No que diz respeito às águas residuais industriais, além da elevada frequência direta de efluentes salinos, o tratamento convencional de efluentes aquosos de diferentes tipos de indústria quase sempre resulta em uma solução contendo sais solúveis e insolúveis que podem ter qualidade suficiente para serem descartados em corpos aquosos, mas qualidade insuficiente para permitir a reutilização da água em processos industriais. Para reutilizar a água, visando o descarte zero de líquido, a cristalização se mostrou tecnicamente viável e tem sido utilizada nesta separação. Simultaneamente com a evaporação da água, os sais dissolvidos tornam-se materiais particulados que são subsequentemente separados por filtração ou centrifugação. Contudo, para atender às necessidades modernas da indústria em relação aos tratamentos com efluentes salinos, o processo de cristalização deve mostrar melhorias, especialmente devido à sua importância para atingir as metas de descarga de líquidos. Neste sentido, a cristalização simultânea representa a possibilidade de remover vários compostos em uma única operação de cristalização a partir de uma solução multicomponente. Isso significa que além da purificação da água, essa operação também pode permitir a recuperação dos compostos nos efluentes, que podem ser considerados como matéria-prima, eliminando resíduos - ou dando-lhes a destinação mais adequada. Para isso, é necessário projetar processos para separar os diferentes componentes que compõem as correntes de efluentes salinos e produzir produtos cristalinos com características morfológicas conhecidas. Dessa forma, o presente trabalho visou investigar o comportamento de sistemas ternários em cristalização, utilizando como modelo o sistema NaCl-KCl-H2O no processo de cristalização evaporativa em batelada, no intuito de avaliar a influência dos parâmetros de processo nos cristais formados e de traçar estratégias que possibilitassem o aproveitamento dos sais contidos nos efluentes. Três diferentes rotas de operação foram testadas para avaliar o comportamento dos cristais: uma inicialmente saturada apenas em NaCl, uma inicialmente saturada apenas em KCl e uma já de início saturada em ambos sais. Diferentes taxas de evaporação, tamanhos e teores de sementes foram testados. Verificou-se, de maneira geral, que o controle de dois fenômenos elementares é a chave para contornar os principais obstáculos desse processo: crescimento epitaxial e nucleação secundária. Em determinadas condições foi possível obter o produto das bateladas em distribuições bimodais, com cada pico rico em um dos sais, com purezas superiores a 90 %. Estes produtos, passíveis de separação simultânea dos cristais por composição e tamanho, foram obtidos em condições de supersaturações mais baixas e semeadura de cristais grandes de KCl e pequenos de NaCl. A partir destes resultados, considerando-se a necessidade de desenvolver técnicas de purificação de água menos intensivas em energia e mais favoráveis ao meio ambiente, um sistema de cristalização por membranas (MC) foi testado, utilizando-se o mesmo sistema modelo. O design proposto para MC possibilitou operar com este sistema por tempos superiores a 6 horas, com decaimento do fluxo em torno de 20 %. Contudo, o produto da cristalização simultânea por membranas não apresentou melhorias quanto à segregação. / In the industrial wastewater treatment, besides high direct frequency of saline effluents, conventional treatment of aqueous effluents of different types of industry usually results in a solution containing soluble and insoluble salts that may be of sufficient quality to be disposed in aqueous bodies, but insufficient quality for water reuse in industrial processes. In order to reuse the water, aiming at zero liquid discharge, crystallization has proved to be technically feasible and has been used in this separation. At the same time, with the evaporation of the water, the dissolved salts become particulate materials which are subsequently separated by filtration or centrifugation. However, to meet the industry\'s modern needs for saline effluent treatments, the crystallization process should show improvements, especially because of its importance in achieving liquid discharge goals. In this sense, simultaneous crystallization represents the possibility of removing several compounds in a single crystallization step from a multicomponent solution. This means that in addition to the purification of the water, this operation can also allow the recovery of the compounds in the effluents. In addition, particulate materials can be considered as raw material, eliminating waste - or disposing the residues appropriately. To this end, research is still needed to design processes to separate the different components that compose saline effluent streams and produce crystalline products with known morphological characteristics. Thus, the present work aimed to investigate the behaviour of ternary systems in crystallization, using as model the NaCl-KCl-H2O system in the batch evaporative crystallization process, in order to evaluate the influence of the process parameters on the crystals formed and to trace strategies to enable the use of the salts contained in the effluents. Three different routes of operation were tested to evaluate the behaviour of the crystals: one initially saturated only in NaCl, one initially saturated only in KCl and one initially saturated in both salts. Different evaporation rates, seed sizes and contents were tested. It was generally verified that control of two elementary phenomena is the key to overcome the main obstacles of this process: epitaxial growth and secondary nucleation. Some experimental conditions enablesd the obtaining of the batch product in bimodal distributions, where each peak was rich in one salt, with purities higher than 90 %. These fractions of the yield, that can be simultaneously separated by composition and size, were achieve mainly at lower supersaturations and using big KCl and small NaCl seeds. From these results, considering the need to develop energy-less and more environmentally friendly water purification techniques, a membrane crystallization (MC) system was tested using the same model system. The proposed design for the MC enable the operation for over 6 hours with a flux decay around 20 %. Yet, the proposed the yield of simultaneous membrane crystallization has not shown improvements in composition segregation.

