2026 Articles

A novel approach for direct lithium extraction from alkali metal cations in brine mixtures using thermally switchable solvents

Dach, Elizabeth May; Marston, Juliana M.; Abu-Obaid, Sara; Peng, Allison; Yip, Ngai Yin

This study presents a proof-of-concept for switchable solvent selective extraction (S3E) for direct lithium extraction from brines. S3E utilizes an amine solvent with thermally switchable hydrophilicity to extract Li+ and water from the brine, and a modest temperature swing toggles the solvent to its hydrophobic state, releasing a purified lithium product stream and regenerating the solvent. S3E demonstrated a consistent preference for lithium across amines with different chemical structures, achieving Li+/Na+ selectivities as high as ≈10. The selectivity for lithium was maintained even when challenged with Li+ concentrations 1,000× lower than Na+ or K+, whereas Li+/Na+ and Li+/K+ selectivities for a simulated Salton Sea geothermal brine are ≈13 and ≈24, respectively, with magnesium completely removed as Mg(OH)2 precipitates due to the basicity of the amine solvent. Furthermore, repeated semibatch extraction cycles reusing the solvent demonstrated practical Li+ recovery yields (40% after four cycles) and solvent regenerability while preserving selectivity.

Keywords: direct lithium extraction, DLE, switchable solvents, alkali metal cation selectivity, critical materials, ion selective separation, geothermal brines, liquid-liquid extraction, solvent extraction