The transport of cadmium and iron through a poly(vinyl chloride)/poly(methyl methacrylate-co-divinyl benzene) carboxylic ion-exchange membrane was investigated with a system containing HCl as the receiver solution and CdCl2 or FeCl3 as the feed solution. Transport of the ions through the membrane depended on the H+ concentration in the receiver solution and the metal concentration in the feed solution. The rate of transfer for cadmium was about 35% higher than that for iron under the same conditions (0.5 mol/dm(3) of HCl, 0.1 mol/dm(3) of CdCl2 or FeCl3, and 5 h of dialysis). (C) 2004 Wiley Periodicals, Inc.