Capillary model of electroosmotic transport of the free solvent through ion-exchange membranes

An equation for calculating the transport number of a free solvent transferred through an ion-exchange membrane using the physicochemical and structural characteristics of the latter and the properties of an equilibrium solution was derived on the basis of the Stern theory of the electric double layer and the concept that represents the ion-exchange membrane as a capillary system. The model calculations showed that modification of the ion-exchange membrane, which decreased the effective pore radius to 2.0-3.5 nm, almost completely suppressed the electroosmotic transport of free water in the membrane system. The experimentally determined tendencies of variation of water electrotransport due to changes in the structural type of membrane and solution concentration agree well with the suggested model description.