Polyaniline-co-epichlorohydrin nanoporous anion exchange membranes for diffusion dialysis

Abstract

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 (UH+) of 17 × 10−3 – 20 × 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 (UFe+3) of 5 × 10−4 – 7 × 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 UH+ value of 1.5 × 10−3 - 3.5 × 10−3 mh−1and UFe+3 value of 2.6 × 10−3 - 2.9 × 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.