Highly selective lithium extraction by forming ion pairs using 2,9-Dialkyl-1,10-Phenanthrolines and a hydrophobic anion

Abstract

Lithium is becoming increasingly important due to its indispensable role in lithium-ion batteries. The direct extraction of lithium from salt lakes, which are a main source of lithium, is challenging due to the coexistence of many interfering alkali and alkaline earth metals. In this work, we report that a synergistic solvent extraction (SSX) system containing 2,9-dialkyl-1,10-phenanthroline and a hydrophobic anion ([NTf₂]⁻) could extract lithium selectively with a high lithium loading capacity from solutions containing both alkali (sodium, potassium) and alkaline earth metals (magnesium, calcium), enabling the direct recovery of lithium from complex salt lakes. The outstanding lithium extraction performance of the SSX system is unprecedented, to the best knowledge of the authors. Through various characterizations and X-ray diffraction of the complex crystals, the extraction mechanism has been revealed. This SSX system will potentially promote more efficient recovery of lithium from salt lakes.