(348c) Design of Deep Eutectic Solvents for Lithium Recovery from a Brine Solution

Lithium (Li) is used in various applications, such as lithium-ion batteries, and lubricating greases. Because of the widespread use of lithium-ion batteries, the consumption of Li resources is expected to reach more than 90 000 tons in 2025. The amount of Li in brine is nearly twice that in ore, which means that effective utilization of brine is a more sustainable way to produce Li than from ore. However, brine contains various other elements, which makes the separation of Li more difficult.

We proposed a novel synergistic DES concept for improving the performance of environmentally benign liquid–liquid extraction of lithium (Li). Two different conventional extractants, a beta-diketone and a neutral extractant, were effective for creating the synergistic DESs. When the two extractants were mixed, they formed a liquid DES. DESs have much lower viscosity than conventional hydrophobic ionic liquids. In this study, mixtures of Thenoyltrifluoroacetone (HTTA)/ trioctylphosphine oxide (TOPO) was studied as a new family of DESs. The reusability of HTTA/TOPO-DES demonstrated high stability and could be used for long-term operations. The extraction performance of Li was greatly enhanced with the synergistic DESs. In the liquid-liquid extraction study, synergistic effects have occurred in the Li extraction with the DESs, even though they were solvent-free environments. Using the optimum DES, highly selective recovery of Li over Na and K was demonstrated with a model brine solution.