Preparation of polyamide nanofiltration membrane for Mg2+/Li+ separation via interfacial polymerization assisted by ion-imprinting technology

To achieve a high efficiency separation of Mg 2+ and Li + , it is essential to precisely regulate the membrane's surface charge density and pore size. This work proposed a strategy for fabricating polyamide (PA) layer with ion-imprinted structures via interfacial polymerization (IP) assisted by ion-imprinting technology (IIT). Cu(II) was added to the Polyethyleneimine (PEI) aqueous phase to regulate the structure of PA nanofiltration (NF) membranes. After removal of Cu(II), PA-IIM 0.16 exhibited a selectivity factor of 44.27 for Mg 2+ /Li + mixture (2000 mg L −1 , 120:1). Upon the completion of the initial NF process, the Mg 2+ /Li + mass ratio underwent a significant reduction, dropping from the starting value of 120 to 2.32. This method facilitates the rapid penetration of Li + while preserving the high rejection of Mg 2+ by meticulously modulating the NF layer in terms of its pore size as well as its surface charge.