Search

In order to obtain dynamics parameters for the purpose of crystallization process design and modeling of rubidium chloride, it was investigated that crystallization metastable zone width and growth kinetic of rubidium chloride. The turbidity meter was used to detect the metastable zone width of the aqueous solution system under different linear cooling in an isothermal batch cooling experimental device. And the desupersaturation of rubidium chloride solution with time was measured by adding seed crystal to supersaturated solution at a certain temperature. The metastable zone width of the system increase with the increase of saturation temperature, decrease with the increase of stirring rate, and increase with the increase of cooling rate. The nucleation order and nucleation rate constant of rubidium chloride were obtained by the self-consistent equation of metastable zone width. The nucleation order value is less than 3, indicating that it is instantaneous nucleation. The nucleation order and nucleation constant both increase with the increase of saturation temperature, indicating that the nucleation rate increased with the increase of temperature. When the amount of seed added exceeds a certain amount, the supersaturation of the solution decreases rapidly. According to the supersaturation curve, the growth kinetics of rubidium chloride crystal were calculated. And the growth exponent is about 2 in the experimental temperature range. The constant of crystal growth rate increases with the increase of crystallization temperature. [ABSTRACT FROM AUTHOR]

This study investigates the influences of the evaporation temperature and Mg2+ concentration on the crystallization of an ammonium sulfate mother liquor. Specifically, their effects on the solubility, metastable zone width, crystallization amount, average particle size, and coefficient of variation of ammonium sulfate are examined through the laser and evaporation crystallization methods. Results show that solubility increases and the metastable zone width narrows with an increase in the evaporation temperature. At an evaporation temperature of 338.15 K, the controllability of the crystallization process improves and explosive nucleation does not easily occur. In this case, crystals with large average particle sizes, regular morphologies, and high crystallinity are obtained. With an increase in the Mg2+ concentration in the solvent, solubility decreases. The added Mg2+ covers the active nucleation sites, thus hindering the nucleation of ammonium sulfate and widening the metastable zone width. At a Mg2+ concentration of 0.9 g L−1 or higher, Mg2+ covers the active surfaces of the grains. This inhibits normal crystal growth and hinders the nucleation and growth of ammonium sulfate crystals, so the crystallization amount of ammonium sulfate significantly reduces. [ABSTRACT FROM AUTHOR]

Solubility and metastable zone width (MSZW) are the basis for purifying products by crystallization. The effects of two process impurities, sodium isethionate (SI) and sodium N‐(β‐ethyl sulfonic acid) aminoethyl sulfonate (SA), on taurine solubility and MSZW in water under different conditions were studied. Solubility and MSZW were measured by laser transmission method. The results show that the process impurities can increase solubility slightly but increase MSZW significantly. The weak solubilization might be due to the antagonism of salting‐out effect and structural similarity between taurine and impurities. Combining the viscosities and parameters calculated by nucleation models, the reason for the different effects of the two impurities on MSZW was studied. The fitting and experiment results show that the solid–liquid interfacial energy γeff was increased by 9.1% and the viscosity by 5.4% at 303.15 K in the presence of SI (0.12 mol per kilo H2O). Meanwhile, γeff was increased by 90.4% and the viscosity by 10.5% with SA added (0.12 mol per kilo H2O). Changes in thermodynamic factors (solubility, γeff) and kinetic factors (viscosity) caused by impurities contribute to the extension of MSZW. This study expands the understanding of the role of process impurities in taurine crystallization. [ABSTRACT FROM AUTHOR]

Phosphorus (P) recovery by crystallization of vivianite in digester supernatant (DS) was investigated. A high recovery yield (> 90 %) was obtained with vivianite even for DS with low P concentration (74 mg L−1), as opposed to the formation of struvite and hydroxyapatite where the yield was lower than 50–60 %. Various strategies were tested to produce vivianite with large sizes and narrow size distribution, such as a controlled reagent dosing profile, self‐seeded crystallization, and multistage cascade‐seeded crystallization. The obtained results demonstrated that the main challenge in the development of vivianite P recovery is to promote crystal growth and to suppress secondary nucleation of vivianite during the crystallization process. [ABSTRACT FROM AUTHOR]

Scandium is a rare earth element that has been declared a critical raw material by the EU. Its availability is low but the demand for it is increasing. Bauxite residue presents a possible European source. A novel process to extract scandium from the residue incorporates anti-solvent crystallization, which delivers the scandium salt (NH4)3ScF6 that can be calcined to ScF3 for direct use in an aluminum alloy. However, this crystallization process produces small crystals in the single-digit micrometer scale, hindering solid–liquid separation. In order to facilitate the separation, the crystallization process needs to be better understood and controlled. Therefore, nucleation kinetics are investigated by measuring the metastable zone width (MSZW) with an optical endoscope probe inside a 300 mL stirred fed-batch crystallizer with varying operating parameters. To study the influence of mixing on the MSZW, the stirring rate, the antisolvent addition rate, and the dilution of the antisolvent before injection are varied. The latter is proven to widen the MSZW by a multiple. It could be confirmed that mixing times on different scales greatly influence the MSZW and the growth of the crystals in the process. With these results, the boundaries for operating parameters are studied in order to control the crystallization process and thus crystal growth. [ABSTRACT FROM AUTHOR]

