Sandwiched liquid-membrane electrodialysis: Lithium selective recovery from salt lake brines with high Mg/Li ratio

A sandwiched liquid-membrane electrodialysis system, which combines the characteristics of liquid-membrane extraction and electrodialysis, has been proposed here to realize the selective extraction of lithium from salt-lake brines with high Mg/Li mass ratio. The sandwiched liquid membrane is comprised of 2 cation exchange membranes and a Li+-loaded organic liquid film. Because of the moderate working environment and satisfactory performance, the TBP + ClO4- system is chosen as the liquid film out of four candidates, namely TBP + FeCl3 system, TBP + ClO4- system, N-butanol, and β-diketone. According to the electrodialysis experiments then, the Mg/Li ratio in catholyte is reduced to lower than 2 from 100 in the initial brine and the specific energy consumption is as low as 0.13 kWh·mol−1 Li. Additionally, the optimal voltage and temperature for the electrodialysis process are determined as 3.00 V and 20 °C. Finally, we also conclude that this approach is highly adaptable to brines with different cation compositions, because of its ability to separate Li+ with other impurity cations in brine (Na+, K+, Mg2+, and Ca2+). With high adaptability and low energy consumption, this sandwiched liquid-membrane electrodialysis system provides a promising perspective for lithium extraction and separation from brines with high Mg/Li ratio.