Дисертації з теми "Osmotic coefficients"

L’objectif de cette thèse de doctorat est le développement d’une nouvelle méthode théorique basée sur la simulation des équilibres liquide-gaz par simulations de dynamique moléculaire. Cette nouvelle m´méthode prédit les propriétés thermodynamiques telles que l’activité des solvants et les coefficients d’activité des solutés en phases aqueuses et organiques impliquées dans les systèmes d’extraction liquide-liquide. Ces propriétés thermodynamiques sont nécessaires pour les approches de modélisation thermodynamique mésoscopique permettant d’estimer l’efficacité et la s´électivité d’un système d’extraction par solvant jusqu’au une échelle industrielle. Les propriétés thermodynamiques et structurales des solutions électrolytiques aqueuses et des phases organiques, y compris les agrégats résultant des molécules d’extraction des amphiphiles, sont en bon accord avec les données expérimentales et théoriques disponibles. L’approche de dynamique moléculaire de l’équilibre osmotique fournit un nouvel outil puissant permettant d’accéder aux données thermodynamiques
The aim of this PhD thesis is the development of a new theoretical method based on the simulation of vapor-liquid equilibria by means of molecular dynamics (MD) simulation. This new method predicts thermodynamic properties such as solvent activities and solute activity coefficients of aqueous and organic phases used in liquid-liquid extraction systems. These thermodynamic properties are required for mesoscopic thermodynamic modeling approaches estimating the efficiency and selectivity of a given solvent extraction system up to an industrial scale. Thermodynamic and structural properties of aqueous electrolyte solutions and organic solvent phase including aggregates resulting from amphiphilic extractant molecules are reproduced in very good agreement with previously available experimental and theoretical data. The osmotic equilibrium MD approach provides a new and powerful tool for accessing thermodynamic data

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2009.
Includes bibliographical references (leaves 149-152).
The presence of a discriminating barrier separating two solutions differing in concentration generates a net volume flux called osmotic flow. The simple case is of the ideal semi-permeable membrane which completely excludes the solute. The flow through such a membrane is directly proportional to the thermodynamic pressure drop less the osmotic pressure drop. For membranes which partially exclude the solute the osmotic contribution to flow is less than that of the semi-permeable membrane, and the reduction is given by the osmotic reflection coefficient [sigma]o,. This work was motivated by understanding the mechanistic aspects of osmotic flow through such membranes, in order to predict [sigma]o. One of the main goals of the research was to develop computational models to predict [sigma]o for charged porous membranes and charged fibrous membranes. The effects of molecular shape on [sigma]o for rigid macromolecules in porous membranes were analyzed using a hydrodynamic model. In this type of model, employed first by Anderson and Malone, steric exclusion of the solute from the periphery of the pore induces a concentration-dependent drop in pressure near the pore wall, which in turn causes the osmotic flow (Anderson and Malone 1974). Results were obtained for prolate spheroids (axial ratio, [gamma] > 1) and oblate spheroids ([gamma] < 1) in cylindrical and slit pores. Two methods, one of which is novel, were used to compute the transverse pressure variation. Although conceptually different, they yielded very similar results; the merits of each are discussed. For a given value of a/R, where a is the prolate minor semiaxis or oblate major semiaxis and R is the pore radius, [sigma]o, increased monotonically with increasing [gamma]. When expressed as a function of aSEIR, where asE is the Stokes-Einstein radius, the effects of molecular shape were less pronounced, but still significant. The trends for slits were qualitatively similar to those for cylindrical pores. When [sigma]o was plotted as a function of the equilibrium partition coefficient, the results for all axial ratios fell on a single curve for a given pore shape, although the curve for cylindrical pores differed from that for slits. For spheres ([gamma]= 1) in either pore shape, [sigma]o was found to be only slightly smaller than the reflection coefficient for filtration (of). That suggests that [sigma]o can be used to estimate of for spheroids, where results are currently lacking. A computational model was developed to predict the effects of solute and pore charge on [sigma]o, of spherical macromolecules in cylindrical pores. Results were obtained for articles and pores of like charge and fixed surface charge densities, using a theory that combined low Reynolds number hydrodynamics with a continuum, point-charge description of