It is becoming evident that primary nucleation of crystals of organic molecules from solution is often anything but 'classical' in its complexity. It is also becoming increasingly clear that ...mesoscopic clusters of molecules are at least partly involved in the phenomenon. On-going advances are rapidly enabling these clusters to be investigated with ever more accuracy. However, despite numerous recent studies, fundamental knowledge of the properties, thermodynamics and kinetics of these clusters, and of their role in nucleation, is still limited.
Despite recent advances, fundamental knowledge of the properties, thermodynamics and kinetics of mesoscale clusters, and their role in nucleation, is still limited.
Deep eutectic solvents (DESs) have been proposed as green alternatives for recycling lithium-ion battery (LIB) cathode materials. In the present work, a sustainable DES based on choline chloride and ...L-(+)-tartaric acid has been systematically investigated for leaching of a LIB cathode material (LiCo1/3Ni1/3Mn1/3O2) for the first time. Moreover, in a novel approach, antisolvent crystallization has been applied to recover metals from the DES leachate. The L-(+)-tartaric acid-based DES shows a good leaching capacity and a high leaching rate at 70 °C. Furthermore, antisolvent crystallization is shown to enable a high metal recovery efficiency of cobalt, nickel and manganese (>98.5%). The precipitate from antisolvent crystallization can be used as a precursor for the synthesis of new cathode material, while the remaining DES and antisolvent can be recovered for reuse in the process. This work presents a green, effective and closed-loop metal recovery strategy for recycling LIB cathode materials using a sustainable DES.
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•The solubility of two famotidine polymorphs has been studied in organic solvents.•Melting data and heat capacity of solids and melts have been determined.•Experimental solubility ...data is well-described by various regression models.•The relationship between the polymorphs is confirmed to be monotropic.•The solubility in all solvents is well below ideality.
The present study investigates the solubility of famotidine polymorphs forms A and B between 298.15 K and 348.15 K in a range of pure solvents: water, methanol, ethanol, isopropanol and acetonitrile. Empirical and semi-empirical models have been fitted to solubility data determined experimentally by a gravimetric method. The solid phases have been characterized by FTIR and Raman spectroscopy, SEM and PXRD. In addition, heat capacities and melting data determined by DSC have been used to estimate the fusion thermodynamics and the activity of the solid phases as a function of temperature. The relationship between the famotidine polymorphs is monotropic, with form A being the stable polymorph. For both polymorphs, in terms of mass ratio, the solubility in the studied solvents decreases in the order methanol > water > ethanol > acetonitrile > isopropanol. The activity coefficient at saturation in all the solutions exceeds unity, showing a positive deviation with respect to ideality, which translates into solubilities significantly lower than the ideal values. Among the alcohols, a consistent correlation is observed between the polarity and the order of solubility.The Hildebrand solubility parameter is also well correlated with the order of solubilities in the studied solvents, with a higher solubility in more polar solvents, revealing the importance of the hydrogen bonding of the sulfamoyl group oxygens.
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A new polymorph of the drug active pharmaceutical ingredient piracetam (Form VI) has been discovered and characterized by X-ray powder diffraction (PXRD), solid-state Raman, attenuated total ...reflectance infrared spectroscopy, and differential scanning calorimetry. The PXRD diffractogram of Form VI shows a distinct peak at 24.2° (2θ) that distinguishes it from the previously known polymorphs and solvates. Form VI is metastable with respect to the previously known polymorphs Form II and Form III; in ethanol solution at 288 K, Form VI transforms into Form II within 15 min, while in isopropanol solution Form VI is kinetically stable for at least 6 h. A total of 1200 crystal nucleation induction time experiments of piracetam in ethanol and isopropanol solutions have been conducted, in sets of 40–80 repeat experiments carried out at different temperatures and solute concentrations. Each solution nucleated as a single polymorph, and each set of repeat experiments resulted in different proportions of Form II, Form III, and Form VI, with Form VI dominating at low nucleation temperatures and Form II at higher nucleation temperatures. The induction time data for Form VI at 288 K have been evaluated within the framework of the classical nucleation theory. At equal driving force, nucleation of Form VI is less obstructed in ethanol than in isopropanol, as captured by a lower interfacial energy and higher pre-exponential factor in ethanol. The proportion of Form VI obtained at a comparable driving force increases in the order ethanol < isopropanol.
