SURFACE MODIFICATION OF LITHIUM MANGANESE OXIDE FOR LITHIUM EXTRACTION FROM FILED BRINE

The global demand for lithium has increased due to the recent boom in the electric vehicle industry, and additional resources are necessary to meet the growing demand. The concentration of lithium in brines generated during hydrocarbon recovery processes ranges widely, and while lower than typical salar and hard rock sources, can be a potential alternative source of lithium. Lithium-manganese-oxide (LMO) sorbents, such as Li_1.6Mn_1.6O₄, can selectively separate lithium from saline field brines via an ion exchange process. Organics in the brine can reduce Mn⁴⁺ to Mn³⁺, leading to sorbent loss through the reductive dissolution of manganese. In this study, we used zirconium butoxide to coat Li_1.6Mn_1.6O₄sorbent with ZrO₂ in order to impede manganese reduction and increase sorbent recyclability. Furthermore, we assessed the impacts of sorbent particle size (<75 µm—1000 µm) and ZrO₂ coating thickness (0.2 – 15 µm) on lithium uptake and Mn-loss during the lithium extraction process. To isolate brine-specific effects including organic compounds, extraction experiments were repeated using a synthetic brine which replicates the inorganic chemistry of the field brine. Experimental results indicate that sorbents with smaller particle size have higher lithium uptake. Increasing the coating thickness decreases Mn-loss. The highest Li-uptake (24 mg/g) and lowest Mn-loss (0.5 (w/w)%) were observed for a sorbent with <75 µm particle size and a ZrO₂ coating thickness of 1.1 µm. The relatively high Li-uptake capacity (as compared to the bare sorbent 29 mg/g) after coating could be because the small ionic radius of Li⁺ allows it to permeate the ZrO₂ coating. The sorbent loss during the Li recovery process was similar for both field and synthetic brines, suggesting that organic compounds in the tested brine do not have significant impacts on the Mn-loss. However, the results from this study indicate that the ZrO₂ coating of LMO sorbent can effectively reduce Mn-loss by 50% by physically limiting Mn loss during the delithiation step. Further studies are required to assess the recyclability of Zr-coated LMO sorbents and their potential applications for large-scale lithium extraction from field brines.