Physical chemistry osmosis

An explanation of the phenomenon of osmosis is provided in most textbooks of physical chemistry. Suppose that a pure solvent and the solvent containing some solute are separated by a membrane that is permeable only for the solvent. In order... 

In further comment, the term osmosis refers to the movement of the solvent phase itself to regions of solute concentration via a semipermeable membrane—that is, a membrane impervious to the salt but not to the solvent. (The effect is to build up an osmotic pressure difference, which may be estimated by methods presented in most physical chemistry texts, and is illustrated in Example 19.1.) This naturally occurring pressure difference must be overcome or reversed in order that the movement of the solvent be from the more solute concentrated region to the less concentrated region—... 

An explanation of the phenomenon of osmosis is provided in most textbooks of physical chemistry. Suppose that a pure solvent and the solvent containing some solute are separated by a membrane that is permeable only for the solvent. In order to obtain pure solvent from the solution by filtering the solute molecules with the membrane, a pressure which is higher than the osmotic pressure of the solution must be applied to the solution side. If the external (total) pressures of the pure solvent and the solution were equal, however, the solvent would move into the solution through the membrane. This would occur because, due to the presence of the solute, the partial vapor pressure (rigorously activity) of the solvent in the solution would be lower than the vapor pressure of pure solvent. The osmotic pressure is the external pressure that must be applied to the solution side to prevent movement of the solvent through the membrane. 

While for a long time individual workers in this field favored a given method of investigation and tended to stress the importance of their results, it is now essential to apply all the available methods simultaneously, and to attaich particular weight to results which confirm and are complementary to one another. While previously in the field of high polymers it was possible to be satisfied with a few, more or less empirical relationships and rules, it appears necessary and possible today to visualize the extension of many of the more exact laws of physical chemistry—vapor pressure, osmosis, viscosity, diffusion, kinetics of reaction, etc.—and thus to incorporate the chemistry of the high polymers securely in the fundamentals of our science. 

The next topic in this chapter, possibly familiar from other physical chemistry courses, is the phenomenon of osmosis and the associated osmotic pressure. This is very important in colloid science. 

What is important to recognize from the discussion is that the boundary condition for mass transfer through a semipermeable membrane is directly analogous to that for a mixed heterogeneous reaction. A consequence of this is that what is said about the one problem can be translated to the other, despite the somewhat different physics and chemistry. The example of reverse osmosis is therefore used as an illustration of a mixed heterogeneous reaction. The major part of the discussion will, however, be confined to the developing layer, where... 

Lemaire T, Moyne C, Stemmelen D. (2007). Modelling of electro-osmosis in clayey materials including pH effects. Physics and Chemistry of the Earth 32(l-7) 441-452. 

Three key elements determine the potential and applications of a hollow-fiber membrane (1) pore size and pore size distribution, (2) selective layer thickness, and (3) inherent properties (chemistry and physics) of the membrane material. Pore size and its distribution usually determine membrane applications, separation factor, or selectivity. The selective layer thickness determines the membrane flux or productivity. Material chemistry and physics govern the intrinsic permselectivity for gas separation and pervaporation, fouling characteristics for RO (reverse osmosis), UF (ultrafiltration), and MF (microfiltration) membranes, chemical resistance for membranes used in harsh environments, protein and drug separation, as well as biocompatibUity for biomedical membranes used in dialysis and biomedical and tissue engineering. 

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