Polyaniline modified organic–inorganic hybrid cation-exchange membranes for the separation of monovalent and multivalent ions Original Research Article

Organic–inorganic hybrid cation-exchange membranes (CEMs) were chemically modified by in situ polymerization of aniline in acidic medium using FeCl3 as an oxidizing agent. The presence of polyaniline (PANI) on the surface and inside membrane matrix was confirmed from PANI coating density and scanning electron microscopy. Membranes were characterized in details by estimating water uptake, ion-exchange capacity, fixed ion concentration, counter-ion transport number and membrane conductivity. The values of Na+ transport number across the membranes were unchanged, whereas the values of Zn2 + and Al3 + transport number were decreased after modification with PANI. The dense nature of PANI modified membranes was evaluated through an electro-osmotic study. The selectivity of PANI modified membranes towards Na+, Zn2 + and Al3 + ions was investigated by electrodialysis using single or binary mixture of electrolyte solutions (Na+/Zn2 + and Na+/Al3 +). The current and separation efficiencies of CEM and PANI modified membrane (CEM/PANI-120) for Na+, Zn2 + and Al3 + were determined at varied applied current densities and electrolyte solution feed concentrations. The obtained values of current and separation efficiencies for CEM/PANI-120 membrane suggested the suitability of PANI modified membrane in electrodialysis selective separation of Na+ from the binary mixture (Na+/Zn2 + and Na+/Al3 +) in aqueous solutions.