Electrochemical Lithium Recovery and Magnesium Hydroxide Coproduction from High-Mg 2+ /Li + Salt-Lake Brine

Salt-lake brine accounts for 60% of global lithium reserves, but its high Mg 2+ /Li + ratio (>6) hinders selective lithium recovery. Herein, a novel two-stage electrochemical process integrating a membrane-free single-compartment (SC) Mg 2+ /Li + separator and a membrane-assisted three-compartment (TC) Li + crystallizer was developed for Li 2 CO 3 synthesis. Anodic product extraction enabled in situ OH – accumulation, realizing Mg 2+ precipitation as Mg(OH) 2 without chemical addition. The Li + -enriched brine was converted to battery-grade Li 2 CO 3 via electrolytic conversion of HCO 3 – to CO 3 2– . The process achieved >99.98% Mg 2+ rejection, Li + was enriched to 2.63 times its initial concentration, and 82.99% yield of Li 2 CO 3 (99.6% purity). Pilot-scale tests (1 m 3 ) showed a 75-fold Li + /Mg 2+ ratio increase within 4 h. DFT calculations verified the strong binding of Li + to CO 3 2– (−1.06 eV) and CO 3 2– adsorption on Fe(100) (−7.34 eV), supporting Li 2 CO 3 nucleation. LCA confirmed lower environmental impacts of SC-TC than conventional nanofiltration, with a net profit of US$ 9439.83 per ton of Li 2 CO 3 . The SC-TC process provides a green and scalable route for simultaneous lithium extraction and magnesium valorization from high-Mg 2+ /Li + brines.