A previously proposed method for estimating antisolvent crystallization kinetics has been successfully applied to cooling crystallization to yield kinetic parameters for simulating the crystallization process. In particular, the primary nucleation kinetics were analyzed using the modified induction time data, essentially as proposed by Kubota. The number density at the detection point, (N/M)det, is an important value in the kinetic analysis but is difficult to estimate experimentally. Therefore, the numerical optimization was used to estimate the value of (N/M)det in the same manner as for antisolvent crystallization. Primary nucleation was detected for both antisolvent and cooling crystallization with a sensitive detection method, visual detection, to reduce the effects of secondary nucleation. As a result, the (N/M)det values for each method are small and almost identical (approximately 200 #/kg-solvent). The secondary nucleation and growth rate parameters for cooling crystallization were also successfully determined by numerical optimization. All the kinetic parameters determined for cooling crystallization were evaluated with experimental data. Consequently, it is confirmed that these rate parameters can simulate trends in concentration as well as the final number mean diameter of the product crystals with acceptable accuracy. Moreover, the crystallization rate parameters determined for both antisolvent and cooling crystallization were validated with simulations and experimental data from combined crystallization, where antisolvent crystallization is followed by cooling crystallization. The simulation and experimental results for the concentration trend and number mean diameter of the produced crystal were in good agreement. The applicability of our estimation method to both antisolvent and cooling crystallization indicates the broad utility of this method for various crystallization process in the pharmaceutical industry.

Anti-encrustation additives were mainly investigated in nitric acid solution with zirconium (Zr), molybdenum (Mo), and tellurium (Te) to prevent the encrustation of zirconium molybdate hydrate (ZMH). The ZMH generated by reaction crystallization of Mo and Zr as main fission products has a high adhesion property in spent nuclear fuel reprocessing. In addition, it is reported that Te, which is also one of the fission products, precipitates together with ZMH. Encrustation of precipitates containing Te was effectively prevented by adding molybdenum trioxide (MoO3) crystals as an anti-encrustation reagent. The encrustation amount was found to be larger than that under the condition of only Zr and Mo without Te. Consequently, it was suggested that the high adhesion property of Te affected the encrustation amount of ZMH.

Gout is arthritis induced by monosodium urate monohydrate (MSU) crystals. The treatment of gout is mainly a symptomatic treatment, by suppressing the blood uric acid concentration with drugs. Here, the changes in crystal morphology in the process of MSU crystallization were investigated. Experiments were conducted to clarify the mechanisms of nucleation and growth of the MSU crystals, revealing that MSU first precipitated as granular crystals. Thereafter, nucleation and growth of needle-like crystals were observed concomitant with the disappearance of the granular crystals. These results suggest that it is necessary to suppress the nucleation of granular crystals and the change in morphology from granular to needle-like of the MSU crystals that cause gout.

Most of the amino acids that are utilized as medical raw materials and food additives show polymorphism. To improve the functionality of amino acid crystals, an effective method of polymorph control is required in the crystallization process. Here, primary nucleation of L-arginine hydrochloride by ultrasonication was investigated. L-Arginine hydrochloride exhibits polymorphism, and it crystallizes into three distinct crystal forms. A cooling crystallization experiment was performed, and nucleation of each polymorph upon ultrasonication was observed. In addition, the nucleation was analyzed using the nucleation probability theory. The results indicate that ultrasonic irradiation would significantly induce the nucleation of a particular polymorph.

Partial seeding, in which the nuclei originating from seed crystals grow to yield the product crystals, was simulated and optimized for controlling the batch cooling crystallization process of L-arginine. The product quality was evaluated by the coefficient of variation (CV) of the crystal size distribution. First, the optimum seed amount for partial seeding was estimated by simulation. Then, the simulated values of the optimum seed amount and the resulting local minimum CV were correlated with the seed crystal size and the cooling rate. The correlation can be utilized for estimating the seed amount in the case that the seed crystals are added in a slurry. Finally, these simulated values were compared to the measured ones. Consequently, the optimum seed amount was suggested to be reasonably predicted.

The kinetic parameters of stochastic primary nucleation were estimated for the batch-cooling crystallization of L-arginine. It is difficult for process analytical tools to detect the first nucleus. In this study, the latent period for the total number of crystals to be increased to a predetermined threshold was repeatedly measured with focused-beam reflectance measurements. Consequently, the latent periods were different in each measurement due to the stochastic behavior of both primary and secondary nucleation. Therefore, at first, the distribution of the latent periods was estimated by a Monte Carlo simulation for some combinations of the kinetic parameters of primary nucleation. In the simulation, stochastic integrals of the population and mass balance equations were solved. Then, the parameters of the distribution of latent periods were estimated and correlated with the kinetic parameters of primary nucleation. The resulting correlation was represented by a mapping. Finally, the parameters of the actual distribution were input into the inverse mapping, and the kinetic parameters were estimated as the outputs. The estimated kinetic parameters were validated using statistical techniques, which implied that the observed distribution function of the latent periods for the thresholds used in the estimation coincided reasonably with the simulated one based on the estimated parameters.

潜熱蓄熱材として利用が期待される酢酸カリウム2水塩の融点T_m=291 Kと潜熱量ΔH_f=135 kJ/kgとの関係の必然性を明らかにするため，その化学構造式に着目し，両者の関係について定量的検討を試みた．まず，同一の陰イオンを有し陽イオンがNa⁺とK⁺である化合物同士で，水和塩の結晶水の数とその脱水転移温度とが明らかな組合せ4組を検討した．その結果，総じてその脱水転移温度はナトリウム塩に対しカリウム塩の方が20–50 K程度低くなることがわかった．また，結晶中のイオン半径に対する水溶液中のストークス半径の比が小さいほど，脱水転移温度，いわゆるT_mが低くなる傾向を指摘した．次に，水和塩が融解するときのエントロピー変化量ΔS_f（=ΔH_f/T_m）を水単体の融解エントロピー変化量ΔS_f,HOと水和塩中の結晶水の重量分率Φ_wとで関係づけ，これに基づきT_mとΔH_fとの関係を記述する簡便な関係式を導出した．この式を実測値（水和塩計18種）を用いて検証した結果，水和塩の化学構造式とそのT_m値が決定されれば，±0.212の相対標準偏差でΔH_f値を推算できることを明らかにした．またこれにより，酢酸カリウム2水塩のT_mに対するΔH_fの数値の必然性が確認された．

水和塩系の化合物は単位体積当たりの蓄熱密度が高いことから，潜熱蓄熱材として期待されている．しかし，冷房空調用に適した温度範囲273–303 Kに融点を有するものは少なく，選択の範囲が限られていた．このため，新たな潜熱蓄熱材候補となりうる水和塩の探査を目的として，本研究では酢酸カリウムの水和物について温度と水和数との関係を検討し，潜熱蓄熱材としての可能性を調べた．まず，酢酸カリウム水溶液の直接観察の結果，一般に知られる0.5および1.5水塩の晶析特性を確認した．また，冷却温度を229 Kまで低下することによって酢酸カリウム2水塩が晶析することが示唆された．晶析した2水塩の融点は291 Kで，潜熱量は135 kJ/kgであった．この潜熱量の数値は，水和塩系で285–294 Kの範囲内に融点を有する他の冷房空調用途の候補素材6種のうちのほぼ中間的な位置にあり，それらと遜色がないことがわかった．

Methodologies for the estimation of nucleation rate parameters, which are rate constants and orders in antisolvent crystallization, are proposed with the aim of applying to the pharmaceutical industry. Primary and secondary nucleations are clearly distinguished and these rates are defined as power laws of the supersaturation in our antisolvent crystallization model. Primary nucleation rate parameters were experimentally determined using the theoretical equation about the modified induction time in antisolvent crystallization based on the past study reported by Kubota, N. [ J. Cryst. Growth 2010, 312, 548-554 ], in which the induction time is defined as the time when the number density of the crystal reaches a fixed value. It is difficult to estimate the number density at the detection point using an experimental approach. Therefore, a numerical approach was used to determine the number density. The estimated number density at the detection point can determine the secondary nucleation rate parameters. These determined nucleation rate parameters become effective factors for simulating the number mean diameter in antisolvent crystallization and can be applied to the pharmaceutical industry.

With the aim of simulating the product crystal size, which is one of the important physical properties for active pharmaceutical ingredients, an antisolvent crystallization model is proposed, including only six experimentally determined kinetic parameters to develop a concise model. As a first step, the methodology to assess the growth rate parameters, which are some of the six kinetic parameters, is discussed. An approach for appropriately treating the size distribution data obtained by means of the laser diffraction/scattering method is suggested. The determined growth rate parameters could be used to simulate the crystal size indicating that the simulation by crystallization modeling is a practical application for the pharmaceutical industry.

Numerical simulation of the seeded batch cooling crystallization process of active pharmaceutical ingredients was performed. Crystal size distribution was observed by focused-beam reflectance measurements and concentration by simultaneous Fourier transform infrared spectroscopy. First, kinetic parameters were estimated. Nucleation rate coefficient and order were estimated from the linear regression equation between cooling rate and metastable zone width. The remaining parameters were estimated from the evaluation function. Then, the numerical simulation was performed by utilizing the method of moments. Finally, observed data were compared with simulated data. The simulated values of mean mass size corresponded reasonably with the observed ones.

Simulations were performed for seeded batch cooling crystallization. In industry, partial seeding is often utilized, where a small amount of seed crystal is added to trigger secondary nucleation and grown secondary nuclei are obtained as the product. Partial seeding was investigated by computer simulation in this study. First, the coefficient of variation (CV) of the product crystal size distribution (CSD) was proven to take two local minima, one in the partial seeding range and the other in the range in which the product was mainly composed of seed-grown crystals. The local minimum point in the partial seeding range was considered as an optimum condition for partial seeding. Then, CSDs of grown seed crystals and nuclei were simulated at the optimum seed-loading ratio. As a result, the product was found to be composed mainly of grown secondary nuclei induced by grown seed crystals and grown secondary nuclei themselves. Partial seeding performed at the optimum seed-loading ratio yielded a reasonably good product of unimodal size distribution. Finally, the optimum seed-loading ratio was correlated with the cooling rate and seed crystal size and was found to depend on the cooling rate and more strongly on the seed crystal size. As the cooling rate was decreased, the minimum CV was shown to decrease and the mean size at the optimum seed-loading ratio was shown to increase.

The dispersion of batch time, i.e., the time for finalizing batch crystallization satisfying batch end conditions, in internally seeded cooling crystallization with direct nucleation control (DNC) was estimated by computer simulation. The batch time is considered to disperse at such crystallization due to stochastic nucleation. In this study, first, a population balance equation was digitized for numerical calculation, and the simulation was developed in MATLAB. Then, repetitive simulations of internally seeded cooling crystallization considering stochastic nucleation with DNC were performed. Finally, the batch time of each simulation was arranged. As a result, it was found that there is little batch time dispersion in crystallization controlled by DNC and without adding seed.

High-quality single crystals are necessary for structural analysis of proteins. However, it is difficult to obtain high-quality single crystals in a short time. Therefore, a membrane crystallization method was applied in which lysozyme is concentrated on the membrane surface using an ultrafiltration membrane. Membrane surface concentrations, which cannot be measured, were calculated based on the measurable permeation flux. At all operating pressures, the measured and simulated permeation fluxes were in close agreement, allowing the membrane surface concentration to be estimated. The membrane surface concentration increased rapidly at all pressures during the initial pressurization, indicating that crystals were formed at an early stage.

Generally, supercooling as large as about 25 K is necessary to form tetrahydrofuran clathrate hydrate (THF hydrate). In the present study, we have investigated how the existence of various additives affects the degree of supercooling (ΔT) in the THF hydrate formation without any external stimulus. The addition of either AgO or Ag3PO4 yields the best ΔT suppression, where ΔT was approximately 4 K, much smaller than 25 K. Raman spectra reveal that, in the supercooled THF aqueous solution with AgO before crystallization, the THF molecule forms a coordination bond with AgO, whereas it forms a hydrogen bond with a water molecule in the system without AgO. The oxygen atom of the THF molecules, which is a hydrogen-bonding site, was oriented to a AgO molecule in the aqueous solution. The orientation and the subsequent interruption of the hydrogen bond make it easy to form a hydration shell around the THF molecule. Scanning Transmission Electron Microscopy images by using the freeze-fracture replica method reveal that a cluster, which is the smallest structural unit of a crystal, includes Ag-containing nanoparticles formed from AgO or Ag3PO4, which accelerate the cluster formation. As a result, the addition of AgO or Ag3PO4 effectively diminishes the degree of supercooling in the THF hydrate formation.

