Separation of H+/Cu2+ cations by electrodialysis using modified proton conducting membranes

The separation properties of Nafion® 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® and the SP membranes, respectively. Plasma modified sulfonated polyimides are therefore good candidates for electrodialysis processes and constitute an alternative to the Nafion® membrane.