The Influence of the Counterion Nature on the Electroosmotic Transport of Free Solvent through an MK-40 Ion-Exchange Membrane

Abstract

The influence of the counterion nature on the electroosmotic transport of the free solvent through an MK-40 membrane in alkali metal chloride solutions has been experimentally studied. The proportion of free water in the total electroosmotic flux for Li⁺, Na⁺, and K⁺ cations has been evaluated. The experimental data on the electrotransport and physicochemical characteristics of the MK-40 membrane are used to calculate the transport numbers of free water in terms of the capillary model of electroosmotic transport of free water. The electroosmotic permeability depends on the ionic form of the MK-40 membrane due to the changes in the portion of through mesopores inside the membrane. When the concentration of the solution is greater than 1 mol/L, there is almost no free-water transfer across the heterogeneous membrane, and the water transport numbers are determined by the primary hydration numbers of ions in the solution.