潜熱蓄熱材として利用が期待される炭酸ナトリウム10水塩（融点T_m,0=304.5 K, 潜熱量ΔH_f,0=153 kJ/kg, ともに実測値）および炭酸ナトリウム10水塩0.6 mol/molとリン酸水素二ナトリウム12水塩0.4 mol/molとの水和塩共晶（E（P–C）；融点T_m,0=298 K, 潜熱量ΔH_f,0=213 kJ/kg, ともに実測値）の2種水和塩系に対し，その融液に溶解可能な添加物を混合した系について，融点T_mおよび潜熱量ΔH_fの変化を測定した．簡易的な実験式を用い，各添加物の融点降下能力a_meおよび潜熱量低下能力b_meを数値化した．これら能力の数値は添加物ごとに異なったが，能力比率b_me/a_meは添加物の種類によらずほぼ同じ数値となって，水和塩系それぞれの固有値を示した．さらに，前報（Watanabe, 2017）およびその続報（Watanabe and Hirasawa, 2018b）で得られた塩化カルシウム6水塩系およびリン酸水素二ナトリウム12水塩系の各b_me/a_me値もあわせて比較検討した結果，水和塩単体のT_m,0およびΔH_f,0でそれぞれ規格化した相対融点降下度［1−（T_m/T_m,0）］と相対潜熱量低下度［1−（ΔH_f/ΔH_f,0）］との間には，水和塩系の種類に依存しない下式で表されるほぼ一定の数値関係が成立することがわかった．

<img align="middle" src="./Graphics/abst-math31.png"/>

融点降下法による潜熱蓄熱材の適用温度範囲の拡大をねらい，特に医療用保温材などに利用されるリン酸水素二ナトリウム12水塩（融点T_m,0=308.5 K, 潜熱量ΔH_f,0=227 kJ/kg, ともに実測値）の融液に溶解可能な添加物5種（リン酸三カリウム，リン酸水素二カリウム，リン酸二水素カリウム，リン酸二水素アンモニウムおよびリン酸二水素ナトリウム2水塩）を混合した系について，融点T_mおよび潜熱量ΔH_fの変化を測定した．さらに前報（Watanabe and Hirasawa, 2017; Watanabe, 2017）で提案した，添加物濃度と融点降下度および潜熱量低下度との関係を記述する簡易的な実験式を用い，各添加物の融点降下能力および潜熱量低下能力を数値化した．これら能力の数値は添加物ごとに異なり，それぞれ固有値を示した．これに対し，融点降下度と潜熱量低下度との間には，添加物の種類に依存しない下式で表されるほぼ一定の数値関係が成立することがわかった．

<img align="middle" src="./Graphics/abst-math1.png"/>

Most of the amino acids that are utilized as medical raw materials and food additives show polymorphism. To improve the physical and chemical properties of the crystals, an effective method for polymorph control is required in the crystallization process. In this study, polymorph control of L-phenylalanine in cooling crystallization by ultrasonication was investigated. L-Phenylalanine crystallizes in anhydrate and monohydrate forms. Without ultrasonication, a mixture of monohydrate and anhydrate forms was obtained. In contrast, the yield of monohydrate was increased by ultrasonication. In addition, ultrasonication shortened the induction time. It was considered that ultrasonic energy could supply the energy required for primary nucleation.

Chord length distribution (CLD) can be determined by an in-line measuring system with focused-beam reflectance measurement, but it can differ from crystal size distribution (CSD). However, expected values of CLD can be calculated from CSD by statistical methods and vice versa. In this study, a correlation equation between crystal size and aspect ratio during cooling crystallization was obtained and a mapping matrix was calculated based on the correlation equation. Then, the suspension obtained in cooling crystallization was sampled and CSDs were measured by microscopy at the same time that CLDs were measured with FBRM. As a result of error evaluation, transformation of CLD into CSD reduced the errors between CLDs and CSDs except in the early stage of crystallization.

In nuclear fuel reprocessing, spent nuclear fuel is dissolved by a nitric acid. It is now known that molybdenum and zirconium in fission products react to form zirconium molybdate hydrate (ZMH). ZMH adheres to the inner surface of reprocessing equipment, which affects the extraction efficiency in the subsequent extraction process. Therefore, a new prevention method of ZMH encrustation is required for stable plant operation. In this study, the encrustation amount of ZMH was investigated. Observing the deposition process, it was clarified that ZMH fine crystals were generated and agglomerated, followed by the rapid deposition. The encrustation amount of ZMH decreased as temperature or initial Mo/Zr mole ratio increased, or as the concentration of a nitric acid was reduced.

共晶法は，潜熱蓄熱材の融点を調整してその適用温度範囲を広げる有効な手法の一つである．ともに水和塩系蓄熱材である炭酸ナトリウム10水塩とリン酸水素二ナトリウム12水塩との混合によって生成する共晶の組成を明らかにするため，両水和塩混合系の擬二成分相図を作成した．加熱曲線によって決定された各混合組成における融点の分布から，相図は単純共晶型で，共晶の融点は298 Kであった．共晶組成を特定する手法として，融点降下の実験式を利用する方法と融解潜熱量の変化を利用する方法とをそれぞれ試みた．その結果，前者の手法ではリン酸水素二ナトリウム12水塩の混合モル分率として共晶組成が0.40 mol/mol, また後者では0.37–0.38 mol/molと見積もられた．この数値は，Watanabe and Hirasawa（2018）による混合水和塩の融液中における解離イオンの等価的交換によって共晶が形成するとする仮説から計算される数値0.4 mol/molとよく一致した．

A large degree of supercooling is necessary to form the tetra-n-butyl ammonium bromide (TBAB) semiclathrate hydrate. One of the effective methods to suppress supercooling is the utilization of a kind of hysteresis called the "memory effect". Generally, the memory effect reduces supercooling and/or the induction period in clathrate hydrate formation. In the present study, we have observed the solution structure of TBAB aqueous solutions in the formation and decomposition processes of TBAB semiclathrate hydrate by scanning electron microscopy (SEM) with the freeze-fracture replica method. The relationship between the memory effect and the solution structures of the TBAB supercooled aqueous solution was elucidated. The memory effect in the TBAB semiclathrate hydrate reformation is derived from the existence of residual clusters of 10-20 nm in the TBAB aqueous solution at 286.2 K, which is 1.0 K higher than the equilibrium decomposition temperature, even after the TBAB semiclathrate hydrate was completely decomposed.

共晶法は，潜熱蓄熱材の融点を調整してその適用温度範囲を広げる有効な手法の一つである．水和塩混合系における共晶組成の必然性を明らかにするため，硝酸ニッケル6水塩–塩化コバルト6水塩ならびに塩化ニッケル6水塩–硝酸コバルト6水塩の二成分混合系2種について擬二成分相図を作成した．加熱曲線から決定された各水和塩の融点は，それぞれ順に53.5, 53, 51.5そして53.5°Cであった．また両相図とも単純共晶型で，等モル混合で生成した共晶の融点は共に同じ30°Cであった．混合系の結晶組成は混合比率に対応して変化したが，混合前の当初6水塩には帰属されない新たな結晶相も晶析し，その比率は共晶組成において最大となった．生成した各共晶の粉末X線回折パターンは一致しており，両者は同一結晶組成にあることがわかった．解離イオンの等価的交換による共晶形成機構が提案された．また，すべての解離イオンに対して対イオンが相互に等価的数量関係を維持し得る混合比率が，共晶組成であることが示唆された．

本研究では，エリスリトールの過冷却特性に対する塩添加の影響について検討を行うことにより，高い蓄熱密度を有し，かつ，室温環境下においても過冷却を保持し得る新規な糖アルコール系の潜熱蓄熱材を創出し，その過冷却保持のメカニズムを明らかにした．具体的には，エリスリトールの添加剤として，カチオン種，アニオン種とその価数の異なる塩について，各々の添加量をパラメータに，結晶化開始温度，過冷却保持時間の評価を行うとともに，エリスリトールと添加剤との相互作用に着目して，核磁気共鳴（NMR）装置を用いて過冷却保持のメカニズム検討を行った．その結果，エリスリトールの添加剤として，1価のアニオンを含む塩は，過冷却保持，2価のアニオンを含む塩は，過冷却抑制に有効であり，カチオン種の影響は，アニオン種と比較して小さいことが明らかとなった．また，室温環境下において，エリスリトールの過冷却を保持するための添加剤として，アニオンとして酢酸イオンを含む塩を抽出し，結晶化開始温度の低下，および過冷却保持の長時間化は，エリスリトールのヒドロキシ基と酢酸イオンの相互作用に起因すると推察した．

We have observed the solution structure of the supercooled sodium acetate aqueous solution, especially for the existence of clusters and their crystallization process, by means of Scanning electron microscopy (SEM) with the freeze replica method. Microscopic internal structure of sodium acetate trihydrate crystals mainly constitutes the aggregates of 100-200 nm in diameter, which consists of the clusters of 10-20 nm in diameter. In the case of a supercooled aqueous solution of 293 K, two types of aspect in the vitrified aqueous solution mainly exist: one is the clusters of 10-20 nm in diameter; the other is the smooth zone without any structure. At 263 K, the relationship among clusters of 10-20 nm and their aggregates of 100-200 nm was clearly observed. The aggregates construct the three-dimensional loose networks, which are not fully packed, different from the crystal. (C) 2017 Elsevier B.V. All rights reserved.

The solubility of aluminum sulfate in sulfuric aqueous solution was determined and analyzed thermodynamically. Aluminum sulfate dissolved in sulfuric acid aqueous solution not spontaneously, because the dissolution enthalpy is a positive value. The solubility of aluminum sulfate had a temperature dependency and hardly dissolved with higher concentration of sulfuric acid. On the other hand, aluminum sulfate solubility did not depend on the existence of oxalic acid, which was dissolved to saturation concentration as an additive. Moreover, the solubility curves of aluminum sulfate and oxalic acid were different in the range between 1.5 M and 6 M sulfuric acid aqueous solution at 25 degrees C. Therefore, using the difference of solubility characteristics, aluminum sulfate could be recovered selectively from waste acid containing oxalic acid. An aluminum sulfate crystal generated from the model waste acid, which was 3.5 M sulfuric acid aqueous solution containing 20 g.L-1 oxalic acid, was determined as one of aluminum sulfate hydrate by powder-XRD and its purity was 94%.

Recently, hollow sodium chloride crystals have been proposed as potential high-value-added crystals. The crystal growth mechanism of such crystals is elucidated using X-ray diffraction (XRD), optical microscopic imaging, and analysis of both the chloride ions and water content in the mixed solvent of cyclohexane and acetone. A series of experimental conditions, including the stirring time after injecting the aqueous sodium chloride solutions into the mixed solvent and the ratio of cyclohexane and acetone, are evaluated in detail. Based on experimental data, possible growth mechanisms are proposed to explain the formation of hollow sodium chloride crystals.

Amino acids are utilized as medical raw materials and food additives. It is well-known that most of the amino acids show polymorphism. Differences in the crystal structures affect the physical and chemical properties. Therefore, an effective method for polymorph control is required in the crystallization process. Polymorph control of L-arginine hydrochloride (L-ArgHCl) on antisolvent crystallization was achieved by ultrasonic irradiation. L-ArgHCl exhibits polymorphism and crystallizes into three distinct crystal forms. Without irradiation, the metastable form was selectively crystallized. In contrast, the unstable form was selectively crystallized by irradiation. Irradiation after the addition of an antisolvent led to a shorter induction time.

Deposition of needle-shaped monosodium urate monohydrate (MSU) crystals in synovial fluid provokes the acute inflammatory response of gout. The mechanism of MSU crystallization was investigated in batch operation under the same pH and Na+ concentration of synovial fluid. It was found that stirring enhanced the aggregation of needle-shaped MSU, and the deposition of MSU was faster and larger in amount. MSU crystals in supersaturated urate solution were detected by dynamic light scattering and UV absorption, suggesting that the urate concentration affected not the crystal growth but nucleation. Since the increase of the number of MSU crystals is assumed to cause a high risk of gout, this result supports the importance of the control of serum urate level as a treatment of gout.

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Sub-10-nm-sized Pt nanoparticles were synthesized by reducing Pt ions with NaBH 4 , with the addition of polyethyleneimine (PEI) as a protective reagent. Well-dispersed Pt nanoparticles with a narrow size distribution were successfully produced. When lowering the pH of the PEI solution, cubic and tetrahedral nanoparticles were observed, while at a higher pH, only spherical nanoparticles were produced. In addition, by selecting a suitable concentration of PEI, the protective reagent itself can reduce Pt ions to generate Pt nanoparticles with diameters in the range of 12.9–70.7 nm. This shows the potential of one-pot synthesis of Pt nanoparticles by just adding Pt ions and PEI.