the electrical double layers. In this formulation steric and/or electrostatic exclusion of macromolecules from the vicinity of the pore wall creates radial variations in osmotic pressure. These, in turn, lead to the axial pressure gradient that drives the osmotic flow. Due to the stronger exclusion that results from repulsive electrostatic nteractions, ao, with charge effects always exceeded that for an uncharged system with the same solute and pore size. The effects of charge stemmed almost entirely from particle positions within a pore being energetically unfavorable. It was found that the required potential energy could be computed with sufficient accuracy using the linearized Poisson-Boltzmann equation, high charge densities notwithstanding. In principle, another factor that might influence o in charged pores is the electrical body force due to the streaming potential. However, the streaming potential was shown to have little effect on [sigma]o, even when it markedly reduced the apparent hydraulic permeability. A model based on continuum hydrodynamics and electrostatics was developed to predict the combined effects of molecular charge and size on the o, of a macromolecule in a fibrous membrane, such as a biological hydrogel. The macromolecule was represented as a sphere with a constant surface charge density, and the membrane was assumed to consist of an array of parallel fibers of like charge, also with a constant surface charge density. The flow was assumed to be parallel to the fiber axes. The effects of charge were incorporated into the model by computing the electrostatic free energy for a sphere interacting with an array of fibers. It was shown that this energy could be approximated using a pairwise additivity assumption. Results for [sigma]o, were obtained for two types of negatively charged fibers, one with properties like those of glycosaminoglycan chains, and
(cont.) the other for thicker fibers having a range of charge densities. Using physiologically reasonable fiber spacings and charge densities, [sigma]o, for BSA in either type of fiber array was shown to be much larger than (often double) that for an uncharged system. Given the close correspondence between [sigma]o and the [sigma]f; the results suggest that the negative charge of structures such as the endothelial surface glycocalyx is important in minimizing albumin loss from the circulation.
by Gaurav Bhalla.
Ph.D.

Methods of slab-geometry molecular dynamics computer simulation were tested, compared, and applied to the prediction of activity coefficients, interfacial electrochemistry characterization, and ion transport through a model biological channel-membrane structure. The charged-sheets, 2-D Ewald, corrected 3-D Ewald, and corrected particle-particle-particle-mesh (P3M) methods were compared for efficiency and applicability to slab-geometry electrolyte systems with discrete water molecules. The P3M method was preferred for long-range force calculation in the problems of interest and was used throughout. The osmotic molecular dynamics method (OMD) was applied to the prediction of liquid mixture activity coefficients for six binary systems: methanol/n-hexane, n-hexane/n-pentane, methanol/water, chloroform/acetone, n-hexane/chloroform, methanol/ chloroform. OMD requires the establishment of chemical potential equilibrium across a semi-permeable membrane that divides the simulation cell between a pure solvent chamber and a chamber containing a mixture of solvent and solute molecules in order to predict the permeable component activity coefficient at the mixture side composition according to a thermodynamic identity. Chemical potential equilibrium is expedited by periodic adjustment of the mixture side chamber volume in response to the observed solvent flux. The method was validated and shown to be able to predict activity coefficients within the limitations of the simple models used. The electrochemical double layer characteristics for a simple electrolyte with discrete water molecules near a charged electrode were examined as a function of ion concentration, electrode charge, and ion size. The fluid structure and charge buildup near the electrode, the voltage drop across the double layer, and the double layer capacitance were studied and were found to be in reasonable agreement with experimental findings. Applied voltage non-equilibrium molecular dynamics was used to calculate the current-voltage relationship for a model biological pore. Ten 10-nanosecond trajectories were computed in each of 10 different conditions of concentration and applied voltage. The channel-membrane structure was bathed in electrolyte including discrete water molecules so that solvation, entry, and exit effects could be studied. Fluid structure, ion dynamics, channel selectivity, and potential gradients were examined. This work represents the first such channel study that does not neglect the vital contributions of discrete water molecules.

