Performance of manganese oxide sorbents for direct lithium extraction from geothermal brines

Lithium is one of the critical elements for the realization of electric mobility and energy transition. With a contribution to global Li-production and recycling of less than 1% (2017), Europe depends almost entirely on Li-import. To reduce the dependency, new and unconventional Li resources are explored in the EU. One resource are highly saline brines from geothermal reservoirs of the Upper Rhine Graben (URG), characterized by Li concentrations of up to 200 mg/L. Due to space restrictions, conventional production methods are not suitable and technologies for the direct lithium extraction (DLE), such as Li-Mn oxide sorbents, is needed. Lithium-Mn oxide sorbents have a comparably high Li adsorption capacity and due to ion-sieve properties a high selectivity for Li. Batch experiments with synthetic Li+-solutions and natural geothermal brines were conducted to investigate the sorption capacity and kinetics, and the role of competing ions on Li sorption. The batch experiments reveal fast sorption kinetics with an adsorption of >70% of the maximum Li sorption capacity within several minutes. In relation to Li+-solutions, Li sorption decreases for geothermal brines due to sorption of competing ions. While alkaline metals show a relatively little influence, Mn and Ba are the major competing ions. We prove successfully that Li-extraction from geothermal brines in the URG by Li-Mn oxide sorbents is technologically feasible at the laboratory scale. Upscaling into a pilot plant integrated into a power plant is in progress.