CAS-SC: Thermally Switchable Organic Solvents for Targeted Harvesting of Lithium Ions from Alkali Metal Cations Mixtures in Hypersaline Brines

Developing new technologies to extract lithium from unconventional sources more efficiently and sustainably will enable the production and reuse of domestic lithium resources. Lithium can be found in geothermal brines and other unconventional sources such as oil and gas production waste streams. However, the lithium-ion concentration in these brines is much lower than other ions like sodium, potassium, and magnesium. Separating lithium from these brines is challenging because lithium is chemically similar to other alkali metal cations, including sodium and potassium. This project aims to advance a sustainable chemistry-based approach for extracting lithium ions from aqueous brines. The project will have several beneficial outcomes, including developing energy-efficient processes to recover and recycle critical minerals from waste, improving the efficiency of at-scale separation methods, using renewable energy more efficiently to drive separation processes, and finding sustainable alternatives to processes that rely on expensive and toxic chemicals. These advancements in lithium separation will have a transformative effect on energy security by increasing lithium production from conventional sources, unlocking lithium resources from unconventional sources, and making the recycling and reuse of existing lithium more economically viable. Additionally, the project includes educational and research components to train and prepare high school, undergraduate, and graduate students in STEM subjects.This project aims to understand the fundamental governing phenomena in switchable solvent extraction for ion-selective brine mining. The research integrates physical chemistry thermodynamic principles with bulk-phase experimental characterizations to improve selective ion separations. The specific project objectives are to: 1) establish the principal ion properties governing competitive partitioning behavior in biphasic mixtures of switchable solvents and hypersaline brines, 2) determine the intrinsic solvent structure-property relationship and ion-specific selectivity performance, and 3) formulate a thermodynamically-rigorous physical chemistry framework for a priori determination of ion activity coefficients in multicomponent biphasic systems. The research plan will systematically elucidate the underlying mechanisms of preferential ion partitioning in biphasic systems of oleo-solvents and multi-electrolyte aqueous brines. These mechanistic insights will inform future direct lithium extraction technology advancements. The project’s educational activities include (i) developing modules for K–12 education and public outreach, (ii) enhancing undergraduate and graduate courses, (iii) providing undergraduate research opportunities, and (iv) actively recruiting, mentoring, and advocating for underrepresented groups in STEM.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.