La pomme (Malus Domestica Borkh.), fruit largement répandu dans les pays tempérés est beaucoup consommée. Elle représente une source importante en composés phénoliques. Cette étude s’est intéressée aux polyphénols des tissus du parenchyme. La problématique s’oriente sur les effets de la texture sur la diffusion de ces molécules. L’originalité de l’approche repose sur l’association de la texture, de la pression osmotique et la diffusion des polyphénols. Les méthodes de caractérisations physiques et biochimiques ont permis de mesurer les changements à l´échelle macroscopique et les modifications chimiques qui s’opèrent dans les matrices végétales. Les résultats de l’étude du transfert de matière ont permis de mettre en évidence les différents facteurs pouvant influer sur les valeurs des coefficients de diffusion. La texture, l’épaisseur, la variété du fruit et la pression du milieu diffusant, constituent des facteurs pouvant influencer le transfert de matière. L’étude de l’évolution de composant de la paroi a montré des changements qui s’opèrent au cours de la diffusion. Des analyses microscopiques ont relevé les modifications à l’échelle cellulaire de la diffusion de procyanidines, polyphénols majoritaires et des interactions avec les composants pariétaux
Apple (Malus domestica Borkh. ) fruit widespread in temperate countries, is much consumed.It represents an important source of phenolic compounds. This study was interestedin polyphenol content of apple tissue parenchyma. The problem concerns effects of texturedegradation on the diffusion of polyphenols molecules. The originality of the approach isbased on the combination of texture, osmotic pressure and polyphenol leaching. Physicaland biochemical methods were used to measure changes at macroscopic scale and chemicalchanges occurring in the parenchymateous tissue . The study of mass transfer highlightedvarious factors that may affect apparent coefficient diffusion. The result showed that thedisintegration of texture , thickness, apple variety and osmotic pressure of leaching mediacan influence mass transfer yield. The study of the Cell walls components showed changesthat occur during leaching process. Light microscopic analysis revealed changes at cellularscale, procyanidins the major polyphenols, leaching phenomena and also interactionswith cell walls matrix

Molecular dynamics simulations are an increasingly valuable tool to biochemical researchers: advances in computational power have expanded the range of biomolecules that can be simulated, and parameters describing these interactions are increasingly accurate. Despite substantial progress in force field parameterization, recent simulations of protein molecules using state-of-the-art, fixed-charge force fields revealed that the interactions among and within protein molecules can be too favorable, resulting in unrealistic aggregation or structural collapse of the proteins being simulated. To understand why these protein-protein interactions are so over-stabilized, I first assessed the ability of simulation force fields to represent accurately the interactions of individual amino acids, employing an osmotic pressure simulation apparatus that enabled direct comparison with experiment. Surprisingly, simulations of most of the amino acids resulted in behavior that was in strong agreement with experiment. A number of amino acids, however—notably those that contain hydroxyl groups and those that carry a formal charge—interacted in ways that were clearly inaccurate. Additionally, some commonly-used force fields failed to accurately represent the interactions of amino acids in a consistent manner. By further investigating the interactions of the functional groups of these amino acids, I was able not only to determine some of the root causes of individual amino acid inaccuracies, but also to implement simple modifications that brought the interactions of these small molecules and amino acids in stronger accord with experiment. These studies have highlighted some of the shortcomings in popular simulation force fields, and have proposed useful modifications to address them. Still, there is additional work that must be—and is being—conducted in order to correctly model the interaction behavior of proteins in simulation.

