The construction of an efficient magnesium–lithium separation thin film composite membrane with dual aqueous-phase monomers (PIP and MPD)

A series of thin film composite (TFC) membranes was prepared with piperazine (PIP) and m-phenylenediamine (MPD) in different ratios, and the magnesium–lithium separation performance of TFC membranes in salt-lake brine with the magnesium–lithium ratio of 28 were systematically compared. The prepared TFC membranes exhibited high rejection of magnesium ions and negative rejection of lithium ions with high water flux, enabling high magnesium–lithium separation efficiency. The characterisation using FTIR spectroscopy, XPS, zeta potential measurements, and SEM techniques indicated that the composition and surface morphology of the membrane prepared with dual aqueous monomers were found to be different from those prepared with single aqueous monomers under the similar conditions. The interfacial polymerization process of different monomers and the structure–performance mechanism of TFC membranes were further discussed.