Three polymorphs of L-Citrulline crystals, anhydrate (Form alpha, gamma and delta) and pseudo polymorph (dihydrate), were confirmed. In this study, polymorphic control of L-Citrulline was attempted by changing the ethanol concentration in ethanol-water binary solvents. First, each polymorph of L-Citrulline crystals was added to the prepared ethanol-water binary solvents and samples which were obtained chronologically were measured by XRD. Also, the crystal sizes and shapes in transformation were observed by microscope. Then, polymorphs of the crystals after transformation were determined by XRD pattern. As a result, the transformation from dihydrate to anhydrate was observed by adding dihydrate crystals to the ethanol-water binary solvent. Similarly, the transformation from anhydrate to another anhydrate was observed. Especially in the case of adding dihydrate, the existences of all polymorphs were confirmed by adjusting ethanol-water binary solvent. According to the results, it was revealed that polymorphic transformation was affected by the trace amount of water contained in ethanol-water binary solvent. Moreover, transformation from dihydrate to anhydrate was constructed with three phases, dissolution of dihydrate, nucleation and growth of anhydrate. Therefore, the solution-mediated polymorphic transformation was supposed to be a key mechanism for this transformation.

Au NPs are expected to become useful functional particles, as particle gun used for plant gene transfer and also catalysts. We have studied PSD (particle size distribution) control of Au NPs by reduction crystallization. Previous study found out importance of seeds policy and also feeding profile. In this paper, effect of pH in the reduction crystallization was investigated to clarify the possibility of Au NPs PSD control by pH operation and also their growth process. Au NPs of size range 10-600 nm were obtained in single-jet system using ascorbic acid (AsA) as a reducing agent with adjusting pH of MA. Au NPs are found to grow in the process of nucleation, agglomeration, agglomeration growth and surface growth. Au NPs tend to grow by agglomeration and become larger size in lower pH regions, and to grow only by surface growth and become smaller size in higher pH regions. (C) 2016 Elsevier B.V. All rights reserved.

The purpose of this study is particle size distribution (PSD) control of submicron sized Pt particles used for particle gun. In this report, simple reaction crystallization is conducted by mixing H2PtCl6 and ascorbic acid. Without the additive, obtained Pt particles have broad PSD and reproducibility of experiment is low. With seeding, Pt particles have narrow PSD and reproducibility improved. Additionally, mean particle diameter of 100-700 nm is controlled by changing seeding amount. Obtained particles are successfully characterized as Pt by XRD results. Moreover, XRD spectra indicate that obtained particles are polycrystals. These experimental results suggest that seeding consumed nucleation, as most nuclei attached on the seed surface. This mechanism virtually restricted nucleation to have narrow PSD can be obtained. (C) 2016 Elsevier B.V. All rights reserved.

<p>本研究は，潜熱蓄熱材として利用される塩化カルシウム6水塩（融点302 K, 実測値）の融点調整手法に関するものである．塩化カルシウム6水塩融液に溶解可能な物質を添加すると，融液の融点はその添加量に応じて降下するので，潜熱蓄熱材としての適用可能な温度範囲を広げることが期待される．しかし，この融点降下度は添加物の種類によって異なり，一般に知られる希薄な電解質水溶液系における融点降下に関する理論式からでは予測ができない．そこで，本報では添加物の融点降下能力を定量的に評価するための実験式の導出を試みた．塩化カルシウム6水塩融液に溶解する添加物9種について，それぞれの添加量に対する融点の変化を実測し，添加物の融点降下能力を簡易的な実験式を用いて数値化した．さらに，この融点降下能力が融液中で完全解離した添加物イオンによる相乗的な作用と仮定して，各解離イオンの融点降下能力を定量化し，これらの数値を用いて融点降下度を算出する簡易的な方法を提案した．</p>

With a view to controlling the melting point and extending the temperature range for practical application of calcium chloride hexahydrate as a latent heat storage material, an attempt was made to derive an empirical equation by which to evaluate quantitatively the degree to which various additives depress its melting point (measured value, 302 K). The change in melting point relative to the amount of additive was measured for each of nine additives, and the ability of each additive to depress melting point was expressed numerically by use of a simple empirical equation. Based on the assumption that the depression of melting point results from the synergistic action of completely dissociated ions in the melt, the ability of each type of ion was quantified, and the values were employed in a simple method to calculate the degree of melting point depression.

Uranium crystallization system has been developed to establish an advanced aqueous reprocessing for fast breeder reactor (FBR) fuel cycle. In the crystallization system, most part of uranium in dissolved solution of spent FBR-MOX fuels is separated as uranyl nitrate hexahydrate (UNH) crystals by a cooling operation. The targets of U yield and decontamination factor (DF) on the crystallization system are decided from FBR cycle performance and plutonium enrichment management. The DF is lowered by involving liquid and solid impurities on and in the UNH crystals during crystallization. In order to achieve the DF performance (more than 100), we discuss the purification technology of UNH crystals using a Kureha Crystal Purifier (KCP). Results show that more than 90% of uranium in the feed crystals could be recovered as the purified crystals in all test conditions, and the DFs of solid and liquid impurities on the purified UNH crystals are more than 100 under longer residence time of crystals in the column of KCP device. The purification mechanism is mainly due to the repetition of sweating and recrystallization in the column under controlled temperature.

Gold nanoparticles were precipitated on the surface of silica gel without mechanical mixing. Polyethylenimine (PEI) which was coated on the surface of silica gel reduced raw materials of hydrogen tetrachloroaurate (III) tetrahydrate (HAuCl4 center dot 4H(2)O). Formation of gold nanoparticles on silica gel was confirmed by using Field Emission Scanning Electron Microscope (FE-SEM) and Energy Dispersive X-ray Fluorescence Spectrometer (EDX). In this study, particles size distribution and coverage ratio of gold on silica gel were investigated.

Gold nanoparticles were precipitated on the surface of silica gel without mechanical mixing. Polyethylenimine (PEI) which was coated on the surface of silica gel reduced raw materials of hydrogen tetrachloroaurate (III) tetrahydrate (HAuCl4 center dot 4H(2)O). Formation of gold nanoparticles on silica gel was confirmed by using Field Emission Scanning Electron Microscope (FE-SEM) and Energy Dispersive X-ray Fluorescence Spectrometer (EDX). In this study, particles size distribution and coverage ratio of gold on silica gel were investigated.

Acidic wastewater from industrial discharge is generally treated by neutralization. Before neutralization or water treatment, selective recovery of valuable compounds is necessary to reduce the environmental impact of this acid waste. As a contribution to the development of a novel acidic wastewater treatment, oxalic acid is set as target material which is found in acid waste from the metalworking industry. Crystallization of oxalic acid in the presence of sulfuric acid has rarely been reported. Since this acid waste also contains aluminum ions, the effect of sulfuric acid and aluminum ions on oxalic acid solubility and crystallization was clarified. As a result, sulfuric acid concentration affected the oxalic acid solubility, but aluminum ions had no influence. Oxalic acid was precipitated in columnar shape by cooling crystallization from sulfuric acid aqueous solution with aluminum ions.

Acidic wastewater from industrial discharge is generally treated by neutralization. Before neutralization or water treatment, selective recovery of valuable compounds is necessary to reduce the environmental impact of this acid waste. As a contribution to the development of a novel acidic wastewater treatment, oxalic acid is set as target material which is found in acid waste from the metalworking industry. Crystallization of oxalic acid in the presence of sulfuric acid has rarely been reported. Since this acid waste also contains aluminum ions, the effect of sulfuric acid and aluminum ions on oxalic acid solubility and crystallization was clarified. As a result, sulfuric acid concentration affected the oxalic acid solubility, but aluminum ions had no influence. Oxalic acid was precipitated in columnar shape by cooling crystallization from sulfuric acid aqueous solution with aluminum ions.

Efficient and simple methods for gene integration into various plants have been studied by many researchers. The particle gun method using fine metal particles is one of the most potent technologies. However, it is difficult to control the particle size distribution and shape of the metal particles and, thus, to design and create adequate particles of suitable quality for the gene-supporting media. Here, reduction crystallization of nanometer- and submicron-sized Au was investigated in order to clarify the effects of the seeding and reaction conditions on the sizes and shapes of Au particles. The seed size has an influence on the surface roughness of the Au nanoparticles. Experiments to form Au particles were also performed using pH-controlled ascorbic acid. The pH has a great influence on the size and shape of nano/submicron Au particles and the mechanism of reduction crystallization.

The effects of the presence of a polyelectrolyte on the polymorphism and particle size and shape of calcium carbonate crystals during reactive crystallization were investigated. Crystals were created by the single-jet reaction crystallization method. When polyacrylic acid (PAA) was added, the polymorphism and particle size and shape were different for each molecular weight of PAA and each experimental method. When sodium carboxymethylcellulose was added, the polymorph became different from those made by adding PAA and the particle sizes and shapes were different for each concentration. As a result, it is suggested that the method to achieve supersaturation, such as type of feeding, feed rate, kinds of polyelectrolyte and their concentration, may affect the polymorphism and particle size and shape of calcium carbonate.

The effects of polyacrylic acid (PAA) on the crystallization of carbonates were investigated, revealing a great influence of PAA on the shape, size and polymorph type of the carbonate crystals. Carbonate crystallization was performed through reaction crystallization in a single-jet system. The obtained crystals were measured and characterized by scanning electron microscopy and X-ray diffraction. In lithium carbonate, PAA especially influenced the growth phase, inhibited agglomeration and changed the crystal shape into high-aspect rods. In addition, the degree of the growth inhibition effect was molecular weight dependent and the inhibition effect was also different on each face. In calcium carbonate, an improvement of the monodispersity was observed with miniaturization, under particular conditions. Elongated calcite was found under a slow supersaturation rate. In addition, the molecular weight of PAA affected the polymorph selectivity. Therefore, PAA affected the crystallization phenomena of carbonates, and prospected crystals were obtained by changing the operation conditions.

The effect of a small amount of amino acid additives on the pseudopolymorphism of L-arginine hydrochloride (LAHCL) in aqueous solution is reported. Results confirm that L-alanine (L-Ala) has a stabilizing effect on the crystals of the anhydrate form of LAHCL at low temperature. Intriguingly, the stabilizing effect was observed even when L-Ala was added after a large amount of LAHCL had formed. In contrast, no stabilizing effect with D-Ala could be stated, suggesting that the stereochemistry of the additives is an important factor. In addition to the stereochemistry, also the length and bulkiness of the alkyl side-chain of the amino acids were found to be significant factors. Based on these results, a mechanism is proposed for stabilization of anhydrate LAHCL crystals by amino acid additives.

The effects of sensitivity and resolution of a nucleation detector on induction time were mathematically analysed. The induction time was defined here as the time at which the number density of crystals nucleated under isothermal conditions had reached the minimum detectable number density of crystals (N/M)(det). The value of (N/M)(det) depends on the detector used, and therefore can be called the detector sensitivity. Meanwhile, the detector resolution is defined as the minimum detectable crystal size L-d. The equation for induction time t(ind) was derived for a simplified case wherein secondary nucleation and concentration reduction were both neglected. For a more general case where such a simplification cannot be made, the induction time t(ind) was calculated numerically. The sensitivity and resolution had effects on induction time. The induction time increased as the sensitivity decreased (i. e., the value of (N/M)(det) increased). It also increased with a decrease in the resolution (i. e., an increase in the minimum detectable size L-d). The effect of nucleus size L-0 on induction time t(ind) was also analysed. The analysis suggested that the induction time in an actual experiment, where the minimum detectable size L-d would be much larger than the nucleus size L-0, was independent of nucleus size itself but was affected by the resolution L-d. The interfacial energy of a crystal nucleus in solution that is deduced from the widely used plot of ln t(ind) vs. 1/(ln S)(2) (S: supersaturation ratio) was pointed out to be questionable. The effect of agitation rate (or stirrer speed) on induction time was also discussed.

Specific small amounts of amino acids caused agglomeration of L-valine (L-Val) crystals during evaporative crystallization from aqueous solutions. The agglomeration of L-Val occurred only under acidic condition when guest amino acids satisfied several conditions. Only L-form amino acids that have carboxylic acid groups and sufficiently long alkyl chain in the side-chains could induce agglomeration of L-Val. The length of alkyl chain in the side-chains controls the degree of agglomeration. Data indicated only 0.5wt% of L-2-aminoadipic acid, which has a similar chemical structure to L-glutamic acid (L-Glu), produced the large agglomerates &gt
1000μm. The particle size was ∼500μm when using the same amount of L-Glu. Based on the results from previous tests and this paper, the whole mechanism for the L-Val agglomeration in the presence of specific guest amino acids has been revealed. © 2013 WILEY-VCH Verlag GmbH &amp
Co. KGaA, Weinheim.