Orientador: Florencia Cecilia Menegalli
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-13T18:52:37Z (GMT). No. of bitstreams: 1 Monnerat_SandraMourao_D.pdf: 2359962 bytes, checksum: 3df7969a948ecae9b1a169de42e7087a (MD5) Previous issue date: 2009
Resumo: No presente trabalho investigou-se a desidratação osmótica de maçãs (variedade Fuji), seguida ou não de secagem convectiva com ar quente. Foram determinados perfis de concentração de água e soluto(s) em amostras de maçãs cortadas ao meio e desidratadas osmoticamente em soluções aquosas binárias (30% e 50% de sacarose, p/p) e solução ternária (50% de sacarose e 10% de cloreto de sódio, m/m), sob agitação vigorosa e temperatura constante (27°C). As amostras imersas na solução osmótica durante 2, 4 e 8 h foram fatiadas a partir da superfície plana exposta. A densidade e os teores de água, açúcares totais e redutores e cloreto de sódio foram determinados em cada fatia. O modelo matemático que descreve o transporte de cada espécie estudada (água, sacarose e cloreto de sódio) se baseia na equação de continuidade e na Lei de Fick e considera o encolhimento do tecido. O modelo foi ajustado aos dados experimentais, através do método implícito de diferenças finitas de Crank-Nicolson para determinar os coeficientes efetivos de difusão como uma função da concentração, utilizando coordenadas materiais e integrando simultaneamente as equações diferenciais de cada componente (água e sacarose ou água, sacarose e cloreto de sódio). Imagens de microscopia ótica de tecidos tratados osmoticamente, previamente pigmentados com o corante vital vermelho neutro, foram obtidas variando-se a concentração das soluções e o tempo de exposição. Os registros fotográficos retratam alterações da estrutura celular, que variam de acordo com a intensidade do processo de desidratação. A secagem convectiva com ar quente foi realizada em amostras de maçãs cortadas ao meio, frescas e previamente tratadas em solução aquosa de sacarose a 50% p/p durante 4 horas (27°C). Os perfis de umidade foram determinados a partir da superfície, após a exposição da face plana das metades das maçãs ao fluxo de ar quente (60°C ) durante 3, 6, 10 e 24 horas de secagem. O modelo matemático que descreve o transporte da água se baseia nas equações de continuidade e na Lei de Fick e considera o encolhimento do tecido e a concentração inicial não homogênea para o tecido previamente tratado. De maneira similar à desidratação osmótica, a difusividade de água na secagem também foi determinada em função da concentração, utilizando-se o método implícito de diferenças finitas de Crank-Nicolson e coordenadas materiais. Obtevese um bom ajuste dos modelos matemáticos aos dados experimentais de desidratação osmótica e de secagem. A ordem de magnitude dos coeficientes obtidos para a desidratação osmótica foi uma ou duas vezes menor que de coeficientes de difusão binários de soluções puras de sacarose e de cloreto de sódio. No caso da secagem, o comportamento da difusividade mostrou dependência significativa com a concentração de água. O tecido fresco apresentou coeficientes superiores aos do tecido pré-tratado osmoticamente além de funcionalidades distintas para diferentes tempos de secagem (inferior e superior a 6 horas). O tecido tratado apresentou um comportamento mais estável da difusividade da água no material e foi descrito por uma única função. Este fato está relacionado com as mudanças estruturais ocorridas durante a secagem, mais severas para o tecido fresco em relação ao tecido tratado
Abstract: In this study it was investigated the osmotic dehydration of apples (Fuji variety) followed or not by convective drying with hot air. Concentration profiles were determined for water and solute(s) in samples of apples cut in half and osmotically dehydrated in binary aqueous solutions (30% and 50% sucrose, w/w) and ternary solution (50% sucrose and 10% sodium chloride, w/w) under vigorous stirring and constant temperature (27°C). The samples immersed in the osmotic solution for 2, 4 and 8 h were sliced from the exposed flat surface. The density and water, total and reducing sugars and sodium chloride contents were determined in each slice. The mathematical model that describes the transport of each species studied (water, sucrose and sodium chloride) is based on the continuity equation and on the of Fick's diffusion law and considers the tissue shrinkage. The model was fitted to experimental data through the finite difference implicit method of Crank-Nicolson, to determine the effective diffusion coefficients as a function of concentration, using material coordinates and integrating simultaneously the differential equations of each component (water and sucrose or water, sucrose and sodium chloride). Light microscopy images of osmotically processed tissues previously pigmented with the vital dye neutral red, were obtained, varying the concentration of solutions and time of exposure. The photographic records