At solid-solution interfaces

The recent experimental developments on dark and photoinduced ET reactions give support to the previous speculations on the relevance of these interfaces in such fields as catalysis and solar energy conversion. These disciplines have been, and still are centered on processes at solid solution interfaces. However, particular applications require molecu-larly defined interfaces, where reactants exhibit different solubility properties. In this section, we shall consider some of these systems and the advances reported so far. 

Schindler, P. W. in "Adsorption of Inorganics at Solid/Solution Interfaces" Anderson, M. Rubin, A., Ed. Ann Arbor Science ... 

Hesleitner, P. Babic, D. Kallay, N. Matijevic, E. (1987) Adsorption at solid/solution interfaces. 3. Surface charge and potential of colloidal hematite. Langmuir 3 815-820 Hesleitner, P. Kallay, N. Matijevic, E. (1991) Adsorption at solid/liquid interface. 6. The effect of methanol and ethanol on the ionic equilibrium at the hematite/water interface. Langmuir 7 178-184... 

Kallay, N. Matijevic, F. (1985) Adsorption at solid/solution interfaces. I. Interpretation of surface complexation of oxalic and citric acids with hematite. Langmuir 1 195-201... 

To study the nature and extent of solution adsorption. A small amount of work has been done in studying the interfacial region at solid-solution interface by heat-of-immersion measurements. Few other methods show... 

When transient techniques are employed for fundamental research on these and other subjects, the effect of double-layer charging has to be accounted for in the analysis procedures. It has been observed frequently that at solid—solution interfaces, this process does not obey the capacitive behaviour predicted by double-layer theories. For example, the doublelayer admittance, Fc, cannot be represented by Yc = jciCd, but rather follows the relation [118]... 

Minerals, electrochemistry of — Many minerals, esp. the ore minerals (e.g., metal sulfides, oxides, selenides, arsenides) are either metallic conductors or semiconductors. Because of this they are prone to undergo electrochemical reactions at solid solution interfaces, and many industrially important processes, e.g., mineral leaching and flotation involve electrochemical steps [i-ii]. Electrochemical techniques can be also used in quantitative mineral analysis and phase identification [iii]. Generally, the surface of minerals (and also of glasses) when in contact with solutions can be charged due to ion-transfer processes. Thus mineral surfaces also have a specific point of zero charge depending on their sur-... 

This is particularly important as the physical environment of hybrids at solid/solution interface can differ greatly from that of hybrids formed in bulk solution [13,14],... 

Idealized polyelectrolytes and surfaces are termed mathematical chemicals here. They exist only in the model and in the mind of the modeler. They are used to study and to simulate the effects of the charge and reactivity of solid surfaces and polyelectrolytes, of the pH and ionic strength of the aqueous solution, and of the size (molecular weight, number of monomer units) of the polyelectrolytes on the configurations of polyelectrolytes at solid-solution interfaces and also to suggest the effects of polyelectrolytes on colloidal stability. 

Hkaly, T. W. 1974. Principles of adsorption of organics at solid-solution interfaces. J. Macromol. Sci.-Ckem. A8(3) 603-19. 

Zhang, R., Somasundaran, R, 2006. Advances in adsorption of surfactants and their mixtures at solid/solution interfaces. Advance of Colloid and Interface Science (Adv. Colloid Interface Sci.) 123-126, 213-229. 

Hesleitner, P. et al.. Adsorption at solid/solution interfaces. 3. Surface charge and potential of colloidal hematite, Langmuir, 3, 815, 1987. 

Cohen Stuart MA, Cosgrove T, Vincent B. Experimental aspects of polymer adsorption at solid/solution interfaces. Adv Colloid Interface Sci 1986 24 143-239. 

Many important reactions happen at interfaces. Because reactions between aqueous species and mineral surfaces are so important in low temperature geochemistry, this chapter focuses on reactions at solid/solution interfaces. 

Reaction rates at solid/solution interfaces are controlled by the area of the interface as well as by the chemical and physical conditions that occur there. Surface reactions are approximately confined to a two-dimensional region, so their rates are expressed in terms of how fast species are created per unit of surface area, and this means that the rates have imits of flux (/, mol/m sec). The flux notation (J) and terminology is used throughout this book. The environment at the solid/solution interface is a hybrid of the bulk solid and bulk solution, so models of the chemical and physical conditions controlling the reaction rates must account for this transitional character. Equilibrium thermodynamics provides a powerful starting point for constraining the surface conditions. At equilibrium the chemical potential of each component must be the same throughout the system, so the chemical potential of the components in the surface are equal to their chemical potentials in the solid and solution phases. At low temperatures, the slow rate of equilibration between the bulk solid and the surface may void this requirement for the solid but it should apply for the components in the bulk solution. Also, at equilibrium the principle of detailed balance requires that the rates of forward reactions in the interface must equal the rates of the reverse reactions. In addition, the forward and reverse reaction steps must be the same. Models of reaction rates at equilibrium are well constrained by these principles but as the system departs from equilibrium these requirements fall away and we must search for other principles to model interfacial reaction rates. 

Calorimetric MethoSolid/Solution Interfaces... 

The adsorption of surfactants at solid/solution interfaces has long been the subject of extensive experimental and theoretical research. Various aspects have been addressed, among them the composition and structure of the adsorption layer, the mechanism of the adsorption (different stages), the kinetics, the thermodynamics... 

Chapter 9, by Kiraly (Hungary), attempts to clarify the adsorption of surfactants at solid/solution interfaces by calorimetric methods. The author addresses questions related to the composition and structure of the adsorption layer, the mechanism of the adsorption, the kinetics, the thermodynamics driving forces, the nature of the solid surface and of the surfactant (ionic, nonionic, HLB, CMC), experimental conditions, etc. He describes the calorimetric methods used, to elucidate the description of thermodynamic properties of surfactants at the boundary of solid-liquid interfaces. Isotherm power-compensation calorimetry is an essential method for such measurements. Isoperibolic heat-flux calorimetry is described for the evaluation of adsorption kinetics, DSC is used for the evaluation of enthalpy measurements, and immersion microcalorimetry is recommended for the detection of enthalpic interaction between a bare surface and a solution. Batch sorption, titration sorption, and flow sorption microcalorimetry are also discussed. 

Therefore, an understanding of the conformational behaviour of proteins at solid-solution interfaces is desirable for a variety of reasons. For example, a detailed mapping of conformational changes is necessary for understanding the mechanism of protein adsorption and can help identify optimal conditions to preserve functionality following protein immobilization. Even though major scientific contributions have been made to our understanding of proteins on solid surfaces in recent years... 

Grazing incidence X-ray fluorescence is able to directly determine the surface composition for concentrations ranging from 0.01 M to 1 M under ambient conditions. Coupled with competitive adsorption in mixtnres of salts, this method has the unique ability to distinguish very short-range couplings at the A level. However, it lacks depth sensitivity below abont 5 nm. At solid/solution interfaces, such a sensitivity can be obtained by using the X-ray standing waves technique. 

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