Electrochemical separation of magnesium from solutions of magnesium and lithium chloride

In the process of extracting lithium from salt lake brines with high Mg/Li mass ratio, a large amount of crude carbonate products of magnesium will be treated by the method of land stockpiling, which not only occupies much land and affects the environment, but also causes a waste of magnesium resources. In this work, the multi-stage membrane electrolysis process was proposed for the extraction of magnesium and the separation of lithium from brines, and magnesium hydroxide with high purity was directly prepared, which can be used as a flame retardant. According to the experimental results, the concentrations of Mg2+ and Li+ in the anolyte were reduced to 0.026 g/L and 0.15 g/L, respectively, and the Mg/Li mass ratio decreased from 98 to 0.17. Meanwhile, the extraction rate of magnesium (98.86% > 89.97%), current efficiency (86.69% > 80.75%) and product purity of Mg(OH)(2) (99.93% > 99.46%) in multi-stage electrolysis process were higher than those in one-stage electrolysis, while the transfer proportion of lithium (42.31% < 50.00%), magnesium residual concentration (0.03 < 0.16 g/L) and Mg/Li ratio (0.17 < 1.23) in multi-stage electrolysis process were lower than those in one-stage electrolysis. Additionally, the higher separation efficiency and extraction rate of magnesium can be obtained in the two-stage electrolysis with the electrolysis of 8 h.