• The metastable zone width (MSZW) of vanillyl alcohol in three pure solvents was determined at various temperatures, cooling rates, and agitation speeds using linear cooling crystallization with the laser power method. • The effects of ultrasound and its amplitude on the MSZW of vanillyl alcohol in ethanol solution were investigated. • Three models—the self-consistent Nývlt-like model, the classical 3D nucleation theory model, and the simplified linear integral model based on classical nucleation theory (CNT)—were employed to estimate the nucleation kinetic parameters for vanillyl alcohol in three solvents, based on the measured MSZW. In this study, linear cooling batch crystallization of vanillyl alcohol using a laser power system was carried out to experimentally measure the metastable zone widths of vanillyl alcohol in selected solvents (ethanol, 2-propanol, and methyl cyanide) at various saturated temperatures (40, 50, and 60 °C), cooling rates (0.5, 1, 1.5, and 2 °C/min), and agitation speeds (300, 400 rpm). Besides, the sonocrystallization of vanillyl alcohol in ethanol was conducted for measuring MSZW at a various ultrasonic amplitudes (0 %, 25 %, 50 %, and 100 %) at a fixed temperature of 40 °C, cooling rate of 1 °C/min, and agitation speed of 300 rpm. For all three solvents, the MSZW decreases with saturation temperature, while it increases with cooling rate, and this trend doesn't change for different agitation speeds. Three models—the self-consistent Nývlt-like model, the classical 3D nucleation theory model, and the simplified linear integral model based on classical nucleation theory (CNT)—were employed to estimate the nucleation kinetic parameters for vanillyl alcohol in three solvents. The goodness fit of the models were checked by the coefficient of determination (R-squared). The R-squared values reflected a very good fit between the experimental and predicted values and implied that the models are reliable to estimate nucleation kinetic parameters. Additionally, the interfacial energy between vanillyl alcohol and the solvents was observed to decrease with increasing temperature. Overall, the results indicate that a low nucleation order and low interfacial energy suggest weak solute–solvent interactions, making nucleation easier in the following order: methyl cyanide > ethanol > 2-propanol. [ABSTRACT FROM AUTHOR]

A comprehensive understanding of the effect of structure similar additives on the nucleation and growth of amino acid in aqueous solution is of great significance for the crystallization of L-phenylalanine and industrial production of anhydrous L-phenylalanine. This paper mainly focuses on the influence of L-tyrosine on the crystallization process of L-phenylalanine by investigating the variation and typical phenomenon in solubility, metastable zone width, crystal nucleation and growth process, and crystal morphology. The results show that the existence of L-tyrosine can obviously increase the solubility and narrow the metastable zone of L-phenylalanine thus promote the nucleation process. Meanwhile, L-tyrosine can also selectively inhibit the formation of monohydrate and improve the purity of industry-favored anhydrous L-phenylalanine in the final product. In order to explore the inhibiting effect of L-tyrosine in crystallization process, the molecular configurations in two different crystallization states were simulated by using Molecular Dynamics.The results show that water and L-phenylalanine molecules tend to form anhydrous crystals when the addition proportion of L-tyrosine increases. The theoretical calculations are in good agreement with the experimental data. The conclusions of this paper will provide new ideas and effective controlling approaches for L-phenylalanine crystals' morphology and amino acids' crystallization process. [Display omitted] • Two polymorphs of L-Phenylalanine (monohydrate and anhydrate forms) were prepared and comprehensively identified from both experimental and simulation aspects. • The effects of structure-similar additive (L-Tyrosine) on the solubility, crystal nucleation, growth and polymorphs of L-Phenylalanine were investigated. • Molecular dynamics was used to simulate the molecular motion in the system with different contents of additives. • Due to the proved inhibiting effect of L-Tyrosine, the production of specific crystal form of L-Phenylalanine can be achieved by controlling or adjusting the addition of the structure similar additives. • The conclusions of this paper could provide new ideas and effective controlling approaches for L-phenylalanine crystal's morphology and amino acids' crystallization process. [ABSTRACT FROM AUTHOR]

Scandium is a rare earth element that has been declared a critical raw material by the EU. Its availability is low but the demand for it is increasing. Bauxite residue presents a possible European source. A novel process to extract scandium from the residue incorporates anti-solvent crystallization, which delivers the scandium salt (NH4)3ScF6 that can be calcined to ScF3 for direct use in an aluminum alloy. However, this crystallization process produces small crystals in the single-digit micrometer scale, hindering solid–liquid separation. In order to facilitate the separation, the crystallization process needs to be better understood and controlled. Therefore, nucleation kinetics are investigated by measuring the metastable zone width (MSZW) with an optical endoscope probe inside a 300 mL stirred fed-batch crystallizer with varying operating parameters. To study the influence of mixing on the MSZW, the stirring rate, the antisolvent addition rate, and the dilution of the antisolvent before injection are varied. The latter is proven to widen the MSZW by a multiple. It could be confirmed that mixing times on different scales greatly influence the MSZW and the growth of the crystals in the process. With these results, the boundaries for operating parameters are studied in order to control the crystallization process and thus crystal growth.

