAN MINERALOGIST   36   1225 - 1235  1998年10月

     概要を見る

    Raman spectra (200-1300 cm(-1)) were measured for synthesized jarosite-group compounds [MFe3(SO4)(2)(OH)(6), M+ = K+, NH4+, Na+, Ag+, and 1/2Pb(2+)). The Raman spectra of jarosite-group compounds are characterized by a tendency for the wavenumbers assigned to two vibrational modes of SO42-, nu(1)(SO42-) and nu(3)(SO42-), and three vibrational modes of Fe-O bonds, to decrease with increase in the c unit-cell parameter. The wavenumbers assigned to the nu(2)(SO42-) and nu(4)(SO42-) vibrational modes are independent of the value of c. For plumbojarosite, the peaks corresponding to the nu(1)(SO42-) and nu(3)(SO42-) vibrational modes are broad owing to two overlapping peaks assigned to two types of sulfate groups, SO42- ions adjacent and not adjacent to Pb2+ ions. Raman spectra can serve to identify the specific type of jarosite-group compound in poorly crystalline or low-concentration geochemical samples.

  • 黄鉄鉱の常温酸化溶解に関する実験地球化学的研究

    笹木 圭子

    鉱物学雜誌 = Journal of the Mineralogical Society of Japan   27 ( 2 ) 93 - 103  1998年05月

    CiNii

  • ホタテ貝殻を原料としたアラゴナイト型軽質炭酸カルシウムの常温合成

    笹木 圭子, 本郷 大, 恒川 昌美

    一般発表(研究・業績発表)講演要旨集   1998 ( 2 ) 102 - 102  1998年03月

    CiNii

  • 森林を起源とした天然有機酸による黄鉄鉱の微生物学的溶出の抑制とそのpH依存性

    笹木 圭子, 恒川 昌美

    一般発表(研究・業績発表)講演要旨集   1998 ( 2 ) 36 - 36  1998年03月

    CiNii

  • The role of sulfur-oxidizing bacteria Thiobacillus thiooxidans in pyrite weathering

    K Sasaki, M Tsunekawa, T Ohtsuka, H Konno

    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS   133 ( 3 ) 269 - 278  1998年02月

     概要を見る

    The role of the sulfur-oxidizing bacteria Thiobacillus thiooxidans in pyrite weathering was investigated to clarify the effects of the bacteria on the dissolution behavior of pyrite and the formation of secondary minerals using Raman spectroscopy and powder X-ray diffraction (XRD) in addition to solution analysis. It was found that T. thiooxidans, when present with the iron-oxidizing bacteria Thiobacillus ferrooxidans, enhanced the dissolution of Fe and S species from pyrite, whereas T. thiooxidans alone did not oxidize pyrite. Enhancement of the consumption of elemental sulfur and regeneration of Fe(II) ions were also observed with T. thiooxidans together with T. ferrooxidans, while this did not occur with T. ferrooxidans alone. It may be assumed that the contribution of T. thiooxidans to the formation of acid mine drainage on a geochemical scale should not be overlooked, though pyrite weathering is predominantly caused by iron-oxidizing activity in T. ferrooxidans. (C) 1998 Elsevier Science B.V.

    DOI CiNii

  • 「廃ホタテ貝殻焼成物を原料とするaragonite型軽質炭酸カルシウムの合成(第2報)ー種結晶としてaragonite型炭酸塩を用いる方法ー」

    笹木 圭子, 本郷 大, 恒川 昌美

    『資源と素材』   114 ( 10 ) 709 - 713  1998年

     概要を見る

    Aragonite-type calcium carbonate was synthesized from calcined scallop shell using carbonates of orthorohombic structure (such as SrCO3) as seeds, by bubbling CO2 at ambient temperature. The products were examined by FTIR, SEM, EPMA, and XRD. The addition of SrCO3 increased aragonite content in the products, but BaCO3 and PbCO3 did not play the role of seed crystals due to the difference of their lattice parameters to those of aragonite, whereas lattice parameters of SrCO3 are the most similar to them. With increasing SrCO3 -addition, formation of aragonite was accelerated to a limit in the amount. Light calcium carbonate rich in aragonite was formed in agglegates consisting of needle-like crystals with large specific surface areas.