The primary focus of this work is to develop an understanding of crystallisation in hard sphere systems. The thesis is presented in two parts. The first section is an investigation of the liquid/crystal interface at equilibrium using molecular dynamical simulations. The objective is to understand how the interface might bridge between the disordered and ordered states in liquid/crystal environments. Topological measures of structure are used to investigate whether any precursor structures are present in the liquid phase, close to the interface, that would allow transition from disorder to order. This differs from other work where simpler measures of structure, classifying phases into either liquid or crystal, are used. The results indicate that the liquid/crystal interface of a hard sphere system is very narrow and no readily observable structures were found that extended past the width of the equilibrium interface. The second section of the thesis is a theoretical study of growth kinetics in hard sphere systems using density functional theory. The kinetics in a fixed volume are examined with a single conserved order parameter. The work is extended incorporating both conserved particle and non-conserved structure dynamics. The kinetics of growth are examined and it is shown that the small initial crystals are quickly isolated from the higher pressure of the surrounding system through the development of a depletion zone.

No description available.

No description available.

The primary focus of this work is to develop an understanding of crystallisation in hard sphere systems. The thesis is presented in two parts. The first section is an investigation of the liquid/crystal interface at equilibrium using molecular dynamical simulations. The objective is to understand how the interface might bridge between the disordered and ordered states in liquid/crystal environments. Topological measures of structure are used to investigate whether any precursor structures are present in the liquid phase, close to the interface, that would allow transition from disorder to order. This differs from other work where simpler measures of structure, classifying phases into either liquid or crystal, are used. The results indicate that the liquid/crystal interface of a hard sphere system is very narrow and no readily observable structures were found that extended past the width of the equilibrium interface. The second section of the thesis is a theoretical study of growth kinetics in hard sphere systems using density functional theory. The kinetics in a fixed volume are examined with a single conserved order parameter. The work is extended incorporating both conserved particle and non-conserved structure dynamics. The kinetics of growth are examined and it is shown that the small initial crystals are quickly isolated from the higher pressure of the surrounding system through the development of a depletion zone.

Diphenylalanine (FF) is a dipeptide capable of self-assembly in aqueous solution into needle-like hollow micro- and nanocrystals that possess advantageous properties such as high stiffness and piezoelectricity and have emerged as attractive candidates for functional nanomaterials. In addition, these structures can be made conductive or used as scaffolds for organising functional entities which do not on their own possess a propensity towards self-assembly. At the start of this project, despite wide-ranging interest in the FF assemblies, many important and fundamental aspects of the system remained relatively unexplored. The scope of the present work ranges from nanomaterials science to the relevance of the dipeptide as a model system for the study of aromatic $\pi$-stacking interactions in amyloidogenesis. The basic thermodynamic parameters of FF assembly, the kinetics of that process, and the similarities with, and differences from, the process of fibrillogenesis in polypeptides are explored in detail. The solubility of diphenylalanine in a range of organic solvents and the role of cosolvents in the kinetics of structural assembly were systematically investigated. We find that not only the crystal habit depends on the solvent conditions, but indeed different solvomorphs, possibly differing greatly in mechanical properties, can be obtained from self-assembly in different solvents. The thermodynamics of the dipeptide self-assembly are calculated and placed in the context of earlier work on the free energy of fibril elongation for a range of amyloidogenic polypeptides. It is established that FF aggregation displays the temperature dependence typical of hydrophobic desolvation processes, and that as a model amyloid-forming peptide it displays greater aggregation propensity per amino acid than naturally-occurring polypeptides, due in part to its crystalline as opposed to fibrillar aggregate state. Transition-state measurements are made and the nature of the transition state is elucidated- at the highest-energy point on the aggregation pathway, it is thought that the hydrophobic substituents are still solvent-exposed. The kinetics of self-assembly as a function of solution concentration are quantified through the use of microfluidic techniques, enabling high precision, time-resolved monitoring of the growth process. This work represents the first systematic study of the dependence of the growth rate of diphenylalanine on solution supersaturation. It is found that the aggregation process occurs through established mechanisms of crystal growth. The detailed dependence is shown, and the applicability of the results is demonstrated through the control of the aspect ratio of populations of the assemblies.