• An integral model was developed to determine the nucleation parameters. • A temperature-dependent function of interfacial energy was proposed. • A temperature-dependent pre-exponential factor inversely proportional to the solution viscosity was adopted. • The metastable zone width data of phenacetin in ethanol were analyzed. By incorporating a temperature-dependent function of interfacial energy and a temperature-dependent pre-exponential factor inversely proportional to the solution viscosity, an integral model was developed according to classical nucleation theory to retrieve the nucleation parameters from the metastable zone width (MSZW) data. The developed model was applied to determine the temperature-dependent interfacial energy and pre-exponential factor during the cooling process from the MSZW data for phenacetin in ethanol experimentally measured in this work. For comparison, the interfacial energy and pre-exponential factor for phenacetin in ethanol at various operating temperatures were determined from the induction time data based on the conventional method. The results indicated that the temperature-dependent interfacial energy and pre-exponential factor for phenacetin in ethanol obtained from the MSZW data based on the developed model were consistent with those obtained from the induction time data based on the conventional method. [ABSTRACT FROM AUTHOR]

[Display omitted] • Systematic study of nucleation behaviors of p-CA from induction time and MSZW. • Nucleation process corrected by CNT, self-consistent Nývlt-like and modified Sangwal's models. • Nucleation tendency in different solvents analyzed by nucleation parameters. • Solute-solvent interactions during nucleation simulated by MEPs, HS surface and RDF. The study of nucleation behaviors during crystallization is important for understanding the drug crystallization process. The induction time of p-coumaric acid (p-CA) was measured in four solvents at various levels of supersaturation. The kinetic parameters of nucleation (interfacial energy, critical nucleation radius, and critical Gibbs free energy) were estimated using the classical nucleation theory (CNT). The results showed that the nucleation difficulty of p-CA in the four solvents was in the order of ethyl acetate > acetone > ethanol > methanol. In addition, the metastable zone width (MSZW) of p-CA was determined in four solvents. The nucleation behaviors of p-CA were further expounded using self-consistent Nývlt-like model and modified Sangwal's model. The results were consistent with those of CNT. To further reveal the impact of interactions between solvent and solute molecules on the nucleation behaviors of p-CA, molecular electrostatic potential surfaces (MEPs), Hirshfeld Surfaces (HS), and the radial distribution function (RDF) were performed. The investigation revealed that the intensity of solvent–solute interactions depended primarily on the strength of hydrogen bonding interactions. The RDF results showed that the magnitude of hydrogen bonding interactions of p-CA in the four solvents was in the following order: ethyl acetate > acetone > ethanol > methanol. As the hydrogen bonding interactions between p-CA and solvent molecules became stronger, the dissociation of solute molecules from solvent molecules became more difficult, leading to a wider MSZW and a lower nucleation rate. [ABSTRACT FROM AUTHOR]

The metastable zone width (MSZW) for the acetylsalicylic acid‐ethanol system was determined by the polythermal method. Nucleation parameters were calculated applying the self‐consistent Nyvlt‐like approach and the classical three‐dimensional theory approach. The results showed the usual increments in MSZW with increases in the cooling rate, mixed effects when raising the agitation rates, and an unusual behavior that reduced MSZW when the saturation temperature decreased. The apparent nucleation order proved to be independent of all three analyzed variables. The interfacial energy increased with higher saturation temperature and activation energies incremented when agitation rates raised. In general, the two approaches explained closely the experimental results. [ABSTRACT FROM AUTHOR]

A linearized integral model based on classical nucleation theory is applied in this work to determine the interfacial energy and pre-exponential factor using a linear plot from the cumulative distributions of the metastable zone width (MSZW) data for some systems reported in the literature, including isonicotinamide, butyl paraben, dicyandiamide, and salicylic acid. Based on the same criterion for the nucleation point, the interfacial energy and pre-exponential factor are determined using the conventional linear regression method from the cumulative distributions of the induction time data for the same systems. The results indicate that the interfacial energy and pre-exponential factor calculated from the MSZW data are consistent with those calculated from the induction time for the studied systems. [ABSTRACT FROM AUTHOR]

The complexity of boron species in aqueous solution becomes the bottleneck in development of boron resources from brine. The concentrations of different boron species and transformation mechanism among boron species are mainly affected with the total boron concentration, temperatures, pH of the solution, and cations in the solution. The change trends for concentration of total boron in the complicated aqueous solution can be obtained with the phase equilibrium results, but the accurate concentration of boron species in the solution cannot be obtained. The metastable zone width (MZW) of borates and H3BO3 changed with the concentrations of impurity ions, the stirring rate, cooling rate, and original temperature for the saturated solution. The Pitzer model is the effective method to calculate the concentration of boron species. More thermodynamic data at temperatures below and above 298.15 K are needed for model parameterization. The main problems existed in the systems containing boron species were summarized, and the future development direction is also discussed. The progresses on boron species in the aqueous solution can provide fundamental data in the comprehensive exploitation of the brine boron resource. [ABSTRACT FROM AUTHOR]

Ammonium alum is an important powder material for producing high purity alumina. It is usually obtained by crystallization from aqueous solution, but impurity ions in solution have a great effect on the quality of final product particles. Effects of sodium, potassium and iron ions on the primary nucleation of ammonium alum were studied by measuring induction time and metastable zone width using focused beam reflectance measurement (FBRM). It was found that potassium ion or iron ion enhanced the nucleation, whereas sodium ion had no obvious effect. Analysis about the mechanism of impurity incorporation showed that, due to the isomorphous substitution, potassium ion or iron ion were easily incorporated into ammonium alum crystals. Moreover, potassium ion was more easily incorporated into crystal than iron ion. Unlabelled Image • Potassium and iron ions promote the nucleation of ammonium alum. • Sodium ion has no significant influence on the nucleation. • Isomorphous substitution leads to the incorporation of potassium and iron ions into crystals. • Potassium ion is more easily built into the crystal than iron ion [ABSTRACT FROM AUTHOR]