    DOI CiNii

  • 「廃ホタテ貝殻焼成物を原料とするaragonite型軽質炭酸カルシウムの合成(第3報)―常温水溶液系における高純度aragoniteの生成―」

    笹木 圭子, 本郷 大, 恒川 昌美

    『資源と素材』   114 ( 10 ) 715 - 720  1998年

     概要を見る

    Aragonite-type light calcium carbonate was synthesized from calcined scallop shell at ambient temperature in the aqueous system with Mg2+ ions under the CO2 bubbling for 4 hours. The important factors to obtain high purity of aragonite were the mole ratio of Ca2+/ Mg2+, flow rate of CO2 , reaction time, pH and temperature. Under the optimum condition, the purity of aragonite in products was determined to be more than 99.4 (w/w) %, by XRD and FTIR analyses. The specific surface area was obtained to be 5-8 m2 g-1 by the BET method, and the morphology was characterized in wisker with several micrometers in length by SEM.

    DOI CiNii

  • 廃ホタテ貝殻焼成物を原料としたアラゴナイト型軽質炭酸カルシウムの合成における種結晶の影響

    笹木 圭子, 本郷 大, 恒川 昌美

    資源・素材   1997 ( 3 ) 157 - 157  1997年09月

    CiNii

  • 植物系廃資源を利用した黄鉄鉱の溶解抑制とそのメカニズム-鉱山における酸性環境の修復のための提言-

    笹木 圭子, 恒川 昌美

    資源・素材   1997 ( 3 ) 5 - 8  1997年09月

    CiNii

  • Confirmation of a sulfur-rich layer on pyrite after oxidative dissolution by Fe(III) ions around pH 2 - Reply

    K Sasaki, M Tsunekawa, T Ohtsuka, H Konno

    GEOCHIMICA ET COSMOCHIMICA ACTA   61 ( 15 ) 3273 - 3274  1997年08月

    その他  

  • Raman study of the microbially mediated dissolution of pyrite by Thiobacillus ferrooxidans

    K Sasaki

    CANADIAN MINERALOGIST   35   999 - 1008  1997年08月

     概要を見る

    Raman spectroscopy was applied to the microbially mediated dissolution of pyrite by high density (more than 10(9) cells) of Thiobacillus ferrooxidans. In the range 600-200 cm(-1), peaks corresponding to secondary minerals such as elemental sulfur and jarosite were observed in addition to those of pyrite. Small amounts of elemental sulfur and poorly crystalline jarosite were detected by Raman spectroscopy, but are undetectable by X-ray diffraction and Fourier transform infrared spectroscopy. Ammoniojarosite was predominantly formed in microbially mediated dissolution of pyrite with a high density of cells, whereas jarosite was formed in the sterilized control. This finding is probably ultimately due to the much greater amount of jarosite precursors (Fe3+ sulfate complexes) formed by the bacterial oxidation of iron. Initially, and in both cases, the kinetically favored jarosite appeared, but in the presence of bacteria, there was so much precursor present that the available potassium was exhausted. Ammoniojarosite subsequently was formed. In the sterilized control, precursors were less readily formed, and jarosite formed. There was no evidence for direct involvement of bacteria in the formation of jarosite. The changes in mineral compositions are correlated with those in the solutions. Raman spectroscopy was used to follow compositional changes in minerals during the microbially mediated dissolution of pyrite.

  • Thiobacillus ferrooxidansの介在により生成したジャロサイト群の形態的特徴

    笹木 圭子

    鉱物学雜誌 = Journal of the Mineralogical Society of Japan   26 ( 2 ) 47 - 50  1997年05月

    CiNii

  • Thiobacillus ferrooxidansによる黄鉄鉱の溶解にともなうラマンスペクトルの変化

    笹木圭子, 恒川昌美, 棚池修, 金野英隆

    分析化学討論会講演要旨集   58th   112  1997年

    J-GLOBAL

  • Suppression of microbially mediated dissolution of pyrite by originally isolated fulvic acids and related compounds

    K Sasaki, M Tsunekawa, S Tanaka, H Konno

    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS   119 ( 2-3 ) 241 - 253  1996年12月

     概要を見る

    Originally isolated fulvic acids (FA) were applied to the suppression of microbially mediated dissolution of pyrite by Thiobacillus ferrooxidans and Thiobacillus thiooxidans, and compared with tannic acids (TA) and oxalic acid (OA). The mechanism of suppression was studied using X-ray photoelectron spectrometry, Fourier transformed infrared spectroscopy, and solution analysis.
    Preliminary experiments showed that the reaction rate of Fe(III) with pyrite was faster than the rate of reduction of Fe(III) to Fe(II) by FA, and that FA adsorbed to the pyrite surface and moderately suppressed dissolution of the pyrite.
    Release of S and Fe species and decreases in pH in the microbially mediated dissolution of pyrite were effectively suppressed in the presence of more than 10 ppm of TA: 200 ppm of FA, and 250 ppm of OA. The suppression was considered to be due to the inhibition of microorganisms by organic acids and their adsorption to the active sites of pyrite surfaces in addition to reduction and complexation of Fe(III) ions by these acids. The results indicate that humic substances are useful for remediation in mine environments.

