Selective Lithium Extraction from Geothermal Brines

The development of future lithium-ion battery technologies will create a demand for cleaner and more versatile lithium sources. Currently, lithium is primarily obtained through ore mining in a limited number of countries, a process that has been associated with significant ecological impacts in the regions where mining occurs. In the United States, there is a growing interest in obtaining lithium domestically from environmentally sustainable sources. One promising option is to extract lithium from geothermal brines found in California's Salton Sea. However, the complex chemical composition of these geothermal brine solutions will require the development of a highly selective separation process to make lithium sourcing from brines an economically viable process.

Researchers have been investigating battery materials as potential ion sieves to selectively capture lithium from geothermal brines. One such material is iron (III) phosphate (FP), which has demonstrated the ability to capture and release lithium through redox cycling mechanisms. When reduced, FP has a strong preference for capturing lithium over other cations found in geothermal brines. Subsequently, a separate oxidation process can be employed to release lithium in a more concentrated and cleaner form suitable for further downstream processes.

The goal of this research is to determine the optimal reaction conditions to maximize the selectivity of lithium capture during the reduction of solid-phase FP. Using these optimized conditions, a laboratory-scale plug flow reactor was used to demonstrate lithium capture and assess its viability for larger-scale production processes. The findings obtained from this study can provide insights for the development of other separation techniques utilizing redox-coupled adsorption processes.