Simplified flux equation for transport across ion exchange membranes

A simplified flux equation is used successfully to describe a particular Donnan dialysis process: Na** plus ions are exchanged for Ca** plus ** plus across a Nafion membrane, with Cl** minus as the excluded co-ion. The simplified flux equation is readily integrated to obtain an analytical expression for an effective permeability coefficient which is relatively insensitive to the value chosen for the fixed-charge concentration. A Wilson plot of data obtained at several strip-solution velocities is used to make a first order correction for boundary layer effects.