show changes in cellular structure, which vary with the intensity of the dehydration process. The convective air drying was carried out on samples of apples cut in half, fresh and treated in aqueous solution of sucrose to 50% w/w for 4 hours (27°C). The moisture profiles were determined from the surface, after exposure of the flat face of half of the apples to the flow of hot air (60 ° C) during 3, 6, 10 and 24 hours of drying. The mathematical model that describes the water transport is based on the continuity equation, the Fick's diffusion law, the tissue shrinkage and the nonhomogeneous initial concentration of the previously treated tissue. Similarly to the osmotic dehydration, the water diffusivity in drying was also determined in terms of concentration, using the finite difference implicit method of Crank-Nicolson and coordinated materials. It was possible to obtained a good fit of mathematical models to experimental data of osmotic dehydration and drying. The order of magnitude of the coefficients obtained for the osmotic dehydration was one or two times lower than diffusion coefficients of pure binary solutions of sucrose and sodium chloride. For drying, the behavior of diffusivity showed significant dependence with the concentration of water. The fresh tissue showed coefficients greater than the osmotically pre-treated tissue than it needs distinct functions for different times of drying (and less than 6 hours). The treated tissue showed a more stable behavior of the water diffusivity in the material and was described by a single function. This fact is related to the structural changes during drying, more severe for the fresh tissue than for the treated tissue
Doutorado
Doutor em Engenharia de Alimentos

L’objectif du présent travail est de définir une procédure expérimentale optimale pour déterminer les propriétés thermodynamiques de solutions aqueuses binaires d'électrolytes forts. Deux expérimentations complémentaires ont été mises en œuvre. D’une part, des mesures de la pression de vapeur de l'eau ont été effectuées afin de déterminer les variations du coefficient osmotique en fonction de la température et de la composition. Pour cela, un dispositif manométrique statique non isotherme a été construit et validé par l'étude du système H2O-NaCl entre 25°C et 100°C. D’autre part, des mesures isothermes de l'enthalpie de dissolution de NaCl solide dans l'eau ont été effectuées à plusieurs températures (24. 4°C, 44. 3°C, 59. 2°C) par calorimétrie de mélange. L’ensemble des résultats a permis de déterminer les lois de variation en fonction de la température des paramètres du modèle de Pitzer. Le système H2O-Na2SO4 a été étudié entre 25°C et 90°C selon le même plan d'expérience et la méthode de traitement des résultats mis au point sur le système H2O-NaCl a été appliquée avec succès

Gegenstand der Arbeit sind Zusammenhänge zwischen physikochemischen Eigenschaften und Funktionen der Exine bei Ausbreitung, Bestäubung und Befruchtung. Dabei bewährte sich der Einsatz der 3-kammrigen Sporopolleninkapseln (Zentralkapsel und Sacci) in der Permeationschromatographie. Sowohl kinetisch bedingte chromatographische Dispersion kleiner Moleküle als auch Konzentrationsänderungen von Zuckern und Dextranmolekülen im Medium wurden zur Bestimmung von Permeabilitätskoeffizienten der Nexine genutzt. Die Wasserabsorptionskapazität von Exinefragmenten und die hydraulische Leitfähigkeit der Nexine wurden anhand von Konzentrationsänderungen ausgeschlossener Dextranmoleküle ermittelt. Das Tectum der saccalen Sexine ist eine Mikrofiltermembran mit scharfer Trenngrenze im Submikrometerbereich; daher werden an den Sacci nur Hydrokolloide mit Stokes''schen Radius über 100 nm (z.B. aus nativem Dextran) ausgeschlossen. Die Nexine ist eine nicht-ideale Umkehrosmose-Membran, die in Zucker- und Salzlösungen hohe Reflexionskoeffizienten zeigt; zusätzlich besitzt sie wenige große Poren, die den Austausch von Zuckern und selbst kleinen Polymermolekülen ermöglichen. Die hydraulische Leitfähigkeit der Nexine liegt im Größenbereich derjenigen von Plasmamembranen (0,39-0,48 µm s-1 MPa-1); die Ergebnisse zeigen, dass die Exine weder die Nährstoffaufnahme des Sporoplasten aus der lokulären Flüssigkeit noch dessen rasche Rehydratation in der Mikropyle behindert. Die Einfaltungen der distalen Nexine (oberhalb der Sacci) und die Omega-Faltung der Exine zwischen den Sacci (Leptom) bieten beim Quellvorgang Schutz vor zu schneller Flächenausdehnung der Plasmamembran. Der Corpus kann mit konzentrierten Elektrolytlösungen beladen werden. Beim anschließenden osmotischen Schwellen in Wasser reißt die Exine, und der Sporoplast wird mit anhaftender Intine ausgeschleudert. Wasser und andere polare Flüssigkeiten adhärieren stärker als hydrophobe Flüssigkeiten an Sporopollenin. Die Sporopolleninmatrix weist eine hohe Feststoffdichte auf, ist wenig quellfähig (0,18 mL g-1 TM) und deformationsstabil. Dies ermöglicht die Pulverbildung beim Trocknen.