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This work demonstrates how the thermodynamics of cocrystal formation from the pure, solid coformers can be directly determined from experimentally obtained calorimetric data, without involving ...solubility data or approximations of ideal solution. For the 1:1 cocrystal between the drug API sulfamethazine and salicylic acid, the melting temperatures and associated enthalpies of fusion have been determined for the coformers in their respective pure solid state and as an equimolar physical mixture and for the cocrystal, using differential scanning calorimetry. Heat capacities have been determined for the respective solid forms and their supercooled melts. The Gibbs energy for cocrystal formation and the enthalpic and entropic components have been determined as functions of temperature through a thermodynamic cycle. The Gibbs energy, enthalpy, and entropy of mixing have been estimated from the thermodynamic functions for cocrystal formation and fusion of the solid phases. The results show that the Gibbs energy for cocrystal formation is negative, i.e. the cocrystal is the stable solid phase in relation to a 1:1 mixture of the coformers throughout the temperature interval from room temperature to the cocrystal melting point, and becomes increasingly negative with increasing temperature. Cocrystal formation is an endothermic process, driven by the favorable entropy increase, and is accompanied by a 6% increase in molecular volume. At room temperature, liquid mixing of coformers is found to be weakly exothermic. The results qualitatively align with a previously reported analysis based on solubility data.
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The crystal growth rate of salicylic acid has been determined by seeded isothermal desupersaturation experiments in different organic solvents (methanol, acetone, ethyl acetate, and acetonitrile) and ...at different temperatures (10, 15, 20, and 25 °C). In situ ATR-FTIR spectroscopy and principal component analysis (PCA) were employed for the determination of solution concentration. Activity coefficient ratios are approximately accounted for in the driving force determination. The results show that the dependence of the growth rate on the solvent at equal driving force varies with temperature; e.g., at 25 °C, the growth rate is highest in ethyl acetate and lowest in acetonitrile, while at 15 °C the growth rate is highest in acetonitrile. The growth rate data are further examined within the Burton Cabrera Franck (BCF) and the Birth and Spread (B+S) theories, and the results point to the importance of the surface diffusion step. Interfacial energies determined by fitting the B+S model to the growth rate data are well-correlated to interfacial energies previously determined from primary nucleation data.
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In this work, direct investigation of mesoscale clusters in solution using dynamic light scattering is combined with an indirect method based on the study of primary crystal nucleation and its ...dependence on the conditions of solution preparation and pre-treatment. In a novel approach we have studied how the nucleation induction time of a pharmaceutical cocrystal, a 1 : 1 saccharin-carbamazepine cocrystal, depends on different preparation and pre-treatment conditions, in particular whether solutions are prepared by dissolving the cocrystal solids or the two coformers separately. Nucleation is clearly affected by some pre-treatment conditions, with longer induction times obtained for a high pre-treatment temperature and when solutions are microfiltered after dissolution. The strongest effect was observed when comparing different starting materials, with solutions prepared using cocrystals leading to much shorter induction times than solutions based on the separate coformers. DLS shows that both types of solutions contain mesoscale clusters of the order of 100-300 nm in size, but that there are clear differences in the amount of scattering indicating a higher cluster concentration in the solutions based on cocrystal solids. The results suggest the possibility that mesoscale clusters can have a structural dimension, associated with slow kinetics, which can directly affect nucleation.
Nucleation of a cocrystal from solution shows a dependence on pre-treatment conditions, and on whether solutions are prepared by dissolving the cocrystal solids or the two separate coformers.
