Mechanism and process study of lithium extraction by 2-ethylhexyl salicylate extraction system

Abstract

With the increasing demand for lithium resources, recovery of lithium from solution with high Na/Li ratio is an effective way to meet the growing demand. Salicylate extraction system has been found to be an effective system for Li/Na separation. In this work, the studies of equilibrium, process and mechanism were carried out for the 2-ethylhexyl salicylate (ES) and trialkyl phosphine oxide (TRPO) co-extraction system. The factors affecting lithium extraction such as composition of the organic phase, the conditions of aqueous phase, extraction time and acid-alkali tolerance of the ES extraction system were systematically investigated; According to the equilibrium study, a series of process studies were carried out for lithium recovery from mother solution of lithium carbonate, and the whole process including extraction, elution, stripping and regeneration was designed, and through the process, 99% of lithium was recovered and lithium-rich solution containing 25.85 g/L Li and 0.08 g/L Na was obtained. In the mechanism study, the extraction process was proved as a thermodynamic spontaneous entropy increase process; At the molecular level, the coordination mechanism was first expounded by ultraviolet–visible (UV–Vis) and fluorescence spectrum (Fl), which was further confirmed by 1H NMR and Fourier transform infrared (FT-IR). The current study points a way to separation of lithium from alkaline solutions, which will support the future supply of lithium in a more economical and sustainable manner.