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.

The solution structures in the tetra-n-butylammonium bromide (TBAB) aqueous solution relate closely with the memory effect. In the present study, the behavior derived from the existence of the residual solution structures after TBAB semiclathrate hydrate (TBAB SCH) decomposition was investigated with two methods. One is a high-precision differential scanning calorimetry. The heat capacity of a TBAB aqueous solution with memory effect was slightly larger than that after the memory effect disappeared. The larger heat capacity implies the existence of solution structures. The other is a small-angle X-ray scattering (SAXS). In the first cooling process, strong scattering derived from rapid crystallization was observed at 263.6 K. In the second cooling process where the TBAB aqueous solution exhibited the memory effect, the scattering intensity gradually increased and became remarkably strong at a temperature (approximately 277 K) higher than 263.6 K. In the second cooling process, the invariant Q, which corresponds to electron density fluctuation, increased gradually until crystallization, whereas, in the first cooling process, the change of the invariant Q was quite small until crystallization. The increase of invariant Q implies the existence of 10–100 nm density fluctuation, which is consistent with the cluster size (10–20 nm) previously observed with electron microscopy in the same system.

To clarify the inevitability of the relationship between the melting point (T-m= 291 K) and the heat of fusion (Delta H-f=135 kJ/kg) of potassium acetate dihydrate, a potential latent heat storage material, a quantitative examination of the relationship was made in terms of the structural formula. First, four pairs of salts comprising Na+ or K+ with the same given anion were investigated, for all of which the degree of hydration and the dehydration transition temperature of the hydrate was known. It was found that the dehydration temperature of the potassium salt was generally 20.50 K lower than that of the sodium salt. It was also found that the dehydration temperature, that is T-m, was lower as the ratio of Stokes radius of the salt ion in aqueous solution to the ion radius in crystal structure decreased. Next, the entropy change Delta S-f (=Delta H-f/T-m) of the hydrate during fusion was expressed as a combination of entropy change Delta S-LHO of water during fusion and the mass fraction Phi(w) of the water of crystallization in the hydrate. With this combination, a simple relational expression between T-m and Delta H-f was derived. Application of this expression to the measured data for 18 different hydrates, it was indicated that the numerical value of Delta H-f could be estimated with a relative standard deviation of +/- 0.212 when the structural formula and the T-m value of a hydrate were both known. Through this, the inevitability of the correspondence between the Delta H-f value and T-m for potassium acetate dihydrate was also confirmed.

Hydrated salts are promising latent heat storage materials because of their high heat storage density per unit volume. However, few hydrated salts have melting points in the temperature range suitable for cooling and air conditioning (273-303 K). In this study, the relationship between the temperature and the hydration number of potassium acetate hydrate and its potential applicability as a latent heat storage material were investigated. From direct observation of potassium acetate aqueous solution, the generally accepted crystallization properties of 0.5 and 1.5 hydrated salts were confirmed. It was also suggested that potassium acetate dihydrate would crystallize upon cooling the solution to 229 K. The melting point of the dihydrate was 291 K, and its heat of fusion was 135 kJ/kg. This heat of fusion is intermediate position among those of six other hydrated salts that have melting points within the range of 285. 294 K. Potassium acetate dihydrate thus has comparable potential to those salts for application as a latent heat storage material for cooling and air conditioning.

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.

Nano-sized metal particles have been actively investigated. Although the synthesis methods of nano-sized metal particles have been made remarkable progress through many researches, in many cases, heat treatment is required. In order to promote industrial utilization, non-heating, simple and inexpensive synthesis methods are required. In the present study, nano-sized metal particles composed of Ag, Au, Ir, or Pd were prepared in an aqueous solution with a simple and non-heating way. After a noble-metal carboxylate was completely dissolved in the quaternary ammonium carboxylate aqueous solution, nanoparticles composed of the noble metal appeared in the aqueous solution. Since this operation is extremely simple as well as non-heating because the noble-metal carboxylate only dissolves into the quaternary ammonium carboxylate aqueous solution. The nano-sized metal particles were observed by Scanning Electron Microscope (SEM) or Scanning Transmission Electron Microscope (STEM) with the freeze-fracture replica method and characterized with Energy Dispersive X-ray Spectroscopy (EDX) and Electron Energy Loss Spectroscopy (EELS).

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.

