INFLUENCE OF THE LAYER FIXED CHARGE-DISTRIBUTION ON THE PERFORMANCE OF AN ION-EXCHANGE MEMBRANE

The effect of different fixed charge distributions on the current effi ciency and electric resistance of an ion-exchange membrane has been in vestigated on the basis of the Donnan model of a membrane including th e polarization layers. It has been found that the studied quantities a lways depend on the current density. For adequately high current densi ties the current efficiency exceeds that for the uniform distribution. The efficiency decreases with the number of distribution units in the membrane and even falls below that for homogeneous distribution. The relation between the efficiency and the sorption does not depend on th e type of fixed charge distribution when the bulk concentrations are t he same. A comparison of two methods for determining the transport num ber of counter-ions has led to the conclusion that the potentiometric (zero-current) method in comparison to the real current conditions cou ld give false results for macroheterogeneous membranes.