GO-anchored imidazolium based cross-linked composite anion exchange membranes for the enhancement in acid recovery via diffusion dialysis

Abstract

To break the “trade-off” limitations regarding the acid reclamation and selectivity of the commercially available anion exchange membranes (AEMs), herein we report the preparation of specially designed 2D material incorporated dense AEMs to achieve high dialysis coefficient (UH+) and high separation factor (S) for separation of inorganic acids from its corresponding metal salt mixture by diffusion dialysis (DD). The composite AEMs were fabricated by incorporating graphene oxide (GO) into N-alkylated polyacrylonitrile-co-polyvinyl imidazole copolymer followed by crosslinking with hydrazine hydrate. The composite membranes exhibit higher hydrophilicity and increases the water uptake of the membranes. The combined effect of the impregnation of GO and the imidazolium ion on the acid recovery performance have been evaluated. The membrane B3 prepared by the quaternization of the copolymer with butyl bromide having 1.5 % (w/w) of GO in the polymer matrix exhibits the highest acid recovery performance with a UH+ and S value of 48 × 10−3 m/h and 87, respectively during the acid reclamation study of 1 M HCl + 0.2 M FeCl2 mixture. It also showed UH+ values of 37.11 × 10−3 m/h and 16.22 × 10−3 m/h for HNO3 and H2SO4 systems, respectively, with their respective salt mixtures. GO provides a well-organized slit like channels which intensifies the migration of H+ and increases the selectivity of the AEMs towards metal cations. We believe this engineering strategy can be employed to fabricate better AEMs for acid recovery (HCl, H2SO4 and HNO3) by DD process.