Selective lithium extraction from geothermal brines by sorption

Lithium is an important compound in several industrial applications and is mostly found in lithium ion batteries (LIBs), ceramics and glass. Lithium deposits are hosted in pegmatites, sedimentary rocks and brines (i.e., salt lakes, salars, oilfield brines, and geothermal brines) comprising 25 - 26 %, 8 % and 59 - 66% of the world’s Li resources, respectively. Geothermal brines in the Upper Rhine Graben, Germany, with Li concentrations of up to 200 mg/L and resources of 2.7 Mt Li2CO3 represent potentially economically mineable Li deposits. The scope of our project is to extract Li from these high saline (i.e., TDS ~100 - 200 g/L) geothermal brines by sorption using natural and synthetic zeolite and clay minerals. These high saline brines are slightly acidic in pH and characterized by high concentrations of major cations (e.g., Na+ up to 60 g/L, K+ up to 4 g/L, Ca2+ up to 11 g/L and Mg2+ up to 1.9 g/L) and anions (e.g., Cl- up to 120 g/L and SO42- up to 1.5 g/L). Synthetic zeolite 13X and natural clinoptilolite-mordenite-montmorillonite mixtures have been used for preliminary sorption experiments. We performed batch sorption experiments with synthetic Li-solutions and variable concentrations and temperatures between 25 – 60 °C. Furthermore, we studied the effect of competing ions (e.g., Na+) on Li-sorption. Thereby, we investigate the different materials for sorption capacity and kinetics, chemical stability, structural effects of Li incorporation and their applicability to geothermal brines.