Disodium hydrogen phosphate dodecahydrate is a latent heat storage material which is expected to be applied to indoor air conditioning and floor heating. However, because the dodecahydrate melt in the heat storage state does not nucleate easily even if it is cooled to a temperature below its melting point, it makes difficult to operate the latent heat storage system to release the stored heat at its melting point. In order to solve this supercooling problem, generally, nucleating agents are added. But their nucleation promoting abilities were still insufficient, as far. In the present study, with the aim of extracting the physical properties necessary for functioning as a nucleating agent, the added reagents were fixed their anion component to carbonates and sulfates and the strength of their promoting abilities was investigated by thermal cycle experiments. As a result of examining the relationship between the strength of the promoting ability quantified by defining as a supercooling ratio and the solubility of the reagent in water, in the reagent inducing heterogeneous nucleation by generating precipitate into the melt, it was found that the strength of the promoting ability was clearly related to the solubility. Further, the facts that the effects of nucleation promoting and nucleation inhibiting by the anion and the cation, respectively, both generated due to dissolving to the melt, were arithmetic addition, that the larger difference of ion radius between such cation and the sodium ion made stronger the inhibiting effect by the cation, and that the promoting effect by the heterogeneous nucleation and the inhibiting effect by the cation were also arithmetic addition were revealed.

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.

Disodium hydrogen phosphate dodecahydrate is a latent heat storage material which is expected to be applied to indoor air conditioning and floor heating. However, because the dodecahydrate melt in the heat storage state does not nucleate easily even if it is cooled to a temperature below its melting point, it makes difficult to operate the latent heat storage system to release the stored heat at its melting point. In order to solve this supercooling problem, generally, nucleating agents are added. But, in spite of the many studies on the development of the agent thus far, their nucle-ation promoting abilities were still insufficient. In the present study, with the aim of extracting the physical properties necessary for functioning as a nucleating agent, the added reagents were fixed to sodium salts and the strength of their promoting abilities was investigated by thermal cycle experiments. As a result of examining the relationship between the strength of the promoting ability quantified by defining as a supercooling ratio and the acid dissociation constant of the anion, in the anion having a higher dissociation constant compared with the mono-hydrogen phosphoric ion con-stituting the dodecahydrate, it was found that the anion having a larger number of the dissociation constant exhibited a stronger promoting ability. In addition, as a mechanism for the appearance of the promoting effect, it was considered that the ionic environment in the dodecahydrate melt was destabilized due to the basic action of added anions, and the energy barrier for the nucleation was reduced.

Disodium hydrogen phosphate dodecahydrate is a promising candidate for latent heat storage material due to its fast crystal growth rate and high heat storage density per unit volume. In its practical application, however, a key technical problem has been to eliminate the formation of phase segregation and concentration polarization owing to the cyclic operation of heat storage and heat release. In the present study, in order to understand the influence of the formation of such phase segregation and concentration polarization on the heat release behavior of the heat storage material, the dodecahydrate melt samples formed them were prepared artificially and their solidification behavior were observed directly by eye. Additionally, the crystal growth rates of the dodecahydrates were measured and the features of each solidification behavior were evaluated quantitatively. As a result, the crystal growth rates were dropped to about 40% in both cases of the dodecahydrate melt diluted by phase segregation and the upper layer of the melt diluted by concentration polarization. Further, in another case of the lower layer of the melt concentrated by concentration polarization, the growth rate was depressed to about 20%. It was suggested that the formation of phase segregation and concentration polarization brought about not only a latent heat reduction, but also a heat releasing speed depression.

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.

0 Melt systems of sodium carbonate decahydrate (melting point T-m,T-0 = 304.5 K, latent heat of fusion Delta Hf,0 = 153 kJ/kg, both measured) and of a salt hydrate eutectic E(P-C) (T-m,T-0 = 298 K, Delta H-f,H-0 = 213 kJ/kg, both also measured) consisting of 0.6 mol/mol sodium carbonate decahydrate and 0.4 mol/mol disodium hydrogen phosphate dodecahydrate are attracting attention as potential latent heat storage materials. Changes in the melting point Tm and the latent heat Delta H-f were measured for the two melt systems with readily soluble additives. By using simplified empirical formulae, the abilities of melting point depression a(me) and latent heat reduction b(me) for each additive were quantified. The numerical values of these abilities were different for each additive, but their ratio b(me)/a(me) was almost the same regardless of the kind of additive, showing an eigenvalue of each melt system. In addition, a comparative study was performed of b(me)/a(me) values including those of the calcium chloride hexahydrate system (Watanabe, 2017) and the disodium hydrogen phosphate dodecahydrate system (Watanabe and Hirasawa, 2018b). It was found that, independent of the kind of melt system, the relative degree of melting point depression [1-(T-m/T-m,T-0)] and the relative degree of latent heat reduction [1-(Delta H-f/Delta H-f,(0))], respectively normalized by T-m,T-0 and Delta H-f,H-0, showed an almost constant numerical relationship represented by the following expression.1-(Delta H-f / Delta H-f,H-0) = 21.4 [1-(T-m / T-m,T-0)]