Each XRD peak intensity of CaSO4 center dot 2H(2)O crystals changes according to their morphologies. This research clarifies the relationship between XRD peak intensity and morphologies on CaSO4 center dot 2H(2)O crystals synthesized by reaction crystallization with various additives. As a result, as XRD relative intensity of (021) face increases, average longitude and aspect ratio decrease and needle-like or plate-like large crystals transform into granular microcrystals. (C) 2013 The Authors. Published by Elsevier By. All rights reserved.

Double-jet reactive crystallization of SrSO4 was carried out in the presence of polyethylenimine (PEI). A simple kinetic model of primary nucleation as well as crystal growth was investigated under the condition of producing monodisperse microcrystals. Furthermore, surface free energy in the solution of PEI was estimated. PEI addition causes growth inhibition leading to smaller sizes and modifies the Gibbs free energy gap required for occurring nucleation. The effect of polyethylenimine (PEI) addition on nucleation and growth of SrSO4 is determined and a simple kinetic model is proposed. Time-dependent behaviors of crystal size and crystal number are statistically analyzed by a nonlinear least-square program. Kinetic aspects under the condition of obtaining monodisperse crystals are discussed. © 2013 WILEY-VCH Verlag GmbH &amp
Co. KGaA, Weinheim.

Anionic polyelectrolyte effects on the lithium carbonate crystallization phenomena were investigated. Li2CO3 crystals were obtained by reactive crystallization with seed crystals. Polyelectrolytes were dissolved into the reactive field before the reaction. Obtained crystals were observed with scanning electron microscopy (SEM) and crystal size and agglomeration degree were measured by the SEM images. The results show that Li 2CO3 crystallized different shape and size from absence of polyelectrolyte in those reactive fields. Especially polyacrylic acid (PAA) improved on the agglomeration of the crystals and shaped them high aspect needles. Thus other experimental conditions including PAA molecular weight and concentration, reaction time, supersaturation by Li concentration were investigated in addition. As a result, obtained crystals were not different in each PAA molecular weight reactive fields. Meanwhile PAA concentration has optimum range. Li2CO3 formed less agglomeration and higher aspect around 1 g/l. In the concentration, Li2CO3 did not agglomerate regardless of aging time and Li concentration. Moreover crystals became rectangle shape in higher Li concentration.(020) face intensity of the rectangle shape crystals increased according to XRD pattern. PAA affected the facial growth. These results may provide a method of morphological change and clearly crystallization of Li2CO3. © 2012 Elsevier B.V. All rights reserved.

D-chiro-inositol (DCI) is prepared by the immobilized enzyme reaction which uses myo-inositol (MI) as the substrate and the conversion rate is about 13%. The aim of this study was to develop a separation method for high purity DCI crystals from a reaction solution including low purity DCI only by the crystallization process. We succeeded in separating DCI crystals of 96% purity by water cooling crystallization, but it was presumed that scale-up was difficult. Although we tried anti-solvent crystallization similar to water cooling crystallization, high purity DCI crystals were not obtained. Therefore, we proposed the crystallization separation process by controlling metastable zones. The purity of a desired compound is controlled by this process, because solid-liquid separation is achieved before crystallization of compound in metastable zone. By the crystallization using this method, the DCI crystals of 97% purity were obtained. Although the yield per batch is about 50%, the actual yield is improved as the last mother liquor returns into the process of the following batch. When this process was repeated, the purity and the yield of DCI were reproduced and the robustness of this process was proved. It is expected that scale-up of this process will be successful, and this purification method could be applicable to similar systems such as separation of isomers and analogs. (C) 2012 Elsevier B.V. All rights reserved.

D-chiro-inositol (DCI) is prepared by the immobilized enzyme reaction which uses myo-inositol (MI) as the substrate and the conversion rate is about 13%. The aim of this study was to develop a separation method for high purity DCI crystals from a reaction solution including low purity DCI only by the crystallization process. We succeeded in separating DCI crystals of 96% purity by water cooling crystallization, but it was presumed that scale-up was difficult. Although we tried anti-solvent crystallization similar to water cooling crystallization, high purity DCI crystals were not obtained. Therefore, we proposed the crystallization separation process by controlling metastable zones. The purity of a desired compound is controlled by this process, because solid-liquid separation is achieved before crystallization of compound in metastable zone. By the crystallization using this method, the DCI crystals of 97% purity were obtained. Although the yield per batch is about 50%, the actual yield is improved as the last mother liquor returns into the process of the following batch. When this process was repeated, the purity and the yield of DCI were reproduced and the robustness of this process was proved. It is expected that scale-up of this process will be successful, and this purification method could be applicable to similar systems such as separation of isomers and analogs. (C) 2012 Elsevier B.V. All rights reserved.

Au nanoparticles are expected for the media to transfer genes into plants. However, the control of particle size distribution (PSD) and shape of Au nanoparticles is too difficult to design and prepare particles with suitable quality for the gene supporting media. Reduction crystallization experiments were performed in aqueous solution in order to clarify the effect of feeding conditions such as feeding profile, feeding rate, and feeding amount on PSD and shape of Au nanoparticles. Ascorbic acid (AsA) was selected as a reducing agent because it is safe for plants. Au particles of 50 nm, 50-200 nm, and 150-400 nm were obtained in batch operation, single-jet, and double-jet, respectively. Moreover, in single-jet and double-jet, the mean size of the obtained Au particles increases with the decrease of feeding rate or the increase of feeding amount. It is concluded that PSD of Au nanoparticles can be controlled in the range of 50-400 nm by changing feeding conditions of AsA and HAuCl4 aqueous solution. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg.

Relationship between magnesium ammonium phosphate (MAP) crystal properties and the filtration ability of hollow fiber membrane (HFM) were investigated. Phosphorus recovery process by crystallization has a problem that it produces a large amount of fine crystals. So improvement of the crystallization process by combining with filtration was discussed. MAP crystals were obtained by batch reaction crystallization and the filtration characteristics were investigated. The filtration was evaluated by the specific filtration resistance (αc) on HFM. Filtered slurry was prepared with each suspension density and crystal size distribution. The solution was filtered at constant pressure of 0. 02 MPa and the filtration time on each filtrated volume was recorded. As a result, αc decreases exponentially with suspension density increasing from 0. 25 g/L to 0. 5 g/L and αc decreases moderately with suspension density increasing from 0. 5 g/L to 1. 5 g/L. αc of large crystals decreases exponentially at less suspension density than αc of small crystals does. Also, αc increases as the ratio of the fractured crystals increases. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg.

In the dissolution step of spent nuclear fuel, there is a world-concern problem that zirconium molybdate hydrate precipitates as a byproduct, and accumulates in some reprocessing equipments. In order to prevent this accumulation, we have developed a new method based on the controlled reaction crystallization of zirconium molybdate hydrate (ZMH) in the reprocessing solution, followed by solid liquid separation. In order to measure the particle size of ZMH, batch crystallization experiments were conducted by varying nitric acid concentration and operating temperature. In result, almost all particle sizes scatter around 1 mu m on average, despite the higher concentration of nitric aid and operating temperature, and then small particles grow up as an aggregate sticking to the crystallizer. Moreover, polymorph and color changing were observed by varying the concentration of nitric acid and reaction time. These results suggest that crystal color and adhesiveness are closely related to the particle size of ZMH. And the control of nitric acid concentration and small particle growth would be the useful technique to prevent the ZMH sticking.

Plastid transformation methods have been developed for 20 plant species. However, only a few plant species, such as tobacco and lettuce, have been used in applied studies because transformation efficiencies are extremely low in other species. Plastid transformation has been mainly performed by particle bombardment using 0.6-mu m gold particles as microcarriers of the transformation vector. Because the target materials in some plant species are undeveloped proplastids rather than fully developed chloroplasts, optimizing microcarrier size for the target size is a major consideration. In this study, we evaluated the availability of gold particles (0.07, 0.08, 0.1, 0.2, and 0.3 mu m) that were smaller than those used for plastid transformation in previous studies. We obtained stable plastid transformants of tobacco with sufficient efficiency using all the tested small gold particles as the same level as 0.6-mu m gold particles, even the smallest (0.07 mu m). The average number of transformants obtained with 0.3-mu m particles (9.3+/-4.6 per plate) was the highest among the tested gold particles. Because small gold particles were revealed to be sufficient for plastid transformation in a model tobacco plant, it is suggested that choosing appropriate small-sized gold particles which have never been used before will improve plastid transformation in many plant species.

The specific interaction between L-valine (L-Val) and L-glutamic acid (L-Glu) in the process of evaporative crystallization from an aqueous solution has been investigated. It was found that only 2.0% (wt/wt) of L-Glu against the total amount of L-Val was required to induce significant agglomeration of L-Val. Interestingly, the agglomeration was only induced under acidic conditions, suggesting that the electrostatic interaction was an effective factor for the agglomeration process. As well as the electrostatic interaction, the length of the amino acid side chain was identified as another important factor. In addition, we confirmed that the incorporation rate of L-Glu into L-Val crystals was different during the nucleation and crystal growth stages. Based on these results, a mechanism has been proposed for the interaction of L-Glu and L-Val during the agglomeration process. © 2012 Elsevier B.V. All rights reserved.

Metastable zone widths (MSZWs) and induction times were determined with numerical simulations on an unseeded aqueous solution. The simulated MSZWs and induction times were significantly affected by secondary nucleation caused by nuclei grown crystals. However, this secondary nucleation-mediated effect on the MSZWs and induction times was negligibly small at high cooling rates and at high supercoolings, respectively. The primary nucleation parameters k(b1) and b1 in the rate expression B-1 = k(b1)(Delta T)(b1), where B-1 is the nucleation rate and Delta T is supercooling, were deduced by applying mathematical Kubota models to the determined MSZWs and induction times, respectively. Correct primary nucleation parameters (i.e., the same values as those input for the simulations) were deduced only under the condition of neglected secondary nucleation. The simulation results suggest that, in actual experiments, the proper primary nucleation parameters b1 and k(b1) can be deduced from the MSZWs and induction times if these were measured under the condition of neglected secondary nucleation. In addition, an experiment with a slow stirrer speed (low secondary nucleation rate) and with a high sensitivity detector (earlier detection of the MSZW and induction time) were recommended for the deduction of correct primary nucleation parameters.

The effects of the sensitivity and resolution of a detector on metastable zone width (MSZW) were theoretically studied by using analytical and numerical methods. The detector sensitivity and the detector resolution were defined here as the minimum detectable number density of crystals (N/M)(det) and the minimum detectable size of crystals, respectively. Both the sensitivity and resolution had significant effects on MSZW. The MSZW became larger as the sensitivity was decreased (i.e., the value of (N/M)(det) was increased). It also became larger with a decrease in the resolution (i.e., an increase in the minimum detectable size). The effect of the resolution was less significant than that of the sensitivity. The effect of nucleus size on MSZW is also discussed. The MSZW reading in an actual experiment, where the minimum detectable size is expected to be much larger than the nucleus size, was suggested not to depend on nucleus size.

In this article, manganese and zinc compound formation via reactive crystallization has been summarized. In this process, the metal sulfate solution was reacted with the sodium carbonate solution according to the double-jet method. Some particle properties such as crystal size, shape, agglomeration rate, and metal ion concentration in the effluent have been examined by controlling the pH in the initial reaction field, the concentration of the metal ions in the stock solution, or the flow rate of the solution. The size of formed manganese carbonate particles increases with an increase in the feeding speed and the metal ion concentration in stock solution. This is due to the fact that particle growth is strongly affected by the metal ion supersaturation in the reaction solution. Meanwhile, the manganese carbonate particle recovery rate increases with an increase in the feeding rate and a decrease in the metal ion concentration. The size of zinc oxide particles formed continuously changes with the initial pH. The above experiments indicate that the recovered crystal size and surface roughness, as well as the metal ion recovery rate and monodispersion, are controlled, to some extent, by regulating the reaction conditions.

Each XRD peak intensity of CaSO4ï \2H2O crystals changes according to their morphologies. This research clarifies the relationship between XRD peak intensity and morphologies on CaSO 4ï \2H2O crystals synthesized by reaction crystallization with various additives. As a result, as XRD relative intensity of (021) face increases, average longitude and aspect ratio decrease and needle-like or plate-like large crystals transform into granular microcrystals. © 2013 The Authors.

