Ion-fractionation of lithium ions from magnesium ions by electrodialysis using monovalent selective ion-exchange membranes

Salt lake brine is an abundant lithium resource and has great developing value and potentiality. But the Mg/Li ratio of some salt lakes in China and Dead Sea in Jordan is extremely high. In this study, electrodialysis (ED) with monovalent selective ion-exchange membranes was used to investigate the separation performance of Li+/Mg2 + from synthetic multinary mixture. The effects of operating conditions on the lithium recovery, permselectivity, and Mg/Li ratio of the product were evaluated. The results indicate that ED with monovalent selective ion-exchange membranes has a significant separation effect on Li+/Mg2 +. When the optimized parameters were used in ED, the Mg/Li mass ratio of the product stream was reduced to 8.0 (18.8 times compared to a feed Mg/Li ratio of 150), and simultaneously, the Li+ recovery reached to 95.3%. Compared to nanofiltration, ED exhibited superiority both technically and economically for the fractionation of Li+/Mg2 +. It was also verified that the presence of co-existing cations would not be detrimental to the feasibility of lithium extraction using ED. Meanwhile, the separation mechanism of ED process was discussed qualitatively.