Technology employing melting point depression can be useful for extending the applicable temperature range of a latent heat storage material. In this study, the melting points T m and latent heats of fusion ΔH f were measured in systems of disodium hydrogen phosphate dodecahydrate (with measured values of T m,0 =308.5 K and ΔH f,0 =227 kJ/kg), which is especially utilized as a medical heat-retention material, with five additives that are readily soluble in the dodecahydrate melt: tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, and sodium dihydrogen phosphate dihydrate. By using the simplified empirical formula proposed previously expressing the relation between additive concentration and the degree of melting point depression (Watanabe and Hirasawa, 2017) or the degree of latent heat decrease (Watanabe, 2017), the abilities of each additive to depress melting point and decrease latent heat were numerically expressed. These values differed from one additive to another and appeared to be specific to each. However, the numerical relation expressed in the equation below was found to hold almost invariably regardless of the additive(forumala Presented).

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.

Based on the idea that eutectic formation is a useful technology for controlling the melting points of latent heat storage materials over a wide temperature range, experimental studies were carried out on the pseudobinary mixtures of sodium carbonate decahydrate and disodium hydrogen phosphate dodecahydrate, both of which are also heat storage materials. From the distribution of melting points of the mixtures of varying composition determined from the heating curve, the phase diagram was developed as a single eutectic type, and the melting point of the eutectic was found to be 298 K. For specifying the eutectic composition, two methods were examined: one by using the empirical formula of the melting point depression, and the other by utilizing the change in the latent heat of fusion. The eutectic composition as a mole fraction of disodium hydrogen phosphate dodecahydrate was estimated to be 0.40 mol/mol by the former method and 0.37 to 0.38 mol/mol by the latter. These values closely match the 0.4mol/mol derived from the hypothesis that the eutectic would be formed by equivalent exchange of dissociated ions in the melt of salt hydrate mixture, proposed by Watanabe and Hirasawa (2018).

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.

Based on the idea that eutectic formation is an useful technology for controlling the melting points of latent heat storage materials over a wide temperature range, precise experimental studies were carried out on the inevitability of eutectic composition of salt hydrate mixtures. Phase diagrams were developed from heating curves of two pseudo-binary systems, Ni(NO3)2·6H2O-CoCl2·6H2O and NiCl2·6H2O-Co(NO3)2·6H2O. The melting points of individual hydrates were 53.5, 53.0, 51.5 and 53.5°C, respectively. In the two binary systems, similar simple eutectic formations were recognized under the same conditions of 30°C and equimolar composition. The crystal compositions in the systems changed depending on the binary mixing ratio. At the same time, new crystal phases that were not attributed to either of original salt hexahydrates were also generated, and the contents of the new phases became maximum at the eutectic points. The two eutectics generated were found to have the same crystal composition as each other as analyzed by X-ray powder diffraction patterns. Consequently, it was concluded that the eutectics were formed through the mutually equivalent exchange of dissociated ions. Further, the inevitability of those compositions was determined as the mixing ratio at which the mutually equivalent exchange might be maintained for all dissociated ions.

The effect of salt addition on the supercooling properties of erythritol was investigated in an attempt to create a novel sugar alcohol type of latent heat storage material that has high thermal storage density and remains in a supercooled state at room temperature. The mechanism of the effect was also examined. Various cationic and anionic species having different valences were each added to erythritol, and their effects on supercooling properties were evaluated with crystallization temperature and supercooling retention time as indices. The supercooling retention mechanism was also investigated focused on the interaction between erythritol and each additive by NMR (Nuclear Magnetic Resonance) spectroscopy. It was found that erythritol additives containing monovalent anions are effective as supercooling stabilizers, and additives containing divalent anions are effective as supercooling inhibitors. It was also found that cationic species have a smaller influence than anionic species. Additives that include the acetate ion were found to be a capable of maintaining erythritol in a supercooled state at room temperature, and the improvement of supercooling retention was considered to be due to the interaction between the hydroxy group of erythritol and the acetate ion.

