Film control and membrane control in charged membranes

Abstract

In ionic transport through charged membranes the two unstirred layers of finite thickness adhering to both membrane surfaces exert some effects on the transport process. While the two limiting cases of complete film-diffusion control and complete membrane-diffusion control are well known, in a great number of cases transport is partially controlled by both the membrane and the unstirred layers. In this paper, the effect of the unstirred layers on the membrane potential in the case of a ternary electrolyte system in a typical concentration cell, is analysed theoretically. For this purpose, a numerical solution to the Nernst-Planck/Poisson/Donnan equation system is proposed. This numerical procedure does not involve any limitation regarding the number of ions nor of the nature of the steady-state transport (diffusion, convection or electric conduction).