Subject of this thesis are relationships between physicochemical properties and functions of the exine concerning propagation, pollination and fecundation. Here the application of the 3-chambered sporopollenin-microcapsules (central capsule and sacci) in permeation chromatography proved of value. Both the kinetically dependent dispersion of small molecules and changes in concentration of sugars and dextran molecules in the medium were analysed to determine permeability coefficients of the nexine. The water absorption capacity of exine fragments and the hydraulic conductance of the nexine were calculated by means of changes in concentrations of excluded dextran molecules. The tectum of the saccal sexine is a microfiltration membrane with a sharp cut off in the submicrometer range; thus hydrocolloids with Stokes´radii over 100 nm (e.g. from native dextran) are excluded from the sacci. The nexine is a non-ideal reverse osmosis membrane having high reflexion coefficients in sugar and salt solutions; in addition few large pores allow the exchange of sugars and even of small polymers. The hydraulic conductance of the nexine is in the range typically for plasmamembranes (0.39-0.48 µm s-1 MPa-1); the results indicate that the exine does neither obstruct the uptake of nutrients by the sporoplast from the locular fluid nor hinder the rapid rehydration in the micropyle. When rehydrating, the distal foldings of the nexine (above the sacci) and the omega-like folding of the exine between the sacci (leptom), provide protection for the plasmamembrane when its surface area has to increase too rapidly. The corpus can be loaded with a concentrated electrolyte solution. When subsequently transferred into water the exine rupture and the sporoplast along with the intact intine is ejected. Water and other polar liquids adhere stronger to sporopollenin than hydrophobic ones. The matrix of sporopollenin show a high density in its solid content, water absorption capacity is low (0.18 mL g-1 DM) and it is resistant to deformation. This enable the formation of powder while dehydrating.

碩士
國立中央大學
化學工程與材料工程研究所
96
The osmotic pressure Π and virial coefficients ( B2 and B3 ) of linear and star polymers in good solvents are studied by dissipative particle dynamics simulations. The dependence of the osmotic pressure on the concentration c is directly caculated by considering two reservoirs separated by a semi- permeable, fictitious membrane. For linear polymers with chain length N, our simulation results confirm the scaling relations that B2 ~ N3ν in the dilute regime and Π ~ c2.70 in the semi-dilute regime. The exponent is greater than 9/4 due to the nature of soft beads. For star polymers, the scaling relations become B2 ~ Rg3 in dilute regime and Π λcα in semi-dilute regime. Both the prefactor λ and exponent α vary with the arm number but is independent of the arm length. As the arm number is increased, the exponent may rise from 2.7 to 3.07, which is qualitatively consistent with the experimental result.

Thesis (Ph. D.)--University of Alberta, 2010.
Title from pdf file main screen (viewed on Jan. 15, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemical Engineering and Medical Sciences, Departments of Chemical and Materials Engineering and Medical Sciences - Laboratory Medicine and Pathology, University of Alberta. Includes bibliographical references.