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.

Sub-10-nm-sized Pt nanoparticles were synthesized by reducing Pt ions with NaBH4, 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.

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.

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.

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.

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.

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.

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.

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 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 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 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.

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.

A new population balance model for solvent-mediated polymorphic transformation is presented. The model takes into account the secondary nucleation caused by nuclei grown crystals as well as the primary nucleation. Numerical simulation was performed for crystallization of a hypothetical enantiotropic dimorphic compound in an unseeded solution. In the simulation, particular attention was paid to the effect of secondary nucleation of the stable polymorph on the transformation time. The simulated transformation time decreased with an increase in the secondary nucleation rate of the stable polymorph. Reported experimental data on the effect of stirrer speed were explained by the secondary nucleation-mediated mechanism, in which the secondary nucleation rate is assumed to increase with an increase in stirrer speed. The effect of scale-up on the transformation time was also suggested to be explained by the secondary nucleation-mediated mechanism.

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.

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.

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.

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.

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.

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 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.

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.

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 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.

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 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 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 purification behavior of uranyl nitrate hexahydrate (UNH) was investigated to evaluate the decontamination performance of liquid and solid impurities using a dissolver solution of mixed oxide (MOX) fuel in batch experiments. The UNH crystal recovered from the MOX fuel dissolver solution containing simulated fission products (FPs) was purified by a sweating and melt filtration process. Although the decontamination factors (DFs) of Pu, Cs, and Ba did not change in the sweating process, that of Eu increased with increases in temperature and time. These results indicate that liquid impurities such as Eu were effectively removed by the sweating method, but solid impurities such as Pu, Cs, and Ba were minimally affected in the batch experiments. On the other hand, the DF of Ba increased with 0.45 and 5.0 mu m filters in the melt filtration process. Since Pu and Cs formed as Cs2Pu(NO3)(6) in the course of U crystallization and was accompanied with the UNH crystal, these behaviors were similar to each other. Although the DFs of Pu and Cs did not change with the 5.0 mu m filter, it increased approximately twofold with the 0.45 mu m filter. The particle size of Cs2Pu(NO3)(6) is relatively small and might pass through the 5.0 mu m filter in the melt filtration process. The liquid impurities as Eu remained in the molten UNH crystal with some filters.

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.

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 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.

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.

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.

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.

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.

Methane fermentation treatment of solids yields a digested sludge containing nitrogen and phosphorus in high concentrations. For the purposes of phosphorus load reduction of the water treatment system, anti-scaling of methane fermentation tanks and their surrounding apparatus, and phosphorus resource recovery, a system for positive crystallization and recovery of magnesium ammonium phosphate (MAP) from the digested sludge was devised. This system consists of a crystallization process, a separation process using the hydrocyclone and a low temperature drying process. The optimum operational conditions for MAP and the MAP drying conditions for a digested sludge containing solids at a concentration of several per cent were clarified, and a pilot-scale plant having a treatment capacity of 2m(3)/h was built and subjected to 16-month demonstration tests.
For the separation of MAP using the hydrocyclone, it is necessary to suppress nucleation in the crystallization process. Based on the laboratory tests, it was found that MAP nucleation is suppressed and the crystal growth becomes predominant when a good fluidized condition of MAP is maintained in the reactor, the reactor is operated at a low supersaturation degree, and a suitable MAP crystallization loading per charged seed crystal amount is maintained. It was also found that, in the drying process, MAP can maintain its form without transition when the drying temperature is set below 70 degrees C. In the demonstration tests of the series of processes, the PO(4)-P removal efficiency in the crystallization process was above 85%, showing that the reactions proceeded well. Moreover, only about 10% of the reacted phosphorus was nucleated; that is, about 90% of reacted phosphorus grew on the seed crystal surfaces, and as a result, MAP could be separated well from the digested sludge. MAP recovered from the drying process had a moisture content below 0.1%, a purity of 92.6%, and a hazardous metal content below the standard values prescribed by the Fertilizer Regulation Act, and therefore, it could be confirmed that MAP has a high quality as a fertilizer product.