No que diz respeito às águas residuais industriais, além da elevada frequência direta de efluentes salinos, o tratamento convencional de efluentes aquosos de diferentes tipos de indústria quase sempre resulta em uma solução contendo sais solúveis e insolúveis que podem ter qualidade suficiente para serem descartados em corpos aquosos, mas qualidade insuficiente para permitir a reutilização da água em processos industriais. Para reutilizar a água, visando o descarte zero de líquido, a cristalização se mostrou tecnicamente viável e tem sido utilizada nesta separação. Simultaneamente com a evaporação da água, os sais dissolvidos tornam-se materiais particulados que são subsequentemente separados por filtração ou centrifugação. Contudo, para atender às necessidades modernas da indústria em relação aos tratamentos com efluentes salinos, o processo de cristalização deve mostrar melhorias, especialmente devido à sua importância para atingir as metas de descarga de líquidos. Neste sentido, a cristalização simultânea representa a possibilidade de remover vários compostos em uma única operação de cristalização a partir de uma solução multicomponente. Isso significa que além da purificação da água, essa operação também pode permitir a recuperação dos compostos nos efluentes, que podem ser considerados como matéria-prima, eliminando resíduos - ou dando-lhes a destinação mais adequada. Para isso, é necessário projetar processos para separar os diferentes componentes que compõem as correntes de efluentes salinos e produzir produtos cristalinos com características morfológicas conhecidas. Dessa forma, o presente trabalho visou investigar o comportamento de sistemas ternários em cristalização, utilizando como modelo o sistema NaCl-KCl-H2O no processo de cristalização evaporativa em batelada, no intuito de avaliar a influência dos parâmetros de processo nos cristais formados e de traçar estratégias que possibilitassem o aproveitamento dos sais contidos nos efluentes. Três diferentes rotas de operação foram testadas para avaliar o comportamento dos cristais: uma inicialmente saturada apenas em NaCl, uma inicialmente saturada apenas em KCl e uma já de início saturada em ambos sais. Diferentes taxas de evaporação, tamanhos e teores de sementes foram testados. Verificou-se, de maneira geral, que o controle de dois fenômenos elementares é a chave para contornar os principais obstáculos desse processo: crescimento epitaxial e nucleação secundária. Em determinadas condições foi possível obter o produto das bateladas em distribuições bimodais, com cada pico rico em um dos sais, com purezas superiores a 90 %. Estes produtos, passíveis de separação simultânea dos cristais por composição e tamanho, foram obtidos em condições de supersaturações mais baixas e semeadura de cristais grandes de KCl e pequenos de NaCl. A partir destes resultados, considerando-se a necessidade de desenvolver técnicas de purificação de água menos intensivas em energia e mais favoráveis ao meio ambiente, um sistema de cristalização por membranas (MC) foi testado, utilizando-se o mesmo sistema modelo. O design proposto para MC possibilitou operar com este sistema por tempos superiores a 6 horas, com decaimento do fluxo em torno de 20 %. Contudo, o produto da cristalização simultânea por membranas não apresentou melhorias quanto à segregação. / In the industrial wastewater treatment, besides high direct frequency of saline effluents, conventional treatment of aqueous effluents of different types of industry usually results in a solution containing soluble and insoluble salts that may be of sufficient quality to be disposed in aqueous bodies, but insufficient quality for water reuse in industrial processes. In order to reuse the water, aiming at zero liquid discharge, crystallization has proved to be technically feasible and has been used in this separation. At the same time, with the evaporation of the water, the dissolved salts become particulate materials which are subsequently separated by filtration or centrifugation. However, to meet the industry\'s modern needs for saline effluent treatments, the crystallization process should show improvements, especially because of its importance in achieving liquid discharge goals. In this sense, simultaneous crystallization represents the possibility of removing several compounds in a single crystallization step from a multicomponent solution. This means that in addition to the purification of the water, this operation can also allow the recovery of the compounds in the effluents. In addition, particulate materials can be considered as raw material, eliminating waste - or disposing the residues appropriately. To this end, research is still needed to design processes to separate the different components that compose saline effluent streams and produce crystalline products with known morphological characteristics. Thus, the present work aimed to investigate the behaviour of ternary systems in crystallization, using as model the NaCl-KCl-H2O system in the batch evaporative crystallization process, in order to evaluate the influence of the process parameters on the crystals formed and to trace strategies to enable the use of the salts contained in the effluents. Three different routes of operation were tested to evaluate the behaviour of the crystals: one initially saturated only in NaCl, one initially saturated only in KCl and one initially saturated in both salts. Different evaporation rates, seed sizes and contents were tested. It was generally verified that control of two elementary phenomena is the key to overcome the main obstacles of this process: epitaxial growth and secondary nucleation. Some experimental conditions enablesd the obtaining of the batch product in bimodal distributions, where each peak was rich in one salt, with purities higher than 90 %. These fractions of the yield, that can be simultaneously separated by composition and size, were achieve mainly at lower supersaturations and using big KCl and small NaCl seeds. From these results, considering the need to develop energy-less and more environmentally friendly water purification techniques, a membrane crystallization (MC) system was tested using the same model system. The proposed design for the MC enable the operation for over 6 hours with a flux decay around 20 %. Yet, the proposed the yield of simultaneous membrane crystallization has not shown improvements in composition segregation.