The results of an investigation of the effect of Al2(SO4)3 and K2SiO3 impurities on the crystallization of K2SO4 from aqueous solutions are described and discussed. The metastable zone width (MSZW) of K2SO4 aqueous solutions, without and with known concentrations of the impurities, saturated at 40 and 60 °C is determined, using ultrasonic sensor by the controlled solution cooling method at predefined cooling rates R. It is observed that the value of the MSZW of the two types of saturated solutions increases with an increase in the cooling rate R and the concentration Ci of the two impurities. The experimental data of the dependence of MSZW on cooling rate and impurity concentration are analyzed by an approach based on the classical 3D nucleation theory. The results showed that: 1) both impurities suppress the formation of 3D nuclei by physically blocking the active sites on their surfaces, 2) Al2(SO4)3 impurity is more effective than K2SiO3 impurity, and 3) the purity of the K2SO4 crystals is insignificantly affected by these impurities, but the morphology and size of the obtained crystals are influenced strongly by Al2(SO4)3 impurity. [ABSTRACT FROM AUTHOR]

Experimental results of a study of the effect of FeCl3 impurity on the antisolvent crystallization of ammonium dihydrogen phosphate, involving processes of formation of 3D nuclei and growth of these nuclei, from its aqueous solutions saturated at 30 °C and containing different impurity concentrations ci from in situ measurements of temperatures of saturated solutions and pure water as functions of feeding time t of antisolvent ethanol at predefined rates RA are described and discussed. The processes of formation of 3D nuclei and growth of these nuclei are studied in terms of the maximum antisolvent content ΔxmaxN and ΔxmaxG, determined from intervals of temperature difference (Ts−Tw) = ΔT < 0 and ΔT > 0, respectively, obtained from measurements of temperature Ts and Tw of saturated solution, without and with impurity, and pure water. It is found that: 1) the processes of 3D nucleation in antisolvent crystallization from solutions containing impurities can be explained in the framework of theoretical expressions such as a Nývlt‐like relation and an approach based on 3D‐nucleation theory, and 2) adsorption of impurity particles accounts for the increase in the values of antisolvent contents ΔxmaxN and ΔxmaxG of solutions during 3D nucleation and growth of crystallites. [ABSTRACT FROM AUTHOR]

Sodium arsenate, the main component of arsenic‐containing solid waste pollutants, causes serious environmental health threats. Crystallization is one of the effective methods for separating and purifying sodium arsenate from arsenic‐alkali residue lixivium. However, the crystallization process is limited for its low observability and the lack of separation and purification data. In this work, a laser detection system with a magnetic field generator was designed, and the solubility, metastable zone width, interfacial tension, interfacial entropy factor, crystal nucleation, and growth rate of sodium arsenate were investigated in a constant composition environment. The results showed that the solubility, metastable zone width, interfacial tension, and interfacial entropy factor decreases with the presence of a magnetic field. The magnetic field shortened the crystallization induction time and changed the nucleation and growth rate of sodium arsenate. Under the magnetic field, the nucleation rate increased from 2.43 × 1016 to 8.98 × 1017 (s m3)−1, and the growth rate decreased from 4.94 × 10−8 to 2.73 × 10−8 (s m3)−1, the growth mechanism of sodium arsenate as a continuous growth mode was unchanged. In addition, the X‐ray diffraction and infrared showed that the crystal structure of sodium arsenate is unaffected by the magnetic field, indicating that the enhancement of the crystallization process of sodium arsenate with the magnetic field could be a feasible method in engineering application. [ABSTRACT FROM AUTHOR]

A detailed knowledge of the metastable zone width (MSZW) and nucleation kinetics is vital for the design of batch cooling crystallization processes. Factors such as cooling rate and impeller speed affect the MSZW and nucleation kinetics. Crystallization and dissolution temperatures were measured as a function of cooling rate and impeller speed during the batch cooling crystallization of p‐aminobenzoic acid (pABA) from ethanol in a 0.5‐L stirred‐tank crystallizer. The polythermal experimental data were analyzed using the Nyvlt and first principles‐based Kashchiev‐Borissova‐Hammond‐Roberts (KBHR) methods. In all experimental cases, the latter model revealed that the nucleation process of pABA in ethanol was dominated by an instantaneous nucleation mechanism. The Nyvlt and KBHR analyses delivered a range of parameter values associated with a power‐law model describing the nucleation rate as well as the concentration of nuclei. [ABSTRACT FROM AUTHOR]

The transition water activity of azithromycin in water–acetone solvent mixtures at temperatures 293.15 K, 298.15 K, 303.15 K and 308.15 K was determined under atmospheric pressure, and the ternary phase diagrams for the system of water–azithromycin–acetone at varying temperature were described. Results showed that azithromycin monohydrate can be obtained by lowering the water activity and the transition water activity in acetone–water solvent mixtures at temperatures (293.15 K, 298.15 K, 303.15 K and 308.15 K) was 0.17, 0.21, 0.242 and 0.287, which increased with temperature. Besides, the metastable zone width (MSZW) of azithromycin dihydrate in water–acetone solvent mixtures was measured by laser method. The effect of initial temperature and cooling rate on MSZW of azithromycin dihydrate was studied. It was observed that the MSZW decreases with the increase in initial temperature. Nevertheless, the MSZW becomes wider by enhancing the cooling rate. All the results are of great importance to develop a crystallization process for manufacturing azithromycin hydrate and could be helpful to other solvate transformation research. [ABSTRACT FROM AUTHOR]

Measurement methods of metastable zone width (MZW) and nucleation induction time for melting layer crystallization of palm oil (PO) and its olein/stearin (POL/PST) were established, and the effects of cooling rate (corresponding to various supercoolings) on MZWs and induction time for melting layer crystallization of PO, POL, and PST were determined. The results indicated that the MZW coherently rose with increasing cooling rates with respect to PO and POL, while it declined with higher cooling rates for PST. The induction period results demonstrated that the nucleation induction periods of PO, PST, and POL decreased with increasing supercoolings, and the lag time for nucleation negatively correlated to the melting point of oils at the same supercooling. These data could offer significant instruction in designing and controlling the melting layer crystallization process for palm oil. [ABSTRACT FROM AUTHOR]

