Di-quaternized graphene oxide based multi-cationic cross-linked monovalent selective anion exchange membrane for electrodialysis

Abstract

Di-quaternized graphene oxide based multi-cationic cross-linked monovalent selective anion exchange membrane for electrodialysis. • Di-quaternized graphene oxide as a nano cross-linker. • The moderate amount of QGO loading for cross-linked anion exchange membrane. • Cross-linked nanocomposite membranes for monovalent anion separation. • Monovalent selective cross-linked membranes outperform with pristine membrane. A series of monovalent anion selective membranes were synthesized by crosslinking of chloromethylated polysulfone with 1,4-diazabicyclo [2.2.2] octane functionalized graphene oxide (QGO). Cross-linking of QGO provides dense polymer matrix as well as additional functional sites to the membrane. The effect of QGO on physicochemical and electrochemical properties was studied in detail. The best optimized membrane, CrPSf-3 (3 wt% of nano cross-linker) showed 2.01 mmol·g −1 ion exchange capacity, 9.90% swelling ratio, 31.20% water uptake, 72 mS·cm −1 chloride ion conductivity and 0.95 counter ion transport number along with good mechanical and thermal stability. Electrodialysis performance of membrane permselectivity between Cl − and SO 4 2− was studied in mixed salt solution of 0.05 mol·L -1 (NaCl + Na 2 SO 4 ). The CrPSf-3 membrane showed 5.7 separation factor (SF) for Cl − /SO 4 2− which is higher than pristine QPSf (1.7) and commercial FAB-PK-130 membrane (2.01). Furthermore, higher Cl − flux (2.97 mol·m -2 h −1 ) was observed for CrPSf-3 membrane as compare to pristine QPSf (1.45 mol·m -2 h −1 ) and commercial membrane (1.6 mol·m −2 ·h −1 ). To achieve monovalent anion selectivity, effective cross-linking is facile approach to control compactness of the membrane and ion transport channels. Reported cross-linked membrane possesses a potential candidate for water desalination, wastewater treatment, or other monovalent selective separation processes.