    DOI

  • Thiobacillus ferrooxidans および Thiobacillus thiooxidansの細胞増殖と鉄・硫黄酸化に対する阻害剤としてのタンニン酸およびフルボ酸の評価

    笹木 圭子, 恒川 昌美

    資源と素材 : 資源・素材学会誌 : journal of the Mining and Materials Processing Institute of Japan   112 ( 13 ) 929 - 933  1996年11月

    CiNii

  • Mineral Bioprocessingへの挑戦〜北大・鉱物処理工学研究室における最近の研究〜

    伊藤 真由美, 恒川 昌美, 平島 剛, 広吉 直樹, 笹木 圭子

    資源・素材   1996 ( 1 ) 67 - 67  1996年10月

    CiNii

  • 好気的環境下における微生物を媒介とした黄鉄鉱溶解の天然有機物による抑制

    笹木 圭子, 恒川 昌美, 金野 英隆, 田中 俊逸

    一般発表(研究・業績発表)講演要旨集   1996 ( 1 ) 36 - 36  1996年03月

    CiNii

  • pH 2付近におけるFe(III)イオンによる黄鉄鉱の酸化溶解に及ぼすFe(II)イオンの影響

    笹木 佳子, 恒川 昌美, 金野 英隆

    資源と素材 : 資源・素材学会誌 : journal of the Mining and Materials Processing Institute of Japan   112 ( 1 ) 49 - 53  1996年01月

    CiNii

  • Effect of Fe((]G0002[)) Ions on Pyrite Dissolution with Fe((]G0003[)) Ions near pH 2(共著)

    Keiko SASAKI, Masami TSUNEKAWA, Hidetaka KONNO

    SHIGEN-TO-SOZAI   112 ( 4 ) 231 - 237  1996年

    DOI

  • Characterization of argentojarosite formed from biologically oxidized Fe3+ ions

    K Sasaki, M Tsunekawa, H Konno

    CANADIAN MINERALOGIST   33   1311 - 1319  1995年12月

     概要を見る

    Argentojarosite [AgFe3(SO4)(2)(OH)(6)] was synthesized without by-products at ambient temperatures from Fe3+ ions formed from Fe2+ ions by the iron-oxidizing bacteria Thiobacillus ferrooxidans. The product was characterized using X-ray-fluorescence (XRF) analysis, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse-reflectance infrared Fourier-transform spectrometry (DRIFTS), inductively coupled plasma - atomic emission spectrometry (ICP-AES) and scanning electron microscopy (SEM). We found, using XRD, DRIFTS, and chemical analysis, that argentojarosite was formed from Fe3+ ions oxidized both biologically by T. ferroxidans and chemically by H2O2. Differences were noted in the morphologies and intensities at two upsilon(3) (SO42-) bands of DRIFTS between biological and chemical products, but there is no major difference in chemical compositions, chemical species and XRD patterns. It is likely that the extracellular substances (secretions) from bacteria take part in the aggregation of the argentojarosite formed.

  • 鉄酸化細菌による黄鉄鉱の酸化溶解にともなう二次鉱物の生成

    笹木 圭子, 恒川 昌美, 金野 英隆

    資源・素材   1995   7 - 10  1995年09月

    CiNii

  • EFFECT OF ANIONIC LIGANDS ON THE REACTIVITY OF PYRITE WITH FE(III) IONS IN ACID-SOLUTIONS

    K SASAKI, M TSUNEKAWA, K HASEBE, H KONNO

    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS   101 ( 1 ) 39 - 49  1995年08月