Cyclopentane (CP) hydrate seeds can lead to nucleation of CH4 hydrate with a lower supersaturation; the concept of nucleation potential was applied to estimate the metastable zone width (MSZW) of CH4 hydrate. To verify the crystal structure of CH4 hydrate formed from the CP hydrate seeds, the hydrate samples were analyzed by high resolution powder diffraction (HRPD). 1 wt% of CP hydrates in the system reduced the MSZW of CH4 hydrate from 3.39 K to 1.32 K, and showed synergetic performance with sodium dodecyl sulfate (SDS). From the hydrate nucleation theory, SDS is able to decrease the effective surface energy for heterogeneous nucleation on the stainless steel wall, but the CP hydrate seeds provide new nucleation sites with even lower surface energy than that of the stainless steel wall. Hence, the nucleation rate depends on the amount of CP hydrate seeds, and the kinetic parameter can be estimated from the concentration of nucleation sites on the CP hydrate seeds. Also, the MSZW of CH4 hydrate was satisfactorily correlated with the amount of CP hydrate seeds by the cumulative nucleation potentials using estimated kinetic parameters. [ABSTRACT FROM AUTHOR]

• The nucleation behavior of tiamulin hydrogen fumarate methanol solvate (THFMS) was investigated. • The solubility and cosolvency effect of THFMS were studied in methanol-ethyl acetate binary mixtures. • The interfacial energy, the critical nucleation potential, and the critical nucleation parameterswere discussed. To investigate the nucleation behavior of tiamulin hydrogen fumarate methanol solvate (THFMS), the solubility, induction time, and metastable zone width (MSZW) of THFMS in methanol-ethyl acetate binary mixtures were measured. The nucleation potential model, which is based on the classical nucleation theory and correlates the induction time and MSZW, has been employed to deal with the experimental data and estimate the interfacial energy and the critical nucleation potential. The estimated values determined from the nucleation potential model are in accordance with the experimental values. The interfacial energy and the critical nucleation potential of THFMS steadily decrease with the increasing saturation temperature, whereas those of THFMS initially decrease and subsequently increase as the ethyl acetate content increases. The results demonstrate that an increase in saturation temperature leads to enhanced nucleation favorability, while the difficulty of nucleation initially decreases and then increases with increasing ethyl acetate content. Furthermore, the critical nucleation parameters, including the critical Gibbs free energy, the critical nucleus size, and the critical number of molecules in a nucleus, exhibit the same trend in alterations regarding both saturation temperature and ethyl acetate content. [ABSTRACT FROM AUTHOR]

• The nucleation behavior and nucleation kinetics of cinnamic acid were investigated and calculated. • Both the solute–solute and solute–solvent interactions during nucleation process were explored by molecular simulation. • The intrinsic mechanism of different solvents affecting the desolvation process was revealed. In this paper, the induction time and the metastable zone widths (MSZWs) of cinnamic acid in four pure solvents methanol, ethanol, acetone, and ethyl acetate were determined. Driven by the same supersaturation, the induction time is ethyl acetate > methanol > ethanol > acetone in descending order, then the effect of solvent on nucleation was further investigated by model fitting and molecular dynamic (MD) simulation. The MSZWs were fitted with the Nývlt's approach and Modified Sangwal's theory to investigate its nucleation kinetics. The results show that the fitted interfacial energy γ increases with decreasing saturation temperature and increasing cooling rate, which explains why nucleation is more likely to occur at high saturation temperatures and low cooling rates. Also, the pre-exponential factor A exhibits a strong correlation with the solvent and cooling rate. Further calculations of the key nucleation parameters (r crit , Δ G crit , J) show a positive relationship between the critical nucleation radius r crit and the critical Gibbs free energy Δ G crit. The nucleation rate J is equilibrated under the combined constraints of saturation temperature and driving force Δ µ. Finally, the intermolecular forces in the lattice were analyzed using Hirshfeld surface (HS) and 2D fingerprinting to probe the self-assembly process of molecules. And the hydrogen bonding sites between solute and solvent were predicted by molecular electrostatic potential surface (MEPs). The solute–solvent interaction was visualized by radial distribution function (RDF) and then quantified by calculating the interaction energy. The results show that the stronger hydrogen bonding interactions lead to lower nucleation rates, revealing the important role of solute–solute and solute–solvent interactions in solute desolvation and nucleation process. [ABSTRACT FROM AUTHOR]

Accurately predicting the metastable zone width is beneficial for controlling the cooling crystallization to increase particle size. In this work, the transformation temperature between anhydrous inositol and dihydrate inositol was determined to be 301.2 K. In industry, only stable anhydrous inositol is required, so the metastable zone width was measured in the temperature range from 308.2 K to 353.2 K. A novel prediction model for metastable zone width was proposed. Cooling rate, stirring linear velocity, saturation temperature and transformation temperature were considered. Fitted with sufficient data, three predictive equations used for different temperature ranges were obtained. The experimental values were in good agreement with the predictive values. Under the guidance of the prediction equations, the particle size and flowability of the obtained anhydrous inositol significantly increased. The results provide guidance for the preparation of large particle inositol and provide reference for the prediction of metastable zone width in other systems. [Display omitted] • The influence of transformation temperature on the MSZW of MI was revealed. • A novel prediction model of MSZW based on Sangwal's self-consistent model was proposed. • The parameters of industrial crystallization are considered in the prediction model. • The prediction model is suitable for both batch and continuous crystallization • The powder flowability of inositol was improved. [ABSTRACT FROM AUTHOR]

Induction time and metastable-zone-width (MSZW) data for aqueous l-glycine solutions in the presence of l-arginine impurity were experimentally measured using a turbidity probe in this study. The nucleation parameters, including the interfacial free energy and pre-exponential nucleation factor, obtained from induction time data, were compared with those obtained from MSZW data. The influences of lag time on the nucleation parameters were examined for the induction time data. The effects of l-arginine impurity concentration on the nucleation parameters based on both the induction time and MSZW data were investigated in detail.