Reactive crystallization for separation and recovery of divalent metal ions from wastewater using a semi-batch crystallizer has been developed. In this process, metal carbonates are produced by reacting metal sulfate solution with sodium carbonate solution. Nickel and copper ions are crystallized under particular initial pH conditions but the product shapes are not regular. Consequently, sphere seeds have been used as nucleus-generating agents and their growth mechanism has been examined. When providing a particular amount of seeds before crystallization, metal substances piled up on the surface of the seeds, maintaining the form sphere, and the production of fines was restricted. The metal removal rate through reactive crystallization was similar to 99.9?% on average. This operation proved to be suitable for application in industrial wastewater treatment and for recycling of metal materials.

Crystallization is a suitable process for selective separation of a target ion since ions can be removed and recovered as purified and stable materials. Methods of recovery and recycling of phosphate and fluoride ions have been investigated to determine the optimum crystallization conditions like supersaturation, temperature, pH, impurities, and kind of solvents. As a result, by selecting the optimum crystal operation conditions for each wastewater composition, spherical-shape crystals with desired purity and size are obtained and generation of sludge is minimized.

The effect of ultrasonic irradiation on nucleation phenomena in the heat storage material CH3COONa center dot 3H2O was investigated by measuring the nucleation probability and induction time. The experimental results show that the concentration of CH3COONa should be operated in the optimum range for CH3COONa center dot 3H2O-selective crystallization. Furthermore, the nucleation probability increased and the induction time decreased with increasing energy input. Consequently, the optimum conditions of ultrasonic irradiation of CH3COONa center dot 3H2O are 53?wt-% CH3COONa, 3.0?W of energy input, and ?T = 1068?K.

Precipitation of silver nanocrystals was carried out in a poly(acrylic) acid (PAA) solution by using a single-jet crystallizer. The influence of the feeding rate, the injection position and the PAA dosage on the crystal size distribution (CSD) was clarified. The precipitated silver nanocrystals agglomerate with each other, forming an agglomerated microcrystal. In the presented case, smaller feeding rates caused smaller crystal sizes and narrower CSD widths. PAA, which is a water-soluble polyelectrolyte, successfully inhibited agglomeration and crystal growth, and decreased the crystal size and the CSD width. Thus, this idea may also facilitate the production of other nano-/microcrystalline particles.

Simulation of induction time for nucleation was performed under isothermal conditions for unseeded aqueous solutions of different concentrations. The effects of stirrer speed and growth rate on induction time were both explained with the proposed secondary nucleation-mediated mechanism. The effect of stirrer speed N-r was incorporated into the simulation with an empirical relation of k(b2) proportional to N-r(j), where k(b2) is the coefficient in the secondary nucleation rate equation B-2 = k(b2) (Delta T)(b2)mu(3), Delta T is supercooling, j and b2 are empirical constants and mu(3) is the third moment of crystal size distribution. The simulated induction time decreased with an increase in stirrer speed at lower supercoolings, while it remained unchanged at higher supercoolings. Such action of stirrer speed was similar to that observed in the literature data. The growth rate effect was considered to be caused by a faster increase in the secondary nucleation rate via a faster increase in mu(3). The simulated induction time decreased with an increase in crystal growth rate. This type of growth rate effect is completely different from the existing mechanism considering the time needed for invisible nuclei to grow to a detectable size.

The influence of polyethyleneimine (PEI) addition on the crystal size distribution (CSD) of Au was investigated. PEI is a water-soluble cationic polyelectrolyte acting as a reducer of AuCl(4)(-) and a stabilizer of precipitated Au nanocrystals. The CSD can be controlled by the PEI dosage, and an increase in PEI dosage decreased both the size and the size distribution width of the obtained Au nanocrystals. The idea of PEI-assisted reductive crystallization of Au may be helpful in the production of nanometals by using a simple batch crystallizer.

The effect of melt crystallization on inorganic hydrate for purification of crystals containing liquid and solid impurities was investigated. Melt crystallization is generally applied to purify organic crystals. In the case of inorganic crystals, it is cost-ineffective because of the higher melting point. However, some inorganic crystals, i.e., hydrate crystals, can be applied to melt crystallization because of the lower melting point. Hydrate crystals containing impurities were prepared and melt crystallization was carried out to investigate the purification mechanism on inorganic crystals. Liquid impurity in target crystals was removed by sweating and washing with melt. Solid impurity was also separated with melt flow, supported by mixing operations. It was considered that the purification mechanism is differently dependent on the state of impurity.

The objective of this study is to investigate the effect of organic solvents on pseudopolymorph transformation kinetics for clarifying the transformation phenomenon. In our previous study, we observed anhydrate and dihydrate crystals of myo-inositol in water and/or an ethanol-water system and transformation phenomena. However, we could not determine the detailed transformation mechanism in organic solvents. Therefore, we attempted adding seed crystals to different alcohol solvents, which resulted in the transformation of seed crystals of a dihydrate into anhydrate crystals. The transformation kinetics increased with a decrease in the alkyl carbon number in the solvents and also with an increase in the ethanol mass fraction. During the transformation process, fine anhydrate crystals were observed on the surface of dihydrate crystals, and the dihydrate crystals were found to dissolve and gradually decrease in size. On the basis of these results, we propose that the hydrophilic nature of organic solvents is a significant factor determining the pseudopolymorph transformation kinetics of myo-inositol. The transformation phenomena proceeded easily upon the addition of dehydrate seed crystals, as if the solvent had the driving force for the crystallization of a stable polymorph. We classified this unique mechanism as a "solvent-induced transformation."

The objective of our study is to investigate the effect of melt crystallization on inorganic hydrate for purification of crystals including impurity. Melt crystallization is widely applied in the chemical and food industry to purify organic crystals by separating impurities inside the crystals. The target crystals are mainly organic crystals; however, some inorganic crystals are considered for purification by melt crystallization, because of having lower melting point as hydrate crystals. Therefore, we prepared hydrate crystals including impurities and carried out melt crystallization to investigate the purification mechanism on inorganic crystals. Aluminum nitrate nonahydrate was selected as purification target and strontium nitrate was selected as liquid impurity. As solid impurity, we selected barium nitrate. In conclusion, liquid impurity in target crystals was removed by sweating and washing with melt. Moreover, it was considered that the purification mechanism differs depending on the state of the impurity, and melt crystallization is an effective tool for purification the inorganic hydrate crystals.

The cooling crystallization of borax decahydrate has been investigated for the influence of temperatures on solubility, induction period and yield in order to establish the limits of conditions. Crystal morphology of borax decahydrate was studied by optical microscopy. Characterization of the crystals was performed by X-ray diffraction. The solubility curves were determined within the range of 0 to 25 degrees C. The induction period was extremely short in seeded experiments compared with unseeded experiments. The yield was found to increase with decreasing temperatures. Microscopy observation revealed that as-grown crystals were significantly elongated in a direction parallel to the c-axis of the monoclinic system. The X-ray diffraction analysis indicated that the (002) plane of monoclinic system grew faster than the (120) plane at temperatures of 5 and 9 degrees C. The results indicate that the temperature limit of borax decahydrate crystallization is 9 degrees C.

Reactive crystallization of SrSO4 was performed in the presence of polyethylenimine (PEI) using a double-jet crystallizer. PEI dosage suggested important dependence on crystal size distributions (CSDs) leading to obtain micron-sized crystals with mono-dispersed distribution. A plausible role of PEI was considered to be a multiple inhibitor of growth, continuous nucleation and agglomeration. PEI might be an effective polyelectrolyte additive for the production of mono-dispersed fine crystals. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Nano-sized gold particles were prepared in a solution containing polyethylenimine (PEI) utilizing a batch reactor. PEI acts as a reducing agent as well as a stabilizing agent of nanoparticles. The effects of initial concentration of PEI on the mean particle diameter, coefficient of variation (C.V.), growth rate, nucleation rate and the number of nuclei were studied. The particle diameter of gold decreased markedly with increasing initial concentration of PEI, from 3.3 mu m to a minimum value of about 5 nm. The observed decrease of particle diameter was considered to be caused by the growth-inhibiting effect of PEI, which affects the conclusive number of nuclei. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

The selective polymorph control in sulfamerazine (SMZ) using ultrasonic irradiation was investigated. Firstly, the behavior of polymorphs in the absence of ultrasonic irradiation with various degrees of supersaturation was monitored. As a result, only metastable form-I crystallized at the primary nucleation stage and crystal growth of only form-I was recognized. The nucleation rate of stable form-II was very small, and the transformation from form-I to form-II hardly occurred. Therefore, it is easy to obtain form-I without ultrasonic irradiation, as it does not depend on the level of supersaturation. Secondly, the behavior of polymorphs with various degrees of ultrasonic energy and supersaturation was monitored. As a result, only form-I was obtained in the case of small ultrasonic energy. However, in addition to the nucleation of form-I, an unknown form-III and/or the recognized form-II are induced to nucleate under the influence of the ultrasonic energy in the case of large ultrasonic energy. Eventually, all forms changed to form-II within a short period of time. Therefore, polymorph control of SMZ can be achieved easily by supplying an appropriate amount of ultrasonic energy. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Reactive crystallization of SrSO4 was performed in the presence of polyethylenimine (PEI) using a double-jet crystallizer. PEI dosage suggested important dependence on crystal size distributions (CSDs) leading to obtain micron-sized crystals with mono-dispersed distribution. A plausible role of PEI was considered to be a multiple inhibitor of growth, continuous nucleation and agglomeration. PEI might be an effective polyelectrolyte additive for the production of mono-dispersed fine crystals. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Micronized SrSO4 crystals having monodispersed/narrow distributions were produced with a controlled double-jet reactive crystallizer. Polyethylenimine (PEI) had the role of a suitable controller of supersaturation and following crystallization phenomena, and then led to agglomeration-less homogeneous crystalline qualities. Especially, the PEI imines seemed to adjust the number of nucleates, and also physical gel networks seemed to contribute to the inhibition of further particulate agglomeration. The current paper mainly demonstrated the influence of PEI addition on the resulting properties, e.g. sizes and size distribution widths. Therefore the polyelectrolyte-assisted technique will develop as a build-up process contributing to provide high-value nano/micro-powders having the desired crystalline qualities.

Precipitation of monodispersed SrSO4 particles was carried out in the presence of polyethylenimine (PEI). PEI additions varied some particulate properties, e.g., sizes, shapes, size distribution widths, and agglomeration ratios. The present paper mainly focuses on the influence of PEI dosage on crystal size distributions. PEI-assisted double jet techniques require no difficult controls of feeding rates, therefore, this idea will be applicable to precipitation of other inorganic compounds for the purpose of producing monodispersed nano-/microparticles.

Micronized BaSO4 particles with a narrow size distribution were produced by using a double-jet reactive crystallizer. Polyethylenimine (PEI) acted as a growth/agglomeration inhibitor at a high PEI dosage, hence the particle size and size distribution width decreased, and BaSO4 crystals with the desired qualities were obtained. Similar results were obtained in previous studies in which of SrSO4 and PbSO4. We believe that our method, which involves the use of PEI, can be employed for the production of various inorganic sulfates in which the particles have a monodisperse size distribution.

Micron-sized SrSO4 particles having mono-dispersed/narrow distributions have been produced with a double-jet semi-batch reactive crystallizer. Slow molar feedings over a short time maintained proper supersaturation levels and result in narrow distributions due to the prevention of agglomeration growth of small primary precipitates. Furthermore, polyethylenimine (PEI) is a suitable growth/agglomeration inhibitor for sulfate precipitation, e. g., SrSO4 and PbSO4, and effectively reduced particle sizes leading to single-micron products. Besides feeding conditions, in the present work, the influence of PEI dosage on crystal size distributions (CSDs) is investigated. The controlled double-jet feeding using a polyelectrolyte additive such as PEI will be a powerful methodology to obtain agglomeration-free uniform micro-powders as a final solid product.

In experiments on U crystallization in a dissolver solution containing Cs, there is concern that Cs and Pu(IV) nitrate complex are deposited on the UNH crystal in the dissolver solution at the time of the U crystallization. The characteristics of generation of Cs and Pu(IV) nitrate complex with dissolver solution of MOX fuel were examined. This complex was obtained as a precipitate by mixing dissolver solution of MOX fuel and CsNO(3) solution, and was identified as dicesium tetravalent plutonium hexanitrate, Cs(2)Pu(NO(3))(6) by concentration analysis and XRD. The precipitate has a tendency to be generated at high HNO(3) concentrations. Thermal analysis shows that the precipitate is stable below 245 degrees C, and a weight loss of 10.29 +/- 0.23% is observed between 245 and 297 degrees C. This result indicates the decomposition of Cs(2)Pu(NO(3))(6) to Cs(2)PuO(2)(NO(3))(4), With these properties, the UNH crystal should melt at the condition between 60 and 100 degrees C and be separable from the Cs complex by filtration. This suggests a new method of crystal purification allowing higher decontamination of UNH crystal in the U crystallization process. (C) 2009 Elsevier B.V. All rights reserved.

