Nanoporous polyaniline-co-epichlorohydrin (PANI-EPH)-based anion exchange membranes on polypropylene substrates were developed by contra-diffusion. Single and double quaternisation were carried out to tune zeta potential, ion-exchange capacity, water contact angle, and percent of water content. Water permeability of 1-1.85 L m(-2) h(-1) at 50-200 kPa, and Molecular weight cut-off study indicated the pore size of 4.04-5.85 nm radius. Acid-diffusion study in the static mode led to a proton diffusion coefficient (U-H(+)) of 17 x 10(-3) - 20 x 10(-3) mh(-1) and optimum selectivity (S) of 26-32, which were comparable with poly(phenylene oxide), Neosepta, and hydrophilic polyvinyl alcohol (PVA)-based membranes. A very small Fe+3 diffusion coefficient (U-Fe(+3)) of 5 x 10(-4) - 7 x 10(-4) mh(-1) was obtained for the synthetic solution by size and charge-dependent exclusion of Fe +3 ions (hydrated size of about 0.480 nm) in the nanoporous membranes. For the effluent solution obtained from a local bentonite mine, a U-H(+) value of 1.5 x 10(-3) - 3.5 x 10(-3) mh(- )l and U-Fe(+3) value of 2.6 x 10(-3) - 2.9 x 10(-3) mh(-1) were obtained. These membranes exhibited 33%-40% and 19%-40% acid recovery for synthetic and effluent feed solutions, respectively, suggesting potential utility in acidic effluent treatment.