Measurements of the solubility and metastable zone width (MZW) of borax decahydrate in sodium carbonate and sodium hydroxide aqueous were obtained. The onsets of nucleation were detected by the turbidity technique with the temperature range from 285 to 315 K. The results showed that the solubility of borax gradually decreased and the MZW broadened with the mass percentage of sodium carbonate increasing from 0% up to 9.22%. Correspondingly, the solubility and MZW had the same trend with the addition of sodium hydroxide. Meanwhile, the nucleation parameters of borax were determined and analysed to explain the trends obtained. Applying the classical three-dimensional nucleation theory approach, it was found that the addition of carbonate and hydroxide ions led to the values of solid–liquid interfacial energy (γ) increasing, which indicated the CO32− and OH− ions adsorbed on the nuclei but suppressed nucleation rate.

Struvite metastable zone width (MSZW) is important for the operation of struvite crystallizers to recover phosphorus (P) from wastewater streams as large struvite crystals. However, limited information on struvite MSZW is available. In this study, struvite MSZW was determined under 32 different conditions in a continuously stirred struvite crystallizer to systematically examine the influence of various operating parameters on struvite MSZW. It was found that struvite MSZW (1.3–73.1, presented as a supersaturation ratio difference) broadened with increasing pH (7.6–8.6), struvite seed size (0.3–1.7 mm) and addition rate of MgCl2 solution (0.7–4.1 mg Mg min–1), but narrowed with increasing agitation intensity (Reynolds number = 5.4 × 10³–2.3 × 104) and struvite seed mass (0–3.33 g L–1). Based on the results of this study, the supersaturation ratio of struvite in industrial struvite crystallizers should be kept below 10.7 to avoid the intensive formation of fine struvite crystals and the optimal supersaturation ratio is 5.4, under operating conditions similar to those used in this study. When changing the operating parameters of a struvite crystallizer, the resulting change of struvite MSZW should be considered, especially when using the supersaturation ratio as the process controlling parameter. From the MSZW perspective, higher pH, larger addition rate of MgCl2 solution, lower agitation intensity, smaller seed amount or larger struvite seeds enhances the production of large struvite crystals in struvite crystallizers for P recovery from wastewater. [ABSTRACT FROM AUTHOR]

The kinetic rate equation (KRE) model, unlike the population balance equation model, can describe growth, nucleation, and even Ostwald ripening simultaneously. However, the KRE model cannot be applied in cooling crystallization systems. In this work, we propose a modified KRE model to describe cooling crystallization. The modified KRE model can successfully describe crystal growth and nucleation in cooling crystallization systems. In addition, the metastable zone width was simulated using the modified KRE model and compared with the experimental data in references. The results revealed that the modified KRE model could express the effect of overheating prior to cooling on the metastable zone width. As the extent of overheating increases, the metastable zone width becomes wider, which phenomenon can be clearly simulated by the modified KRE model. This modeling capability is attributed to the behavior of particle clusters that are sized less than the size of sub-nuclei. Because the population balance equation model cannot describe the metastable zone width, the modified KRE model has certain competitive advantages in its application to various crystallization systems. [ABSTRACT FROM AUTHOR]

The competition between cocrystallization and separated crystallization in a solvent was explored via X‐ray diffraction and high‐performance liquid chromatography methods in different solvents and by considering the solvent evaporation rate. The results revealed that the solvent system and solvent evaporation rate can affect the nucleation order of the cocrystal and coformers in the solution. In fact, solubility tests in different solvents confirmed that the solubility plays a key role in the cocrystal formation process. Furthermore, the width of the metastable zone influenced the solute nucleation order and was a decisive factor in the cocrystal formation process when the solvent evaporation rate was varied. Cocrystals could therefore be obtained by adjusting the solvents and solvent evaporation rate. The preparation of kinetic 2,4,6,8,10,12‐hexanitrohexaazaisowurtzitane–2,4,6‐trinitrophenol cocrystals via rapid solvent evaporation proves the practicability of this theory. [ABSTRACT FROM AUTHOR]

The solubility, secondary nucleation threshold, and growth kinetics of (RS)-ibuprofen have been studied in an aqueous ethanol solvent. The metastable zone for secondary nucleation is very narrow at lower temperatures in this range, but greatly enlarged at higher temperatures. The crystal growth kinetics not only display significant dispersion of growth rates, but also a dead zone that is dependent on the growth rates of the crystals. Faster growing crystals display almost no dead zone, whereas the smallest crystals have a large dead zone. The size of the dead zone is largely responsible for the dispersion of crystal growth rates, perhaps due to differences in the thermodynamic stability of the different crystals. The mechanism of growth rate dispersion relates to that of the dead zone. [ABSTRACT FROM AUTHOR]