     概要を見る

    The reactivity of pyrite with Fe(III) ions in solutions of pH around 2 containing anionic species was evaluated by the determination of released Fe(II) ions, and by surface analysis of pyrite using X-ray photoelectron spectroscopy (XPS). The release of Fe(II) ions decreased with increasing concentration of total anionic species, and the suppression of pyrite dissolution was in the order chloride &lt; sulfate &lt;&lt;&lt;phosphate approximate to oxalate. The Fe(III)-CDTA and [Fe(CN)(6)](3-) complexes did not function as oxidants. For [Fe(CN)(6)](3-), the results were explained by a mechanism based on molecular orbital theory, since the complex is inert and of low-spin type. For the others, the order of suppression was found to be in parallel with the order of potential as oxidant, the standard redox potential, E(0). The redox couples of Fe(III)-CDTA and Fe(III)-oxalate complexes have lower E(0) values and this is considered to be the reason for no oxidation. In the phosphate system, colloid formation and polynucleation of Fe(III) ions were observed and these were additional factors in the suppression. The experimental results and the calculated E(0) values indicate that E(0) for SO42-/pyrite-S may be around 0.3 V. This means that E(0) is an important measure for estimating the ligand effect.

    DOI CiNii

  • CONFIRMATION OF A SULFUR-RICH LAYER ON PYRITE AFTER OXIDATIVE DISSOLUTION BY FE(III) IONS AROUND PH-2

    K SASAKI, M TSUNEKAWA, T OHTSUKA, H KONNO

    GEOCHIMICA ET COSMOCHIMICA ACTA   59 ( 15 ) 3155 - 3158  1995年08月

     概要を見る

    The stoichiometry of pyrite dissolution by Fe(III) ions was studied in chloride media around pH 2. Pyrite was found to dissolve nonstoichiometrically during the initial tens of hours and a S-rich layer was formed on the pyrite due to preferential dissolution of iron. The major constituent of the layer was elemental S, identified by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy.

    DOI

  • 強酸性条件下における jarosite 生成に及ぼす共存一価陽イオンの影響

    笹木 圭子, 恒川 昌美, 金野 英隆

    一般発表(研究・業績発表)講演要旨集   1995 ( 1 ) 127 - 127  1995年03月

    CiNii

  • NONSTOICHIOMETRY IN THE OXIDATIVE DISSOLUTION OF PYRITE IN ACID-SOLUTIONS

    K SASAKI, M TSUNEKAWA, H KONNO

    BUNSEKI KAGAKU   43 ( 11 ) 911 - 917  1994年11月

     概要を見る

    The oxidative dissolution of pyrite, FeS2, by Fe(III) ions in hydrochloric acid solutions at around pH 2 was investigated by spectrophotometry, ICP-AES and X-ray photoelectron spectroscopy (XPS). All the experimental results showed that the preferential dissolution of iron in pyrite took place resulting in the formation of a surface layer enriched with sulfur. The preferential dissolution was enhanced by increasing the initial concentration of Fe(III) ions. Accordingly, a classical stoichiometric dissolution ([Fe]/[S] = 0.5) mechanism can not explain the present results. The dissolution rate was independent of Cl- ion concentration, but dependent on Fe(III) ion concentration. The oxidative dissolution of pyrite was suppressed by increasing the concentration of Fe(II) ions. The present results suggest that the kinetic equations should be formulated, considering both dissolved iron and sulfur species.

  • EFFECT OF GRINDING ON THE RATE OF OXIDATION OF PYRITE BY OXYGEN IN ACID-SOLUTIONS

    K SASAKI

    GEOCHIMICA ET COSMOCHIMICA ACTA   58 ( 21 ) 4649 - 4655  1994年11月

     概要を見る

    Solubility of pyrite (FeS2) ground for different periods was investigated in acid solutions in air. In the initial dissolution, up to 50 h, the dissolution rate, r, was high, due to oxidized species such as FeSO4 formed by grinding. After 50 h, the surface of pyrite was exposed and the dissolution rate decreased. The formation and dissolution of oxidized species were confirmed by X-ray photoelectron spectroscopy, XPS. From the dissolution rates of Fe and S species, r(Fe), and r(S), for 50-200 h, it was found that pyrite dissolves nonstoichiometrically (r(S)/r(Fe) &lt; 2) and that grinding promotes the dissolution of sulfur species leading to the stoichiometric dissolution (r(S)/r(Fe) = 2) The increase in us can be explained by the displacement of S atoms in the crystal due to the grinding. The effective Debye-Waller parameter, B-eff, depends on the displacement of constituent atoms in the crystal from their equilibrium positions and is measured from the diffraction intensities of X-rays. The parameter for S atoms in pyrite, B-eff(S), increased by one or two orders of magnitude with increasing grinding time, t(G), while that for the pyrite, B-eff(FeS2), did not change markedly. It was established that r(S) is closely related to B-eff(S). The phenomenon may be regarded as a type of mechanical activation.