•(NH4)3ScF6 solubility decreases with increased NH4F concentration.•(NH4)3ScF6 solubility decreases with increased alcohol concentration.•(NH4)3ScF6 solubility relates to system dielectric constant ...for different alcohols.•(NH4)3ScF6 transforms into NH4ScF4 in water and other phases in low fluoride media.•(NH4)5Sc3F14 is a possible transformation product of (NH4)3ScF6 in 0.5 mol/L NH4F.
This paper investigates the phase equilibria of ammonium scandium fluoride phases in pure water, aqueous NH4F solutions and in mixtures of NH4F and alcohols. The solubility of the solid phases was determined at 25 °C. It was observed that (NH4)3ScF6 transforms into NH4ScF4 when contacted with pure water for 24 h. Solid phase transformation was also noted in NH4F solutions of concentration ≤ 0.5 mol/L. At NH4F concentrations ≥ 0.8 mol/L, no phase change has been observed, and the solubility of (NH4)3ScF6 decreases with increasing NH4F concentration due to the common ion effect. In NH4F-alcohol mixtures, the solubility of (NH4)3ScF6 decreases in the order: methanol > ethanol > 1,3-propane-diol > 2-propanol. This aligns with the decrease in the effective dielectric constant of the resulting solvent mixture, which is very similar for NH4F-alcohol mixtures formed by ethanol and 1,3-propane-diol.
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Salicylamide was used as a model active pharmaceutical compound to investigate the crystal growth process and its associated kinetics. The impact of organic solvent, supersaturation, and temperature ...on the crystal growth was studied. The multiparticle crystal growth kinetics were determined using the seeded isothermal de-supersaturation method and modeled using several growth rate equations, using different representations of the driving force. The results showed that crystal growth is significantly influenced by experimental conditions. Within the range of experimental conditions, the growth kinetics was affected strongly by the temperature and to a lesser degree by solvent choice. Comparison of the growth order parameter reveals a surface integration controlled growth. Higher than expected activation energies indicate desolvation as a governing process. A comparison of the influence of the solvent on the crystal growth of salicylamide against previously published approximate data at much higher supersaturation shows good agreement, but the influence on the interfacial energy is opposite to that observed for crystal nucleation. In a detailed comparison with crystal growth data of salicylic acid, there is a consistency in the influence of the solvent on the crystal growth of the two compounds. Salicylamide growth kinetics is more strongly affected by increasing temperature than salicylic acid.
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In this work, the NRTL-SAC and the Pharma UNIFAC models are evaluated with respect to the capability of prediction of solid–liquid equilibria of pharmaceutical compounds in organic solvents. The ...original NRTL-SAC model is extended through the introduction of temperature-dependent binary interaction parameters, and the two versions of the model are parametrized using vapor–liquid equilibrium (VLE) data. The performance of the NRTL-SAC models for correlation and prediction of the solubility of eight medium-sized flexible pharmaceutical or pharmaceutically similar molecules in multiple pure, organic solvents is examined: risperidone, fenofibrate, fenoxycarb, tolbutamide, meglumine, butyl paraben, butamben, and salicylamide. The performance of the Pharma UNIFAC model is evaluated using data for six of these compounds. In general, it is found that introducing a dependence on temperature to the binary interaction parameters of the NRTL-SAC model can improve its capability for modeling and prediction of the solubility of active pharmaceutical ingredients. For prediction of solubility data the Pharma UNIFAC model generally performs below the two NRTL-SAC models. Averaged over all evaluated systems where the solubility was predicted with each method, values of the root mean squared logarithmic error (RMSLE) in predicted mole fraction solubility obtained for Pharma UNIFAC (30 systems) and for the original and the modified temperature-dependent forms of the NRTL-SAC model (29 systems) are 1.64, 1.17, and 1.09, respectively. Comparing only those systems for which all models were evaluated (18 systems), the RMSLE values are 1.42, 1.06, and 0.87, respectively.
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