A controlled double-jet reactive crystallization technique using a PEI (polyethylenimine) additive has been conducted to produce agglomeration-free micro-particles of SrSO4 with narrow and mono-dispersed size distributions. PEI successfully inhibits rapid/continuous nucleation due to a complexation with strontium ions before nucleation occurs, and enables realization of perfect separation of nucleation and growth. Our idea to obtain fine particles with desired size distributions will introduce a new potential for contributing to enhance high-valued material properties.

A controlled double-jet reactive crystallization technique using a PEI (polyethylenimine) additive has been conducted to produce agglomeration-free micro-particles of SrSO4 with narrow and mono-dispersed size distributions. PEI successfully inhibits rapid/continuous nucleation due to a complexation with strontium ions before nucleation occurs, and enables realization of perfect separation of nucleation and growth. Our idea to obtain fine particles with desired size distributions will introduce a new potential for contributing to enhance high-valued material properties. © 2010 The Society of Chemical Engineers, Japan.

Micron-sized SrSO4 particles having mono-dispersed/narrow distributions have been produced with a double-jet semi-batch reactive crystallizer. Slow molar feedings over a short time maintained proper supersaturation levels and result in narrow distributions due to the prevention of agglomeration growth of small primary precipitates. Furthermore, polyethylenimine (PEI) is a suitable growth/agglomeration inhibitor for sulfate precipitation, e. g., SrSO4 and PbSO4, and effectively reduced particle sizes leading to single-micron products. Besides feeding conditions, in the present work, the influence of PEI dosage on crystal size distributions (CSDs) is investigated. The controlled double-jet feeding using a polyelectrolyte additive such as PEI will be a powerful methodology to obtain agglomeration-free uniform micro-powders as a final solid product.

In order to examine the decontamination behavior of the Pu and fission products (FPs) that contained with the uranyl nitrate hexahydrate (UNH) crystals in the U crystallization process, experiments were carried out using mixed oxide (MOX) fuel dissolver solution. The experiments confirmed that Eu was adequately decontaminated by washing the UNH crystals with a HNO(3) solution. However, Ba crystallized as Ba(NO(3))(2) and the washing was ineffective for the decontamination of Ba. High HNO(3) and Pu concentrations in the mother liquor, the decontamination factor (DF) of Cs was low because Cs precipitated with Pu as Cs(2)Pu(NO(3))(6). The Pu clearly showed a reasonable DF because the amount of Pu in the dissolver solution was higher than that of Cs. Almost all the amount of Pu remains in the mother liquor except the one in the Cs(2)Pu(NO(3))(6) precipitate.

Micronized BaSO4 particles with a narrow size distribution were produced by using a double-jet reactive crystallizer. Polyethylenimine (PEI) acted as a growth/agglomeration inhibitor at a high PEI dosage, hence the particle size and size distribution width decreased, and BaSO4 crystals with the desired qualities were obtained. Similar results were obtained in previous studies in which of SrSO4 and PbSO4. We believe that our method, which involves the use of PEI, can be employed for the production of various inorganic sulfates in which the particles have a monodisperse size distribution.

固形物のメタン発酵処理では，窒素，リンを高濃度に含む消化液が発生する．筆者等は，水処理系のリン負荷低減，メタン発酵槽内部やその周辺機器のスケール防止，リン資源の回収を目的として，消化液からリン酸マグネシウムアンモニウム（MAP）を積極的に析出させて回収するプロセスを考案した．プロセスは，晶析工程，液体サイクロンによる分離工程，洗浄工程，低温乾燥工程からなる．本報では，固形物濃度が数%含まれる消化液を対象としたMAPの最適な晶析操作条件と乾燥条件を把握すると共に，処理量2 m³/hの実規模スケールの装置を作製し，16か月に渡り実証試験を行った結果を報告する．<br>MAPを液体サイクロンで分離するために，晶析工程では核発生を抑制する必要がある．ラボ実験より，リアクタ内のMAPの流動状態を良好に保つこと，低過飽和度で操作すること，種晶充填量あたりのMAP晶析速度を適切に保つことで，MAPの核化が抑制され，結晶成長が優先的となることを見出した．また，乾燥工程では，乾燥温度を70&deg;C以下にすることでMAPは転移することなく現状の形態を維持できることが明らかとなった．一連のプロセスの実証試験において，晶析工程でのPO₄&ndash;P除去率は85%以上であり，良好に反応を行うことができた．また，反応したリンのうち，核化した割合は約10%であり，反応したリンの約90%は種晶表面で成長したので，良好に消化液からMAPを分離することができた．乾燥工程から回収したMAPの含水率は0.1%以下，MAPの純度は92.6%，有害金属の含有量は肥料取締り法で定める基準値以下であったことから，MAPの肥料製品としての高い品質を保っていることが確認できた．

The nucleation behavior of an active pharmaceutical ingredient (API) is investigated in semi-batch drowning-out crystallization. A methanol solution of the API was fed in a short period into a well-mixed anti-solvent at low temperature. The effect on nucleation behavior of the amount of seed crystals and concentration of API methanol solution to be fed was investigated using in-line particle monitoring technique (FBRM). Despite the presence of seed crystals in anti-solvent into which the API solution was fed, nucleation took place after an induction period from feeding in some experiments, and it was found that the addition of seed crystals is effective to control the induction period and to enhance nucleation after the induction period. As for feed concentration, at high feed concentration, generation of nuclei during feeding was observed and then a supersaturated slurry of fine particles was obtained; however, at low feed concentration, anti-solvent became clouded locally during feeding and then clear supersaturated solution was obtained. At high feed concentration, it was also observed from time courses of FBRM chord count for several size classes that fine particles generated during feeding grew very slowly during the induction period, and rapid nucleation took place accompanied with agglomeration of fine particles and subsequent dispersion with generating nuclei.

The effect of ultrasonic irradiation on the polymorph control of sulfamerazine (SMZ) in acetonitrile at 21 degrees C was studied. In the primary nucleation stage without ultrasonic irradiation, metastable form-I crystallized primarily from the supersaturated solution. Then, only form-I grew, although slowly, and the SMZ concentration reached the saturation point of form-I. SMZ showed a very low solvent-mediated polymorphic transformation rate owing to the small difference in solubility between its metastable form-I and stable form-II. The transformation from form-I to form-II hardly occurred, even when the suspension of form-I was maintained at 21 degrees C for a few days or weeks. Therefore, it was easier to obtain form-I than form-II by controlling only the degree of supersaturation. On the other hand, form-II could be obtained by supplying a certain amount of ultrasonic energy in the primary nucleation stage. In such cases, the nucleation rate and crystal growth rate were relatively high; the SMZ concentration reached the saturation point of form-II within one day. Furthermore, the solvent-mediated transformation was enhanced by ultrasonic irradiation. The SMZ concentration decreased when periodic ultrasonic irradiation was carried out a few hours after the SMZ concentration reached the saturation point of form-I. Finally, form-I transformed to form-II. Thus, for the production of either form, the polymorph of SMZ can be controlled with or without ultrasonic irradiation. (c) 2008 Elsevier B.V. All rights reserved.

Present state and strategies are summarized on the recovery of anions in the wastewater, based on crystallization engineering. Anion which gives undesirable influence to the environment has been removed by coagulation and precipitation methods to produce a large amount of sludge, requiring wide space for its disposal. Recently steep increase in the price of the resources and deep concern about drying-up of resources have accelerated recovery of ions in the wastewater. Consequently many researches have been done to selectively separate a desirable ion. Crystallization is one of the suitable processes for this purpose, because it can remove and recover ions as the form of purified and stable crystals. In application of crystallization to the wastewater treatment, solid-liquid equilibrium, metastable zone width (MZW), degree of supersaturation, crystallization kinetics (crystal growth, nucleation and so on) and selection of seeds and desirable seed amounts should be given. Examples and strategies on phosphate and fluoride recovery are shown.

Removal and recovery of phosphorus from sewage in form of MAP ( magnesium ammonium phosphate) have attracted attention from the viewpoint of eutrophication prevention and phosphorus resource recovery as well as scaling prevention inside digestion tanks. In this work, phosphorus recovery demonstration tests were conducted in a 50m(3)/d facility having a complete mixing type reactor and a liquid cyclone. Digested sludge, having 690 mg/L T-P and 268 mg/L PO4-P, was used as test material. The T-P and PO4-P of treated sludge were 464 mg/ L and 20 mg/ L achieving a T-P recovery efficiency of 33% and a PO4-P crystallization ratio of 93%. The reacted phosphorus did not become fine crystals and the recovered MAP particles were found to be valuable as a fertilizer. A case study in applying this phosphorus recovery process for treatment of sludge from an anaerobic-aerobic process of a 21,000 m(3)/d sewage system, showed that 30% of phosphorus concentration can be reduced in the final effluent, recovering 315 kg/d as MAP.

The authors have been engaged in the development of a phosphorus recovery system capable of maintaining high recovery efficiencies, with the chemical cost suppressed. This time, they conducted demonstration tests of a fluidized bed magnesium ammonium phosphate reactor provided with a seeder reactor for the supernatant from anaerobic digestion using a pilot experimental plant with a wastewater treatment capacity of 20 m(3)/d. For the digestion supernatant with a phosphorus concentration of approximately 300 mg/L, the treated water phosphorus concentration was 10 to 25 mg/L, and the phosphorus recovery efficiency was more than 90%. Relative to the chemical cost in the case of magnesium chloride, the chemical cost in the case of magnesium hydroxide is approximately 40%. Thus, with the new system, it was possible to reduce the running cost while maintaining high recovery efficiencies.

下水放流水のリン濃度低減、リン資源回収の観点からリンを除去・回収する方法として、リン酸マグネシウムアンモニウム (MAP) の形態で回収するMAP法がある。筆者らは、消化汚泥に直接マグネシウムを添加してMAPを晶析・分離回収するプロセスを開発した。本プロセスについて、基本的な晶析操作条件の検討、パイロットスケールの実証試験、実機スケールの実証試験を行ったところ、消化汚泥の全リンの30%以上、結晶化したリンの95%以上に相当する量を回収することができた。また、このプロセスを処理量21, 000m³/dの嫌気性消化槽を有する下水処理場に設置した場合、放流水のリン濃度の30%以上を低減可能であること、315kg/dのMAPを回収可能であることを示した。更に、消化槽内のスケール抑制の可能性を見出した。

A process for recovering phosphorus from wastewater in form of magnesium ammonium phosphate (MAP) crystals using a fluidized bed reactor was investigated. The phosphorus recovery ratio was found to be influenced by the particle size of the MAP crystals, as well as the reaction pH, inlet ammonium and phosphorus concentration. The optimum operation conditions for the fluidized bed reactor to achieve the maximum recovery rate of phosphorus were organized in terms of the supersaturation ratio and reaction pH. The best supersaturation ratio was found to be 3.7. The optimum reaction pH depended on the inlet phosphorus concentration and was found to be 7.9 when the inlet PO4-P was 230 mg.L-1. A continuous treatment of filtrate from digested sludge was performed based on these optimum operation conditions and using a newly proposed fluidized bed system. The fluidized bed system has a seeder, which allowed control of the particle size distribution inside the crystallization tower. A recovery ratio higher than 90% was achieved for a long period of the demonstration test in this new fluidized bed system.

The purpose of our study is to clarify ultrasonic primary nucleation phenomena for controlling final product size by adjusting the number of primary nuclei. In our previous study, the effect of ultrasonic irradiation on the number of nuclei was investigated under the same supersaturated condition, as a result two novel phenomena were observed. First, there is a region where ultrasonic irradiation inhibits primary nucleation. Second, a specific amount of energy is needed to activate primary nucleation. From this result, it was expected that the ultrasonic energy needed to activate primary nucleation has a certain relationship to the energy necessary to form a stable nucleus. Therefore, we investigated the following: whether ultrasonic irradiation inhibits and activates primary nucleation at various degrees of supersaturation, whether final crystal size relates to the number of nuclei, and whether the ultrasonic energy needed to activate primary nucleation relates to the energy necessary to form a stable nucleus. First, we found that ultrasonic irradiation inhibits and activates primary nucleation at various supersaturated degrees. Second, we found that final crystal size increases or decreases depending on the number of nuclei. Therefore, it was indicated that ultrasonic energy could yield the desired crystal size by inducing suitable nucleation. Third, we found that the ultrasonic energy needed to activate primary nucleation decreases with a decrease in the energy necessary to form a stable nucleus. From this, we can propose criteria for determining the effect of ultrasonic irradiation on primary nucleation by showing diagrams correlating Delta G(crit) with E-crit. (c) 2006 Elsevier B.V. All rights reserved.