No description available.

No / Despite a tendency to undergo solution-mediated polymorphic transformation, the dissolution behaviour of the metastable FI (triclinic) polymorph of the pharmaceutical compound carbamazepine (CBZ) was investigated using in situ optical microscopy. Experiments were performed at an undersaturation where single crystals of the metastable FI polymorph dissolved. Dissolution in different solvents was investigated at a constant undersaturation. Separately the sublimation of FI was examined and additionally the dissolution was observed at undersaturations where the more stable FIII polymorph crystallized. The results show that both the dissolution and sublimation of FI occur primarily in the direction of the a-axis of the FI crystal structure where the CBZ molecules are found to stack in this direction. The order for the dissolution rate of FI was acetonitrile ≥ methanol > ethanol. The order of the dissolution rates in each of the solvents is inversely correlated to the viscosity and the binding energy of the solvents with the (100) surface of FI in each of the solvents. This suggests that the rate determining step for the dissolution may be either the diffusion or the detachment of CBZ molecules from the surface of FI. A notable difference in dissolution behaviour is also observed at undersaturations where the more stable FIII polymorph nucleates and grows. / SFI

Yes / Polymorphism, crystal shape and solubility of 1,4-dihydroxyanthraquinone (quinizarin) have been investigated in acetic acid, acetone, acetonitrile, n-butanol and toluene. The solubility of FI and FII from 20 °C to 45 °C has been determined by a gravimetric method. By slow evaporation, pure FI was obtained from n-butanol and toluene, pure FII was obtained from acetone, while either a mixture of the two forms or pure FI was obtained from acetic acid and acetonitrile. Slurry conversion experiments have established an enantiotropic relationship between the two polymorphs and that the commercially available FI is actually a metastable polymorph of quinizarin under ambient conditions. However, in the absence of FII, FI is kinetically stable for many days over the temperature range and in the solvents investigated. FI and FII have been characterized by infrared spectroscopy (IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission and ordinary powder X-ray diffraction (PXRD) at different temperatures. The crystal structure of FII has been determined by single-crystal XRD. DSC and high-temperature PXRD have shown that both FI and FII will transform into a not previously reported high-temperature form (FIII) around 185 °C before this form melts at 200–202 °C. By indexing FIII PXRD data, a triclinic P[1 with combining macron] cell was assigned to FIII. The solubility of quinizarin FI and FII in the pure organic solvents used in the present work is below 2.5% by weight and decreases in the order: toluene, acetone, acetic acid, acetonitrile and n-butanol. The crystal shapes obtained in different solvents range from thin rods to flat plates or very flat leaves, with no clear principal difference observed between FI and FII. / SFI; Swedish Research Council