Theoretical and Experimental Study of Joint Osmotic and Electroosmotic Water Transfer through a Cation-Exchange Membrane.

Using the previously developed cell model of a charged membrane and the principles of linear thermodynamics of irreversible processes (the Onsager approach), exact and approximate (in the case of an ideally selective membrane) analytical formulae for calculating the osmotic and electroosmotic permeability of the membrane in aqueous solutions of 1:1 electrolyte at constant electric current density and concentration gradient were suggested. The formulae have been successfully verified by our own experimental data for the extrusion cation-exchange membrane MF-4SC p.29 in NaCl solution up to concentrations of 3 M.

Influence of Surface Forces on Membrane Separations.

This Special Issue of , entitled "Influence of Surface Forces on Membrane Separation", is published in honour of Professor Victor Mikhailovich Starov, Doctor of Science in Chemistry, Fellow of the Royal Society of Chemistry [...

Modeling Asymmetry of a Current-Voltage Curve of a Novel MF-4SC/PTMSP Bilayer Membrane.

A novel bilayer cation-exchange membrane-consisting of a thick layer of a pristine perfluorinated membrane MF-4SC (Russian equivalent of Nafion-117) and a thinner layer (1 μm) of the membrane, on a base of glassy polymer of internal microporosity poly(1-trimethylsilyl-1-propyne) (PTMSP)-was prepared and characterized. Using the physicochemical characteristics of one-layer membranes MF-4SC and PTMSP in 0.05 M HCl and NaCl solutions, the asymmetric current-voltage curves (CVC) of the bilayer composite were described with good accuracy up to the overlimiting regime, based on the "fine-porous membrane" model.

Asymmetry of diffusion permeability of bi-layer membranes.

To reveal the reason of asymmetry of the diffusion permeability of bi-layer electrodialysis membranes the following problems have been solved using the model of "homogeneous porous membrane": - diffusion of non-electrolyte solutions across a bi-layer membrane; - diffusion of electrolyte solutions across a non-charged bi-layer membrane; - diffusion of electrolyte solutions across a charged single layer membrane; - diffusion of electrolyte solutions across a charged bi-layer membrane. It is shown that the main factor responsible for the asymmetry is the difference between absolute values of densities of fixed charges (or so called "exchange capacities") of different layers of a membrane under investigation. Only in this case the ratio of the thickness of the membrane layers as well as the ratio of ion diffusivities contributes also to the asymmetry of the diffusion permeability.