Crystals of lead sulfate were precipitated in solutions of various polyelectrolyte polymers (acidic, neutral, and basic polymers) using a double-jet crystallizer. Polyetyleneimine (PEI) basic polymer controlled both the nucleation rate and crystal growth rate, and enabled the production of fine monodispersed crystals. The on-line measurement of the variation in the lead concentration indicated that PEI lost its effect when a certain amount of the reactants N-tot was supplied. Interaction between lead ions and PEI was detected by NMR analysis, which suggested that lead ions made some kind of complex with PEI. The values of N-tot correlated well with the weight of PEI in the solution, regardless of the feed flow rate and reactant concentration, as shown in the correlative equation N-tot = k W-0.49. It was suggested that PEI could no longer control the precipitation rate when the amount of reactants supplied exceeded N-tot. Thereafter, rapid nucleation occurred. Precipitation with PEI could be controlled by a certain amount of PEI in a ground solution in order to produce monodispersed fine crystals. These results give an effective idea of how to create various nm size crystals.

フッ素イオンを晶析法により分離除去する方法において，晶析に適用できるフッ素イオン濃度とカルシウムイオン濃度の範囲を検討した．まず，種晶を添加しない実験で，初期フッ素イオン濃度とカルシウムイオン濃度を変えて，撹拌後のフッ素イオン濃度を検討して，フッ素イオンがカルシウムイオンと反応してフッ化カルシウムの沈殿を生成してフッ素イオン濃度が低下しはじめるときの初期フッ素イオン濃度とカルシウムイオン濃度の関係を求めた．次に，種晶を添加した実験を，種晶を添加しない実験と同一条件で行って，フッ素イオンがカルシウムイオンと反応してフッ化カルシウム結晶を種晶上に析出してフッ素イオン濃度が低下しはじめるときの初期フッ素イオン濃度とカルシウムイオン濃度の関係を求めた．この両者の実験結果から，フッ化カルシウムの過溶解度線を作成して，溶解度線と過溶解度線の間の準安定域を明らかにした．この結果から，晶析可能なフッ素イオン濃度は，3 mmol/l以下であることがわかった．<br>実験後のフッ化カルシウム結晶のXRDを測定した．その測定結果から，実験後のフッ化カルシウム結晶のメインピーク値が文献値と一致し，フッ化カルシウムであることが確認できた．

Crystals of strontium sulfate were precipitated in a solution of polyethylenimine (PEI) using a double-jet crystallizer. PEI, as a crystal growth modifier, controlled both the nucleation rate and the growth rate, and enabled to produce fine monodispersed crystals. Both acetic acid and hydrochloric acid were used as a pH-controlling agent. Especially, in case of using hydrochloric acid, highly monodispersed crystals (coefficient of variation, C.V.□ 0.1) were produced within fairy wide operation conditions.

Crystals of lead sulfate were precipitated in the solutions of various polyelectrolyte polymers (acidic, neutral and basic polymers) using a double-jet crystallizer. Polyetyleneimine (PEI), basic polymer, controlled both nucleation rate and crystal growth rate, and enabled to produce fine mono-dispersed crystals. The on-line measurement of the variation in the lead concentration indicated that PEI lost its effect, when a certain amount of the reactants (Ntot) was supplied. Interaction between lead ions and PEI was detected by NMR analysis, to suggest that lead ions made some kind of complex with PEI. The values of Ntot were correlated well with weight of PEI in the solution, regardless of the feed flow rate and reactant concentration, as shown in the correlative equation Ntot = k W0.49 (Figurel). It was suggested that PEI could no longer control the precipitation rate, when reactants were supplied over the amount of Ntot. And after that, the rapid nucleation occurred. Precipitation with PEI could be controlled by a certain amount of PEI in a ground solution in order to produce mono-dispersed fine crystals. These results idea would give an effective idea to crate various nm size crystals.

In the reaction crystallization of calcium carbonate using a batch reactor system with aqueous CaCl2 and Na2CO3 at room temperature, the selective polymorphic control of crystalline calcium carbonate into calcite was achieved by adjusting the operating conditions. The polymorphic ratio of calcite and vaterite nucleated from amorphous calcium carbonate (ACC) was significantly influenced by the initial supersaturation and solution pH, thereby resulting in a different phase transformation rate for the product powder from unstable vaterite to stable calcite. With a high supersaturation and low solution pH, the phase fraction of calcite decreased owing to the favorable transformation of ACC into vaterite during the early stage of the crystallization. Thereafter, the phase fraction of calcite increased as a result of the transformation of vaterite into calcite as the aging progressed. However, with a low supersaturation and high solution pH, calcite was exclusively observed throughout the reaction time without any recrystallization of vaterite. The decrease in the polymorphic ratio of vaterite in the product powders with the reaction time indicated the disappearance of vaterite due to its dissolution at a low initial supersaturation, which matched well with the morphological change in the polymorphs obtained by a scanning electron microscopy analysis. Meanwhile, at a high initial supersaturation, the polymorphic changes from vaterite to calcite did not produce any morphological transformation.

The antisolvent crystallization of sodium chloride was carried out in batches to observe crystallization phenomena using ethanol as an antisolvent. To decrease high local supersaturation generated by the addition of antisolvent, the authors have proposed a new idea by choosing high ethanol concentration operational conditions. Obtained crystals seemed to be unagglomerated and monodispersed in the optimum range of ethanol concentration. From the observation of nucleation phenomena, it was considered that nucleation induced by the antisolvent addition occurred due to the local supersaturation generated at the boundary of the starting and feed solutions. On the other hand, crystal growth is considered to proceed by the supersaturation generated by sufficient mixing between the starting and feed solutions. Average crystal size increased with the increase of σR. The number of produced crystals increased with the increase of the starting solution concentration C. The induction period for nucleation tended to decrease with increase of C and σR. Since the number of produced crystals depended on C, nucleation was considered to be influenced by local mixing between the starting and feed solutions.

In the reactive crystallization of hydroxyapatite (HAP) done with CaCl2, KH2PO4 and NaOH solutions at the reaction temperature of 60°C in a semi-batch reactor, the relationship of the crystalline properties of nanosized HAP powders with the operational conditions was experimentally investigated. The crystallinity of needle-like HAP powders was enhanced with decreasing OH- ion composition and reactants concentration, which corresponded well with the increase in the crystal size, but had nothing to do with the aging of the product suspension. Even though the supersaturation level was predicted not to be influenced by the OH- ion composition, the crystal growth of the HAP powders was striking at low OH- ion composition, thereby resulting in larger HAP with high crystallinity. Comparing the growth orientation of the HAP powders before and after sintering, the crystal growth was preferentially promoted on the face of (002) in the direction of the crystallographic c-axis, especially at low OH- ion composition and reactants concentration during the crystallization, and it was transferred on the (300) face along the a-axis after sintering at 1000°C for 3 h, which seem to be caused by the unbalanced grain coalescing according to the crystallographic axes of HAP.

The antisolvent crystallization of sodium chloride was carried out in batches to observe crystallization phenomena using ethanol as an antisolvent. To decrease high local supersaturation generated by the addition of antisolvent, the authors have proposed a new idea by choosing high ethanol concentration operational conditions. Obtained crystals seemed to be unagglomerated and monodispersed in the optimum range of ethanol concentration. From the observation of nucleation phenomena, it was considered that nucleation induced by the antisolvent addition occurred due to the local supersaturation generated at the boundary of the starting and feed solutions. On the other hand, crystal growth is considered to proceed by the supersaturation generated by sufficient mixing between the starting and feed solutions. Average crystal size increased with the increase of a. The number of produced crystals increased with the increase of the starting solution concentration C. The induction period for nucleation tended to decrease with increase of C and a. Since the number of produced crystals depended on C, nucleation was considered to be influenced by local mixing between the starting and feed solutions.

In the reactive crystallization of hydroxyapatite (HAP) done with CaCl(2), KH(2)PO(4) and NaOH solutions at the reaction temperature of 60degreesC in a semi-batch reactor, the relationship of the crystalline properties of nanosized HAP powders with the operational conditions was experimentally investigated. The crystallinity of needle-like HAP powders was enhanced with decreasing OH(-) ion composition and reactants concentration, which corresponded well with the increase in the crystal size, but had nothing to do with the aging of the product suspension. Even though the supersaturation level was predicted not to be influenced by the OH- ion composition, the crystal growth of the HAP powders was striking at low OH- ion composition, thereby resulting in larger HAP with high crystallinity. Comparing the growth orientation of the HAP powders before and after sintering, the crystal growth was preferentially promoted on the face of (002) in the direction of the crystallographic c-axis, especially at low OH- ion composition and reactants concentration during the crystallization, and it was transferred on the (300) face along the a-axis after sintering at 1000degreesC for 3 h, which seem to be caused by the unbalanced grain coalescing according to the crystallographic axes of HAP.

The effect of O-3 treatment and AOP (Advanced Oxidation Processes) treatment on the decomposition of endocrine disruptors were investigated by using continuous type pilot plant. Reaction kinetic evaluations of these processes were also carried out. In this study, the endocrine disruptors were classified into 2 groups: (1) DXNs: dioxins and (2) EDs: endocrine disruptors other than dioxins. For the case of DXNs decomposition, highly concentrated DXNs in a incinerator washwater were degraded by UV/O-3 combined treatment. Influence of O-3 dosage and forms of DXNs on the reaction rate constant were evaluated. The incinerator washwater was sampled from a scrubber, which was used for the flue gas treatment of a garbage incinerator facility.
For the case of EDs decomposition, the effect Of O-3 dosage on the reaction rate constant were investigated during O-3 treatment of secondary treated sewage. Also, a comparison was made on the degradability for the above 2 groups. The following results were obtained. (1) The DXNs contained in the incinerator washwater had different decomposition properties depending on the particle size of suspended solid. Above a particle size of 1.0 mum, the reaction rate constant was relatively small and the DXNs were relatively non-degradable. On the other hand, when suspended solid particle size was below 1.0 mum, the reaction rate constant was large and the DXNs were relatively degradable. (2) The amount of decomposed DXNs per consumed O-3 increased with the increase of DXNs concentrations in the influent and higher DXNs decomposition efficiencies were obtained. (3) The reaction rate constant in the EDs decomposition was larger than that in the DXNs decomposition, and the EDs were found to be relatively easy to be decomposed. Once DXNs on the suspended solid particle size larger than 1.0 mum in the incinerator washwater were non-degradable, we found that they should be filtered and concentrated separately prior to the AOP treatment to ensure an efficient treatment.

In this study, experiments using a fluidized crystallizer with added seed, were performed, to observe the crystal growth and nucleation phenomena of MAP, by changing the degree of supersaturation. The average growth rate of suspended seed crystals correlated relatively well with the degree of supersaturation to obtain the quantitative correlation equation. Also the average crystal growth rate was in good accordance with the crystal growth rate of the small crystals which comprised the seed crystal. This showed that crystal growth was preceeded by the growth of individual crystal is acting as one single seed crystal. But over a certain degree of supersaturation, the surface condition of grown seed crystals was observed to become rough. Concentration of fines was recognized to correlate with the degree of supersaturation, and excess fines were produced over the critical supersaturation, which was the same as when the surface condition of crystals became rough. The critical supersaturation was considered to offer some design criteria for stable operation in the magnesium ammonium phosphate crystallization in the environmental field. (C) 2002 Elsevier Science B.V. All rights reserved.

In this study, Ni²⁺ removal from electroless nickel plating wastewater (A. co., Ltd.) by reduction crystallization was investigated, to make clear the effect of seeds specific surface area on the Ni²⁺ removal characteristics. Although the main reaction in this research is the same as the one in electroless nickel plating, the authors have proposed reduction crystallization in which wastewater from electroless nickel plating contacts with suspended nickel powder, to remove and recover Ni²⁺. The results could be obtained on the relationship between the pH change profile and recovery efficiency in the reaction process, in which nickel powders having various specific surface area were used as seeds. Experimental results were discussed, considering surface conditions of grown nickel and the behavior of produced fines. With a constant 10% NaOH solution feed rate, the pH profile changed in the process of Ni²⁺ reduction, by changing the specific surface area of seeds, which means that Ni²⁺ removal efficiency was affected by the specific surface area of seeds. When constant pH7 was maintained, higher removal efficiency (0.99; Ni²⁺ concentration in the treated water 2.5×10^-2g·dm^-3) could be obtained, although the specific surface area of Ni seed powder varied. Specific surface of seeds, based on the roughness of seed crystal, was suggested to be an effective factor on the Ni metal coating behavior on the seed surface and also the phenomena of fines production in the process of Ni deposition.