    DOI CiNii

  • STRUCTURAL STRAIN IN PYRITES EVALUATED BY X-RAY-POWDER DIFFRACTION

    K SASAKI, H KONNO, M INAGAKI

    JOURNAL OF MATERIALS SCIENCE   29 ( 6 ) 1666 - 1669  1994年03月

     概要を見る

    Two parameters for measuring the structural strain, the effective Debye-Waller parameter, B-eff, and lattice strain, epsilon, were evaluated on a natural pyrite (FeS2) after grinding. The effective Debye-Waller parameter, B-eff, which depends on the displacement of atoms in the crystal, was calculated for the overall crystal, B-eff(FeS2), and for sulphur, B-eff(S), from the intensities of the X-ray diffraction lines. The B-eff(S) increased markedly with increasing grinding time, while B-eff(FeS2) did not change significantly. The lattice strain, epsilon, was not recognized. These observations suggest that the displacement of sulphur atoms preferentially takes place by grinding. The relations between these B-eff values and crystallite size, L, were observed to be common for two different methods of grinding. This tendency was considered to be an inherent property of pyrite. The value of B-eff(S) is a useful index to estimate mechanically caused strain in pyrite.

    DOI CiNii

  • Thiobacillus ferrooxidansによる黄鉄鉱の浸出挙動と鉱物表面のキャラクタリゼーション(共著)

    笹木 圭子, 恒川 昌美, 金野 英隆, 平島 剛, 高森 隆勝

    資源と素材   109 ( 1 ) 29 - 35  1993年

    DOI CiNii

  • Thiobacillus thiooxidansと共存するThiobacillus ferrooxidansの菌体数計数についての一考察--メンブランフィルタ-を用いた選択培養法によるアプロ-チ

    高森 隆勝, 笹木 圭子, 恒川 昌美, 平島 剛

    北海道大学工学部研究報告   ( 154 ) p1 - 8  1991年01月

    CiNii

  • バクテリアリーチングにおけるパイライト表面生成物のX線光電子分光分析(共著)

    金野 英隆, 笹木 圭子, 恒川 昌美, 高森 隆勝, 古市 隆三郎

    分析化学   40 ( 11 ) 609 - 616  1991年

    DOI

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  • 全学教育実験(コアセミナー科目)

    九州大学  

    2005年
    -
     
     

  • 地球環境工学入門I

    九州大学  

    2005年
    -
     
     

  • 地球環境工学卒業研究

    九州大学  

    2005年
    -
     
     

  • 資源システム工学実験第二

    九州大学  

    2005年
    -
     
     

  • 資源処理工学第二

    九州大学  

    2005年
    -
     
     

  • 資源処理工学第二特論

    九州大学  

    2005年
    -
     
     

  • 地球システム工学インターンシップ

    九州大学  

    2005年
    -
     
     

  • 全学教育実験(コアセミナー科目)

    九州大学  

    2004年
    -
     
     

  • 地球システム工学インターンシップ

    九州大学  

    2004年
    -
     
     

  • 地球環境工学卒業研究

    九州大学  

    2004年
    -
     
     

  • 地球環境工学入門I

    九州大学  

    2004年
    -
     
     

  • 資源システム工学実験第二

    九州大学  

    2004年
    -
     
     

  • 資源処理工学第二

    九州大学  

    2004年
    -
     
     

  • 地球学 特別講義

    金沢大学  

  • 環境修復工学

    九州大学  

  • 地球環境化学

    九州大学  

▼全件表示

 

社会貢献活動

  • 超難処理金鉱石の バイオハイドロメタラジー

    東北大学多元物質化学研究所  第19回東北大学多元研研究発表会 

    2019年12月
     
     

  • Challenges to gold recovery from carbonaceous gold ores using biotechnology

    International Conference on Asian Pacific Mining and Mietallurgy 2019 

    2019年11月
     
     

  • バイオテクノロジーによる 難処理金鉱石からの金回収率の向上

    日本技術士会 

    2019年10月
     
     

  • 酵素反応をとりいれたグラファイト質 難処理金鉱石のミネラルプロセッシング

    日本粉体工学討論会 

    2019年10月
     
     

学術貢献活動

  • 日本学術会議 会員

    その他

    2023年10月
    -
    2026年09月
  • 資源・素材学会 会長

    2023年03月
    -
    2024年02月

他学部・他研究科等兼任情報

  • 理工学術院   大学院創造理工学研究科

学内研究所・附属機関兼任歴

  • 2024年
     
     

    理工学術院総合研究所   兼任研究員