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 Mg2+/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 ([email protected]) to separate Li+ from Mg2+ in solution. The effects of pore size sieving and sulfonation of the MOFs on the Li+/Mg2+ separation efficiency were evaluated using the current-voltage (I–V) method, and the stability of the [email protected] 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 Mg2+. Specifically, PVC-based hybrid membrane containing HSO3-UiO-66 shows the highest selectivity for Li+ (Li+/Mg2+ > 4), with the diffusion coefficient of 2.0×10-10 cm2 s-1 for Li+ and 4.67×10-11 cm2 s-1 for Mg2+. This study highlights the stable sulfonated Zr-based MOF with suitable pore sizes for membrane-based Li+/Mg2+ separation, and provides a potential alternative for recovering lithium from salt-lake brines.