In the seeded crystallization of yttrium oxalate from a metastable supersaturated solution, the growth mechanism was observed to become modified by variations in agitation and additive concentration. From the desupersaturation curve, the crystal growth rate was estimated and described using a power law of supersaturation (R-T = k(gDelta)C(p))Without an additive in the metastable solution, the overall growth rate coefficient, K-g, increased with an increase in the agitation speed while the growth rate order, p, was almost independent of the agitation speed. When the additive sodium tripolyphosphate was used to inhibit crystal growth, the desupersaturation in the solution was substantially retarded and the growth rate order varied up to about 2.5 with an increase in the additive concentration. Using a two-step growth model, the kinetic parameter dependencies of the crystal growth of yttrium oxalate, such as the mass transfer coefficient, surface integration order, and surface integration coefficient, were estimated in relation to the agitation speed and additive concentration. The mass transfer coefficient increased with an increase in the agitation, whereas the surface integration coefficient was independent of the agitation speed. However, as the additive concentration in the solution increased, the surface integration coefficient was reduced while the mass transfer coefficient remained almost invariant. The change in the rate-determining step by the additive was examined using an effectiveness factor. It was shown that the effect of the additive on the surface integration followed a Langmuir type isotherm. (C) 2002 Elsevier Science B.V. All rights reserved.

In the seeded crystallization of yttrium oxalate from a metastable supersaturated solution, the growth mechanism was observed to become modified by variations in agitation and additive concentration. From the desupersaturation curve, the crystal growth rate was estimated and described using a power law of supersaturation (R-T = k(gDelta)C(p))Without an additive in the metastable solution, the overall growth rate coefficient, K-g, increased with an increase in the agitation speed while the growth rate order, p, was almost independent of the agitation speed. When the additive sodium tripolyphosphate was used to inhibit crystal growth, the desupersaturation in the solution was substantially retarded and the growth rate order varied up to about 2.5 with an increase in the additive concentration. Using a two-step growth model, the kinetic parameter dependencies of the crystal growth of yttrium oxalate, such as the mass transfer coefficient, surface integration order, and surface integration coefficient, were estimated in relation to the agitation speed and additive concentration. The mass transfer coefficient increased with an increase in the agitation, whereas the surface integration coefficient was independent of the agitation speed. However, as the additive concentration in the solution increased, the surface integration coefficient was reduced while the mass transfer coefficient remained almost invariant. The change in the rate-determining step by the additive was examined using an effectiveness factor. It was shown that the effect of the additive on the surface integration followed a Langmuir type isotherm. (C) 2002 Elsevier Science B.V. All rights reserved.

The effect of O3 treatment and AOP (Advanced Oxidation Processes) treatment on the decomposition of endocrine disrupters were investigated by using continuous type pilot plant. Reaction kinetic evaluations of these processes were also carried out. In this study, the endocrine disrupters were classified into 2 groups: (1) DXNs: dioxins and (2) EDs: endocrine disrupters other than dioxins. For the case of DXNs decomposition, highly concentrated DXNs in a incinerator washwater were degraded by UV/O3 combined treatment. Influence of O3 dosage and forms of DXNs on the reaction rate constant were evaluated. The incinerator washwater was sampled from a scrubber, which was used for the flue gas treatment of a garbage incinerator facility. For the case of EDs decomposition, the effect of O3 dosage on the reaction rate constant were investigated during O3 treatment of secondary treated sewage. Also, a comparison was made on the degradability for the above 2 groups. The following results were obtained. (1) The DXNs contained in the incinerator washwater had different decomposition properties depending on the particle size of suspended solid. Above a particle size of 1.0 μm, the reaction rate constant was relatively small and the DXNs were relatively non-degradable. On the other hand, when suspended solid particle size was below 1.0 μm, the reaction rate constant was large and the DXNs were relatively degradable. (2) The amount of decomposed DXNs per consumed O3 increased with the increase of DXNs concentrations in the influent and higher DXNs decomposition efficiencies were obtained. (3) The reaction rate constant in the EDs decomposition was larger than that in the DXNs decomposition, and the EDs were found to be relatively easy to be decomposed. Once DXNs on the suspended solid particle size larger than 1.0 μm in the incinerator washwater were non-degradable, we found that they should be filtered and concentrated separately prior to the AOP treatment to ensure an efficient treatment. Copyright ©2002 The Society of Chemical Engineers.

In lysozyme precipitation by polyacrylic acid (PAA) with different molecular weights, the lysozyme separation was predicted using Smoluchowski's collision theory and the micromixing limitation model, plus the model predictions were compared with the experimental data from an MSMPR reactor. Since, in Smoluchowski's theory, ideal mixing was assumed in the solution, the lysozyme separation was only predicted to depend on the PAA properties, such as the PAA dosage and its molecular weights. However, in the micromixing limitation model, the lysozyme separation was represented as being affected by the operational conditions, including the mean residence time and the mixing intensity, in addition to the PAA properties. The difference between the lysozyme separations predicted by each model significantly increased at short residence time and low agitation speed. When compared with the experimental data obtained with various PAA properties and operational conditions, the degree of the lysozyme separation predicted by the micromixing limitation model was found to be in better consistency with the experimental data than that done by Smoluchowski's theory because the operational conditions as well as the PAA properties were included in describing the lysozyme-PAA combination in the reactor.

In polyelectrolyte precipitation of lysozyme, the combination mechanism between lysozyme and polyacrylic acid (PAA) at various experimental conditions was investigated from the stoichiometric coefficient at equilibrium in a batch reactor. At the underdosed condition of PAA to lysozyme, the lysozyme-PAA combination was performed by the electric charge neutralization and polymer bridging between lysozyme and PAA. As the PAA dosage decreased and its molecular weight increased, the bridging effect of PAA became more significant in the lysozyme-PAA combination because the more lysozyme was captured by the polymer bridging of PAA. The stoichiometric coefficient of the lysozyme-PAA combination, which was estimated from the lysozyme separation, was affected by both the PAA dosage and its molecular weight, but the effect of agitation was not observed. The linear equations were derived from the relationship between the stoichiometric coefficient and the dosage at three different PAA molecular weights of 2.0 × 10³, 4.5 × 10⁵ and 4.0 × 10⁶, and well consistent with the experimental data.

Wastewater treatment after electroless nickel plating runs has been known to be difficult and this has been a subject of worldwide concern. Discarding wastewater of electroless nickel plating into sea was prohibited under the London Dumping Treaty since 1996. We have studied on recovering nickel from wastewater by reduction crystallization. In this study, the characteristics of nickel ion removal and recovery were investigated in the process of reduction crystallization using a laboratory scale batch crystallizer (500 ml), in order to propose a new process for wastewater treatment from nickel plating. In the reduction crystallization, which can use hypophosphite ion as a reducing agent for nickel ion in the wastewater, nickel ion could be recovered as a form of nickel metal by seeding nickel powder having large specific surface area.

Crystal growth experiments were performed in a suspension system of sodium borate decahydrate crystals, to observe the surface status of crystals in the process of their growth, and to obtain the correlative equation of the factors ( degree of supercooling, linear velocity in the crystallizer and revolution rate of the agitator) affecting secondary nucleation rate. It is also made clear that the average secondary nucleation rate based on the operation time is affected by the surface status of the growing crystals, and its rate osccillates against the operation time. This oscillation phenomena are discussed, based on the qualitative model of two series processes consisted of a diffuison stage and a surface reaction stage.

The applicability of tandem mass spectrometry to the quality analysis of metal-surface protect surfactants without any pretreatment or purification of the sample solution was investigated. Three typical spectra were constructed and verified by FAB CID-MS/MS using sodium n-dodecylsulfate (anionic surfactant), tetradecyl dimethylbenzylammonium chloride (cationic surfactant) and heptaethylene glycol mono-n-dodecyl ether (nonionic surfactant) as a model. The FAB CID-MS/MS spectra of metal-surface protect surfactants provided useful structural information that analyte surfactants have a polyoxyethylene structure, which has been identified as a nonionic surfactant. The authors concluded that FAB CID-MS/MS will be a good analytical method for direct quality analysis without any pretreatment or purification of the metal-surface protect surfactant for industrial use.

In this study, lead sulfate particles were produced in a batch crystallizer, by feeding lead nitrate and sodium sulfate solutions (concentration : 0.025-0.4 mol/l) continuously to the vicinity of an agitator rotating at 400 rpm from individual feed pipes. The batch crystallizer contained a solution of Pb 10-2 mol/l, gelatin 5 wt% and acetic acid 3.48 mol/l. In the crystallization process, crystals were sampled over time to measure crystal size distribution based on number, and to observe the shape and surface condition of crystals. From the results of experiments, it was shown that the position, where the nucleation phenomenon was detected in the equipment, changed for a feed concentration 0.4-0.5 mol/l. This phenomenon was considered with respect to the supersaturation ratio in the equipment. Moreover, in the range of experimental conditions, where relatively monodispersed fine particles were produced, it was observed that crystals of unstable state were fromed in the beginning of the reaction, but after that they were transformed to a stable rhombic shape. The stable crystals were considered to grow while consuming all the reactant components in the equipment. Also, an experimental equation was presented showing that formation rate of nuclei to become product crystal was proportional to the fifth power of the feed supersaturation ratio. © 1995, The Society of Chemical Engineers, Japan. All rights reserved.

最近, 一般廃棄物最終処分場で浸出水中のカルシウムが問題となっている。本研究ではカルシウムイオン濃度1.2から14.1mol・m^-3までの原水の軟化処理を種晶に高炉スラグを用いたペレット流動床法により行った。軟化処理の薬剤には水酸化ナトリウムと炭酸水素ナトリウムを用いた。晶析反応は即時に完結し, 最初のサンプリング位置 (0.1m) でカルシウム濃度は装置出口濃度まで低下した。<BR>カルシウムイオンの除去率は49%から60%であった。処理水の濁度は30度以下で, pHは7.6から8.0の範囲であった。流動層内は完全混合とみなせたので, 次の簡易特性モデル式を適用することができた。<BR>Co-C=Ko・C・θ<BR>Co: 原水カルシウムイオン濃度 [mol・m-3] C: 処理水カルシウムイオン濃度 [mol・m^-3]<BR>θ: 滞留時間 [h] Ko: カルシウムイオン除去速度定数 [h^-1]

In recent years considerable attention is given to the development of methods for the preparation of microcrystals with a narrow crystal size distribution (CSD). One promising technique, been developed for the preparation of silver halides crystals, is controlled double-jet precipitation (CDJP). In the CDJP the cation and anion solutions are added simultaneously through separate input lines to a stirred solution oi a lyophihc polymer. The formation and growth of monodisperse microcrystals in the bulk of crystallizer and the nucleation of unstable nuclei or primary particles formed near jets occur simultaneously during the whole run. The monodisperse particles are prepared if these unstable nuclei or primary particles continuously disappear from the system by controlled Ostwald ripening or controlled agglomeration, and the matter serves as a source for the growth of constant number of stable particles. The objective of this contribution is to survey this unique precipitation technique while the concept of CDJP can be used in general for the precipitation of various sparingly soluble salts.

Effect of collision by agitation of impeller on secondary nucleation rate of K-Alum was studied in the range of nucleation rate increasing with impeller rotational speed. Fluidized bed of seed crystal with a paddle-type impeller was used as the crystallizer, and the height of seed bed was adjusted to be the same as the width of the impeller to allow for seed crystals to be directly agitated by the impeller. The total number of secondary nuclei generated was observed by direct counting under a microscope. Secondary nucleation rates are correlated with supersaturation, and these powers of supersaturation are in the range 1.3-1.6, depending upon impeller rotational speed and impeller diameter. These values of 1.3-1.6 are smaller than the power of 3.3 obtained by fluidized seeds and by seeds of the minimum size to be able to produce secondary nuclei, and are almost identical with that for crystal growth rate. This result is discussed in terms of the damaged surface repairing model reported by Larson et al. New equation of secondary nucleation rate by impeller agitation is derived by improving the semi-theoterical model of secondary nucleation rate in a stirred tank reported by de Jong et al., and experimental data obtained in this study are correlated by that equation. © 1979, The Society of Chemical Engineers, Japan. All rights reserved.