PVC-based hybrid membranes containing metal-organic frameworks for Li+/Mg2+ separation

Developing effective technologies for extraction of Li + from salt-lake brines with high Mg 2+ /Li + ratios is paramount for sustainable utilization of lithium resources in electric vehicle and nuclear energy industries. In this work, hybrid membranes were prepared with polyvinyl chloride matrix and six metal−organic frameworks (MOFs@PVC) to separate Li + from Mg 2+ in solution. The effects of pore size sieving and sulfonation of the MOFs on the Li + /Mg 2+ separation efficiency were evaluated using the current-voltage ( I – V ) method, and the stability of the MOFs@PVC membranes was systematically evaluated. The loading amount of MOFs and the thickness of the membranes were also optimized for Li + transport and selectivity. The results show that the small pore size and sulfonation of MOFs are benefit to separate Li + from Mg 2+ . Specifically, PVC-based hybrid membrane containing HSO 3 -UiO-66 shows the highest selectivity for Li + (Li + /Mg 2+  > 4), with the diffusion coefficient of 2.0×10 -10  cm 2  s -1 for Li + and 4.67×10 -11  cm 2  s -1 for Mg 2+ . This study highlights the stable sulfonated Zr-based MOF with suitable pore sizes for membrane-based Li + /Mg 2+ separation, and provides a potential alternative for recovering lithium from salt-lake brines.