How physico-chemical and surface properties of cation-exchange membrane affect membrane scaling and electroconvective vortices: Influence on performance of electrodialysis with pulsed electric field

Two different lots of cation-exchange membranes (CMX-SB-1 and -2) were compared in terms of physico-chemical and electrochemical properties. Further, electrodialysis with both membrane lots was carried out under pulsed electric field (PEF) on model solution containing Ca2+ and Mg2+ ions. It was found that CMX-SB-1 was more scaled with prevalence of Ca compounds on both membrane sides. CMX-SB-2 contained less scaling with prevalence of Ca compounds on diluate side and Mg compounds on concentrate side. The different behavior of membranes was hypothesized to be due to the differences in their intrinsic structure and surface properties. The CMX-SB-2 has higher concentration of fixed charges and water content, which cause larger size of inner channels and easier transport of Mg2+; the structural organization of CMX-SB-1 with presumably narrower nanochannels leads to the slower Mg2+ migration and their low quantity on CMX-SB-1 concentrate side. Additionally, the surface hydrophobicity and heterogeneity of CMX-SB-2 is higher than that of CMX-SB-1 what allow easier water slip on CMX-SB-2 surface facilitating electroconvection. Thus, more scaled CMX-SB-1 membrane with less developed electroconvection yielded lower values of demineralization (59.0% and 57.2% for 2s/0.5s and 2s/0.67s PEF respectively) than the less scaled CMX-SB-2 with better developed electroconvection (77.3% and 75.2% respectively). •Membrane nanostructure influences scaling composition and structure.•Membrane surface properties have a major role on electroconvection development.•Electroconvective vortices affect the scaling quantity and ED performance.•Pulse lapse duration impacts development of electroconvective vortices.•Pause lapse duration impacts development of inertial vortices.