Crown ether functionalized polysulfone membrane coupling with electric field for Li+selective separation

In order to improve the selective separation performance of the membrane for Li+ and enhance the separation efficiency, a crown ether functionalized polysulfone membrane was prepared in this paper, and the Li+ was separated by electrodialysis process. Chloromethylated polysulfone (CMPSf) was used as the base membrane, 4′-aminobenzo-12-crown-4-ether (AB12C4) was in-situ grafted onto the surface of CMPSf membrane to obtain the PSf-sg-AB12C4 membrane. The chemical structure of the membrane surface was characterized by ATR-FTIR and XPS. The surface and cross-sectional morphologies of the membrane were characterized by FESEM. The PSf-sg-AB12C4 membrane was used for selective separation of Li+ by membrane coupling with electric field. The results show that the CMPSf membranes and the PSf-sg-AB12C4 porous membrane have almost no selective separation performance for Li+, while the PSf-sg-AB12C4 dense membrane can selectively separate Li+. After optimizing the conditions of voltage, ion concentration and solution pH, the separation factor of the PSf-sg-AB12C4 dense membrane for Mg2+ to Li+ is up to 32.6. In addition, the separation factors of coexisting ions such as Na+, K+, Ca2+ to Li+ are all higher than that of Mg2+ to Li+, suggesting that the PSf-sg-AB12C4 dense membrane is a promising material for selective separation of Li+ from brine.