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.

Removal and recovery of phosphorous from swage in form of MAP (magnesium ammonium phosphate) have attracted attention from the view point of eutrophication prevention, phosphorus resourcerecovery. In this work, we conducted the basic investigations on the phosphorus recovery process for anaerobic digested sludge using crystallization, and the demonstration tests using a pilot scale and full-scale experimenral plant. A total-phosphorus recovery ratio higher than 30% was achieved, and a reacted soluble phosphorus recovery ratio higher than 95% was achieved. A case study in applying this phosphorus recovery process for treatment of sludge from an anaerobic-aerobic process of 21, 000m³/d sewage plant, evidenced that 30% of phosphorus concentration can be reduced in the final effluent and recovering 315kg/d as MAP.

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.

The effect of ultrasound on nucleation phenomena in the heat storage material Na2HPO4.12H2O was investigated by determining the primary nucleation probability and induction time, and by looking at heat generation phenomena in the initial stage of nucleation. The experimental results show that the primary nucleation probability dramatically increased, and the induction time decreased under the ultrasound irradiation, and in addition, the rate of temperature rise was dependent upon the ultrasonic output. Based on these results and the theoretical relationship between the number of primary nuclei and the heat generation rate, it is proposed that the number of primary nuclei depends upon the ultrasonic output.

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.

Fluoride ion removal by calcium fluoride crystallization was studied. This study aimed to find the range of fluoride ion concentration which would be applicable to calcium fluoride crystallization. First, batch experiments without a seed crystal were conducted to obtain the relationship between initial fluoride ion concentration and calcium ion concentration where fluoride ion concentration would begin to decrease in the process of calcium fluoride precipitation.<br>Batch experiments using a seed crystal were then conducted under the same conditions as those without a seed crystal to obtain the relationship between initial fluoride ion concentration and calcium ion concentration where fluoride ion concentration would begin to decrease due to crystallization of calcium fluoride on the seed crystal.<br>Supersolubility curves of calcium fluoride were obtained from both sets of experiments. From these, the metastable region of calcium fluoride between the solubility curve and the supersolubility curve was obtained. The range of fluoride ion concentration applicable to calcium fluoride crystallization was found to be less than 3 mmol/l.<br>XRD of the grown calcium fluoride crystals was investigated. The main peaks of the calcium fluoride used in the experiments were found to agree with the literature values.

The influence of a surfactant over water on the polymorphism and crystal size of calcium carbonate produced by reaction crystallization in microemulsion systems was investigated in a mixing tank reactor. The crystallization was induced by the reaction between two aqueous micelle solutions (Na2CO3-CaCl2) stabilized by anionic surfactants, SDS (sodium dodecyl sulfate) or AOT (sodium bis(2-ethylhexyl) sulfosuccinate). With increasing surfactant ratio to water, the water-in-oil microemulsion was stably developed and the morphology of the calcium carbonate crystallized in the micelles sharply transformed from calcite to vaterite. The influence of SDS on the polymorphism and crystal size of calcium carbonate was much clearer than that of AOT. In addition, with AOT, certain step changes in the morphology and crystal size occurred around a surfactant ratio to water (R=[H2O]/[surfactant]) of 15 due to a two-phase separation of the microemulsion.

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.

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, 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.

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.

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.

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.

Sanitary landfill leachate softening processes have been developed for scaling problems. Calcium carbonate crystallization characteristics were studied by using the apparatus of fluidizedbed type reactor, with the existence of seeds (blast furnace slag) . Caustic soda and sodium hydrogencarbonates were used for softening. The concentration of calcium in synthetic leachate was adjusted from 1.2 to 14.1 mol⋅ m^-3. The crystallization proceeded rapidly. At the first sampling point (0.1 m), the concentration of calcium had already been reduced from its influent value to effluent value. The calcium removal rate reached was 48%-60%. The turbidity of effluent was under 30, and its pH value was 7.6 8.0. The contents of the fluidized-bed are thoroughly mixed. This reaction can be described by the following equation :<BR>Co-C=Ko⋅C⋅θ<BR>where Co: influent of Ca2+ [mol⋅m-3] C: effluent of Ca²⁺ [mol⋅ m^-3] θ: retention time [h]<BR>Ko: reaction rate constant [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.