Electrolyte solutions play a central role in many processes from industry to biology. Understanding and building predictive models of their properties has therefore been a fundamental goal of physical chemistry from its beginnings. The challenge remains. In this thesis I outline a continuum solvent model of univalent monatomic ions in water. This model calculates the free energy of: 1) a single ion in bulk, 2) of an ion approaching the air–water interface and 3) of two ions approaching each other. Its central advancements are to include quantitatively accurate ionic dispersion interaction energies, missing from classical theories, including the higher order multipole moment contributions to these interactions. It also includes the contribution from the cavity formation energy consistently, including the effect of changes in the cavity’s shape. Lastly, it uses a quantum mechanical treatment of the ions and provides satisfactory values for their size parameters. Because one consistent framework is used with the same assumptions to calculate the free energies in these three different situations the number of parameters can be minimised and the model can be properly tested. These three calculations can be used to reproduce experimental solvation free energies, solvation entropies, partial molar volumes, surface tensions and activity/osmotic coefficients of the alkali-halide electrolyte solutions. A minimum of parameters are used and crucially no salt–specific fitting parameters are necessary. The model is quantitative and predictive and is therefore a satisfactory model of electrolyte solutions. It provides an explanation of several key qualitative puzzles regarding these properties. Namely that ions of the same size can have different solvation energies, that large ions can adsorb to the air–water interface and that ions in solution that have similar solvation energies are more strongly attracted to each other than ions that have dissimilar solvation energies. The continuum solvent model and separate ab initio calculations show that dispersion interactions play a key role in controlling these effects. In particular, dispersion energies explain the attraction of large ions for each other in water and the difference in solvation energy of ions of the same size. The success of the model implies that it is possible to understand the key properties of electrolyte solutions using a continuum solvent model. This is an important conclusion considering the massive computational demands of explicit solvent treatments.

Electrolyte solutions play a central role in life and technological processes because of their complexity. This complexity is yet to be described by a predictive theory of the specific effects that different ions induce in solution. The vast majority of investigations of specific-ion effects have been conducted in aqueous solutions. These studies have revealed that amongst the complexity, the effectiveness of the ions often follow trends that are apparent across a number of very different experiments, revealing an underlying order (e.g. the Hofmeister series). It is often assumed that water itself is intricately involved in these trends. Here I investigate specific-ion effects in non-aqueous solvents rather than water. By extending the investigation to a number of non-aqueous solvents, the role of the solvent in specific-ion effect trends can be elucidated and a better understanding of the general phenomenon gained. Firstly, a more definite terminology is developed for describing the specific-ion effects trends in order to address the current confusion in the literature and provide a basis for the following investigations. An extensive investigation of the scarce literature demonstrates that water is by no means a special solvent with regards to ion-specificity, and that within the complexity there is universality. An investigation of electrostriction under the conditions of infinite dilution shows that the same fundamental specific ion trends are observed across all solvents, demonstrating that ion-specificity arises from the ions themselves. In this regard the influence of solvents, surfaces and real concentrations of electrolytes can be seen as perturbations to this fundamental series. Further work shows that for systems that are perturbed, the trends in non-aqueous protic solvents can be expected to follow the same trend in water; and in aprotic solvents the cations are more likely to adhere to the trend in water than the anions. My experimental work focuses on specific-anion effects of seven Hofmeister sodium salts in the solvents: water, methanol, formamide, dimethyl sulfoxide and propylene carbonate. Two very different experiments were performed; the elution of electrolytes from a size-exclusion chromatography column and an investigation of the electrolyte moderated swelling of a cationic brush (PMETAC) using a Quartz Crystal Microbalance (QCM). The trends observed are consistent across these experiments. A forward or reverse Hofmeister series is observed in practically all salt-solvent combinations, and the reversal is attributed to the polarisability of the solvent. Finally, a qualitative model of ion specific trends is formulated, where the specific-ion effects are fundamentally a property of the ion, and the associated trends correspond to the Hofmeister series for anions and the lyotropic series for cations. When the concentration is increased, or surfaces introduced, the effects of ion-ion interactions and ion-surface interactions can perturb the fundamental series. The perturbation of the series is related to the proticity of the solvent for ion-ion interactions, whereas the polarisability of the solvent and ion are important when a surface is present. This work for the first time individuates the principal properties of the solvent that affect their ordering: proticity and polarisability.