The separation properties of Nation(R) and sulfonated polyimide (SP) membranes have been compared for the recovery of acids from effluents containing metallic salts. To improve the selectivity, we have deposited a polyethylene imine (PEI) anion-exchange layer on the membrane surface by using two different techniques, a conventional electrodeposition and the plasma polymerization technique involving an ethylene/ammonia monomers mixture. We have pointed out the efficiency of the latter technique since the transport number of multivalent cations has been decreased by 74 and 54% for the Nafion(R) and the SP membranes, respectively. Plasma modified sulfonated polyimides are therefore good candidates for electrodialysis processes and constitute an alternative to the Nafion(R) membrane. (C) 2003 Elsevier Science B.V. All rights reserved.