Effect of functionality of cross-linker on sulphonated polysulfone cation exchange membranes for electrodialysis

Abstract

Exploring a desirable cross-linker applied in cation exchange membranes (CEMs) to improve dimensional stability as well as electrochemical performance has a great signifcance for the current membrane science and technology. In this investigation, a sequence of crosslinked sulphonated polysulfone (SPSF) CEMs has been prepared to explore the influence of the crosslinking functionality on the dimensional stability and electrodialysis (ED) performance of modified membranes. Different cross-linker structures were obtained according to the cross-linker agent content added during the synthesis route. As expected, the membrane surface became smoother with increasing cross-linker content, presumably as result of the denser structure established. The dimension stability increases according to the crosslinking degree applied, whereas the permselectivity of membranes depends on the conjunction of many important and interlinked factors, including the formation of narrow ion transport channels and the variations in the exchanges sites concentration. It was observed that the optimized CEM (60SPSF-C2#) showed the highest NaCl removal ratio (91.7%) during the desalination experiments and exhibited the higher current efficiency (95.7%) and lowest energy consumption (6.55 kWh kg−1). These results suggest the formation of the optimum three-dimensional network configuration for the membrane structure determined by the functionality of cross-liker selected in this investigation.