Simultaneous improvement of flux and monovalent selectivity of multilayer polyelectrolyte membranes by ion-imprinting

Abstract

This study aims to fabricate monovalent cations selective membranes through Layer-by-Layer (LbL) assembly with ion-imprinting introduced. Nickel ions (Ni2+) were introduced into the polycation of polyethyleneimine (PEI) as template and then modified the ultrafiltration membrane through LbL assembly followed by glutaraldehyde (GA) crosslinking and reduction. After eluting the template, ion-imprinting channels with specific size were formed in the modified layer. These channels enhanced the water flux with the selectivity for Na+/Mg2+ improved 2.25 times simultaneously compared to the non-imprinted membrane. Besides, the membrane preparation conditions were optimized and the optimum selectivity of 4.16 was achieved. We analyzed the mechanism of improving separation performance via ion-imprinting technology and believed that this environmental-friendly method provides a new road to fabricate monovalent selective membrane for seawater softening and lithium extraction from magnesium-rich brine.