Novel Application of Thermal Swing Salting-out (TSSO) Process for Lithium Extraction from Hypersaline and Unconventional Brines

Abstract

The global transition to a low-carbon energy future has substantially increased the demand for lithium, a key element in lithium-ion batteries (LIBs) essential for electric vehicles (EVs) and renewable energy storage systems (ESS). Current commercial lithium production primarily relies on hard-rock ores and continental brines; however, conventional solar evaporation processes are limited by extended processing times (12–24 months), low recovery rates (20–50%), and excessive water consumption, particularly in arid regions. To address these challenges, this study proposes a novel Thermal Swing Salting-Out (TSSO) process to enhance lithium recovery from hypersaline and unconventional brines, including geothermal brines. The TSSO process builds on the principles of temperature-swing solvent extraction (TSSE) by utilizing the temperature-responsive phase behavior of diisopropylamine (DIPA) to induce selective salting- out of impurity salts while concentrating lithium in the aqueous phase. Experimental results with synthetic ternary and quaternary brines demonstrated that the TSSO process effectively reduced NaCl and KCl concentrations and achieved more than two-fold lithium enrichment under optimized conditions. In addition, the process facilitated calcium removal through alkaline precipitation, improving selectivity in complex brine systems. Validation using a simulated geothermal brine representative of the Salton Sea confirmed the process's feasibility, achieving approximately 60% lithium recovery. Overall, this study demonstrates that the TSSO process offers a promising alternative to conventional evaporation-based lithium extraction, offering significantly reduced processing time (~4 hours), enhanced selectivity for lithium over impurities, and efficient utilization of low-grade thermal energy. These attributes position TSSO as a viable and sustainable technology for lithium production, particularly suitable for deployment in remote and resource-constrained environments.