Effects of Operational Parameters on Mg2+/Li+ Separation Performance in Electrodialysis System

Brine with a high magnesium-to-lithium ratio was separated by electrodialysis equipped with a monovalent cation exchange membrane under differing operational parameters. The ionic concentration variations, separation coefficients, lithium recovery ratio, permselectivity coefficient, and Li+ flux were analyzed to evaluate the effect of the initial Li+/Mg2+ mass concentration ratio, applied voltage, and initial volume ratio between the dilute and concentrated compartments on the separation performance of magnesium and lithium. The results showed that the increase in initial Li+/Mg2+ concentration ratio significantly increased the separation coefficient, lithium recovery ratio, and Li+ flux, demonstrating an improvement in the separation performance since the Li+ migration was accelerated when less Mg2+ competed with Li+. As the applied voltage increased from 10 V to 15 V, the separation coefficient increased, and the lithium recovery ratio and Li+ flux increased within 60 min; however, as the applied voltage increased to 20 V, the separation coefficient, the lithium recovery ratio, and the Li+ flux did not increase, which indicated that an increase in the applied voltage within the limits would contribute to the separation performance. The increase in the initial volume ratio between the dilute and concentrated compartments decreased the separation coefficient and lithium recovery ratio, indicating that the separation performance had declined.