Electrochemical lithium recovery system through the simultaneous lithium enrichment via sustainable redox reaction

With the drastic increase in the demand for lithium, electrochemical lithium recovery has gained significant attention as an alternative for lime soda evaporation. Despite its high selectivity and efficiency, the industrial application of electrochemical systems remains limited because of its discontinuous operation and the low lithium concentration in the source water. Hence, this study proposes a redox-mediated system for selective lithium recovery in tandem with the continuous enrichment of the source water via a sustainable redox reaction. In the proposed system, the reversible redox reaction of ferri-/ferrocyanide enables continuous enrichment of the source water, while lithium-selective adsorbent (lambda-MnO2) selectively recovers the enriched lithium simultaneously. The redox-mediated lithium recovery system successfully concentrated lithium ions up to 37 mM Li+ in an equimolar mixture of 5 mM Li+ and 5 mM Na+, and up to 0.6 mM Li+ even from extremely dilute lithiumcontaining solutions (0.1 mM Li+: 9.9 mM Na+). With the introduction of lambda-MnO2 as a chemical adsorbent, this system exhibited an exceptional selectivity (selectivity coefficient (alpha Li-Na) of 57) toward lithium from an equimolar mixture, and high lithium selectivity coefficients (alpha Li-Na: 804 and alpha Li-Mg: 387) in a synthetic solution equivalent to the Salar de Atacama brine in Chile. Therefore, this study represents progress towards the industrial application of the lithium recovery process, with potential applications for critical metal recovery in general.

Automated summary

The study introduces a redox-mediated system for selective lithium recovery, which continuously enriches the source water and simultaneously recovers lithium using a selective adsorbent. This system successfully concentrated lithium ions up to 37 mM Li+ with exceptional selectivity, even from extremely dilute lithium-containing solutions. The introduction of lambda-MnO2 as a chemical adsorbent led to high lithium selectivity coefficients in a synthetic solution, showing potential for industrial application of the lithium recovery process.