• CO 2 hydrate vapour liquid equilibria in H 2 O/D 2 O were measured. • Shifts > 2 K were observed between H 2 O/D 2 O hydrate equilibrium lines. • MD simulations successfully reproduced the shifts. • Onset nucleation temperatures of CO 2 hydrates in H 2 O/D 2 O were measured. • The nucleation occurs in the vicinity of the temperature of maximum density of H 2 O/D 2 O. In this work, we report the CO 2 hydrate phase equilibria in water (H 2 O), heavy water (D 2 O), and their binary mixtures following the isochoric pressure search method using a rocking cell apparatus. The phase behaviour was mapped within the temperature and pressure range of 276.32 – 284.80 K and 1.59 – 3.78 MPa, respectively. It was found that there is a difference of ∼ 2 K in the equilibrium line of CO 2 hydrates formed in H 2 O and in D 2 O, respectively. The hydrate dissociation enthalpies obtained using the Clausius-Clapeyron equation indicate almost similar values formed either in D 2 O, H 2 O or their mixtures. These shifts in this equilibrium temperature were compared with the triphasic equilibrium temperature variation estimation obtained using Molecular Dynamics Simulations and a very good agreement with the experimentally obtained values was observed. Further, a constant cooling method was used to obtain the onset temperature of hydrate nucleation for these systems at 3.6 MPa. It has been found that during the cooling ramps, the nucleation always occurred in the vicinity of the temperature of maximum density (TMD) of the systems where water still retains some structuredness. The nucleation experiments also give information about the metastable zone width (MSZW) of the studied systems. The results reported in this work indicate the magnitude of the isotopic effect on CO 2 hydrate formation and dissociation that may have implications towards the application of hydrate technology for separation and purification processes. [ABSTRACT FROM AUTHOR]

A linear regression model is presented in this study to determine the pre-exponential factor and interfacial energy of the crystallized substance based on classical nucleation theory using the metastable zone width data. The nucleation event is assumed corresponding to a point at which the total number density of the nuclei has reached a fixed (but unknown) value. One equation is derived for any temperature-dependent functional form of the solubility. Another equation is derived for the van’t Hoff solubility expression. The pre-exponential factor and interfacial energy obtained from these two equations are found consistent for the studied systems, including glutamic acid, glycine, and 3-nito-1,2,4-triazol-5-one. The results obtained from these two equations are also compared with those obtained from the integral method and classical 3D nucleation theory approach.

Abstract The dependence of metastable zone widths (MSZWs) of aspirin in acetic acid and acetic anhydride binary solvent mixture on saturated temperature, cooling rate and solvent composition was experimentally studied by polythermal method. Modified classical nucleation theory approach and modified self-consistent approach which take the saturation temperature and nucleation temperature into consideration were employed to describe the nucleation behavior by correlating the MSZWs with saturated temperature and cooling rate. The critical nucleus size, critical Gibbs energy and solid-liquid interfacial energy were calculated and analyzed. The results suggest that the critical nucleus size as well as the critical Gibbs energy decrease with the increase of supersaturation ratio. The interfacial energy follows linear relationship with molar fraction of acetic anhydride in the mixed solvents. Besides, the nucleation order and the nucleation constant were obtained according to the modified self-consistent approach. The nucleation order is observed to increase with the molar fraction of acetic anhydride in the binary solvents. Highlights • A modified model based on self-consistent approach of Sangwal's theory is proposed. • Nucleation kinetics of aspirin in acetic acid and acetic anhydride binary solvent mixture was estimated. • Metastable zone width and solubility of aspirin in binary solvent mixture was determined. [ABSTRACT FROM AUTHOR]

Abstract: Three approaches for estimation of nucleation rates from induction time and metastable zone width (MSZW) were validated based on directly measured nucleation rates for paracetamol in ethanol. To quantitatively predict nucleation kinetics using Kubota's methods it is necessary to know the minimum detectable number concentration of nuclei. This was found by determination of light transmission of a series of diluted suspensions of newly nucleated crystals where the size had already been assessed by optical reflection measurement (ORM). The measured nucleation rates strongly depended on both temperature and supersaturation. The Nyvlt method predicted nucleation rates in this system reasonably well; however, it gave slightly low estimates for all temperatures. The methods of Kubota provided nucleation rates that were low by an order of magnitude. [ABSTRACT FROM AUTHOR]

The metastable zone width (MSZW) data for aqueous glycine solutions at various saturation temperatures 308–328 K are experimentally measured using the turbidity probe in this work. The integral model based on classical nucleation theory is applied to determine the pre-exponential factor and interfacial energy using the measured MSZW data. It is found that the MSZW data of aqueous glycine solutions are fitted well to the integral model. The results indicate for glycine that the interfacial energy decreases with increasing temperature while the pre-exponential factor increases with increasing temperature. For comparison, self-consistent Nyvlt-like equation and classical 3D nucleation theory approach are also applied to determine the nucleation kinetics of glycine from the measured MSZW data. [ABSTRACT FROM AUTHOR]

The solubility and crystallisability of a range of binary mixtures of n-hexadecane (C 16 H 34 ) and n-octadecane (C 18 H 38 ), as the predominant alkanes present in hydrotreated vegetable oil (HVO), from three representative fuel solutions (dodecane, toluene and kerosene) is presented. The dissolution (saturation) and crystallisation (supersaturation) points of the solutions are measured using poly-thermal methods utilising turbidometric detection over four concentrations from (192 g/l to 400 g/l). The data reveals the existence of more soluble, less stable crystal structures that form from the alkane mixtures, when compared to the stable triclinic crystal structures formed from the single solute component solutions. An increased carbon chain length results in lower solubility for all three solvents and the solvent type is not found to have any significant effect on the solid forms produced from the mixtures. van’t Hoff analysis reveals the solvent type to influence the solute solubility with the closest to ideal behaviour being dodecane followed by kerosene and toluene, respectively. This finding is further supported by the calculated dissolution enthalpies and activity coefficients, which are the lowest in dodecane followed by kerosene and toluene. Larger values of activity coefficients are observed for compositions with molar fraction ( y ) = 0.1, 0.5–0.7 C 18 H 38 which reflect the complex multi-phase formation in the solutions when compared with the more simple binary melt crystallisation system. [ABSTRACT FROM AUTHOR]

The solubilities of ammonium dihydrogen phosphate (MAP) were determined by dynamic method in the systems of (NH 4 ) 2 SO 4 + water and NH 4 F + water at the temperatures of 293.2–343.2 K at an atmospheric pressure, and the experimental data was fitted by the modified Apelblat equation. The result showed that the solubilities of MAP increased with temperature and the adding of the NH 4 F, and decreased with the adding of (NH 4 ) 2 SO 4 within the measurement range. The metastable zone width (MSZW) of MAP was measured by the focused beam reflectance measurement (FBRM) during cooling crystallization process. The effects of the (NH 4 ) 2 SO 4 impurity and NH 4 F impurity on the supercooling temperature ΔT max of MAP were studied. The MSZW of MAP were moved and enlarged by the two kinds of impurities mentioned above with different approaches. [ABSTRACT FROM AUTHOR]

Abstract: Using a spectrophotometer solubility of sucrose in aqueous solutions without and with glucose and fructose additives and their metastable zone width have been investigated. Comparison of our results from pure solutions with those published in the literature shows the reliability of the method. In agreement with the literature the experimental data also show that the impurities decrease the solubility of sucrose in water and the metastable zone width of the solutions. [ABSTRACT FROM AUTHOR]

Abstract: Measurements of temperatures Tw of water at initial temperature 30 °C and temperature Ts of aqueous ADP solutions saturated at 30 °C against the content x of three alcohols (i.e. methanol, ethanol and n‐butanol) added as antisolvents at different rates reveal regions of constant temperature in the maxima of the Tw(x) plots in water and in the vicinity of occurrence of three‐dimensional (3D) nucleation of the Ts(x) plots in the solutions. These regions of constant temperature, represented by the antisolvent content x, lie between x1 and x2 such that Δx = (x2−x1) > 0. It is found that the antisolvent content range Δx decreases with an increase in the maximum constant temperatures in the Tw(x) and Ts(x) plots. From an analysis of the data of x1 and x2 for different maximum temperatures obtained from the Tw(x) and Ts(x) plots it is argued that the maximum value of Δx is related to the withdrawal of the heat of reactions by the cooling system. However, in the case of ADP solutions, the value of Δx representing the width of the maxima due to 3D nucleation in the Ts(x) plots is also related to the reorganization of crystalline clusters to form stable 3D nuclei during antisolvent crystallization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Draw the phase diagram of BAUR-Ⅰ. • Investigate the effects of cooling rates and urea concentrations on MSZWs. • Analyze the nucleation process by the self-consistent Nývlt-like and classical 3D models. • Explore the activation energy of BAUR-Ⅰ. As an intermediate for preparing sedative drugs, barbituric acid (BA) is often used for anesthesia and hypnosis in clinical practice. Due to the poor solubility of BA, barbituric acid – urea co-crystal (BAUR) was prepared to improve the physicochemical properties and bioavailability of BA. Notely, urea is also required in the production process of BA, so selecting urea as the co-crystal former will not bring additional impurities. BAUR has three forms reported. In this paper, the phase diagram of BAUR-Ⅰ was measured to determine the limit concentration of urea. Further, the nucleation metastable zone experiments were conducted to investigate the effects of cooling rates and urea concentrations during the nucleation. The nucleation process was then simulated using two approaches: the self-consistent Nývlt-like approach and the classical 3D model approach. Combined with the calculation of nucleation activation energy E sat , it can conclude that increasing the concentration of urea widens the metastable region to inhibit the nucleation of form Ⅰ in the cooling crystallization. [ABSTRACT FROM AUTHOR]

The metastable zone width (MZW) of lithium metaborate salts at various concentrations was determined using the laser technique. The solubility data for lithium metaborate salts was nearly the same in the presence of NaCl at various concentrations. The MZW of lithium metaborate salts decreased when the stirring rate increased, but increased remarkably with increasing cooling rates and an increasing concentration of sodium chloride. The apparent secondary nucleation order for lithium metaborate salts was obtained using the Nývlt’s approach. The apparent secondary nucleation order m of lithium metaborate salts is 4.00 in a pure LiBO2−H2O system with an improved linear regression method. The m for lithium metaborate salts was enlarged in the system LiBO2−NaCl−H2O.

The metastable zone width of cephradine in a 0.5% sodium bisulfate (W/V) solution was determined at different values of pH and temperatures by using dynamic laser monitoring under atmospheric pressure. As the pH increased, the metastable zone width of cephradine decreased before increasing, with a minimum value at the isoelectric point. The effect of temperature was less pronounced. The induction periods of cephradine in the 0.5% sodium bisulfate (W/V) solution were investigated as a function of the supersaturation ratio. By applying classical homogeneous nucleation theory, we deduced the crystal-liquid interfacial tension and the following fundamental nucleation parameters: the Gibbs free energy change for the formation of the critical nucleus, the radius of the critical nucleus, and the number of molecules in the critical nucleus. [ABSTRACT FROM AUTHOR]