Lithium extraction from a multicomponent mixture using supported liquid membranes

Increasing demand for lithium metal is expected to rise above the current production levels. Most lithium production is currently from mining and recovery of pegmalite ores. Recent research has emphasized recovery from brine sources such as geothermal water and seawater. A novel liquid-membrane-extraction process is investigated here for the recovery of lithium metal from these natural resources. Different carriers and combinations of carriers were tried for lithium selectivity. A carrier combination of LIX54 (main component is a-acetyl-m-dodecylacetophenone) and TOPO (tri-octyl phosphine oxide) had a synergistic effect for lithium extraction and was found to be most effective. This combination was used to extract lithium in a supported liquid membrane (SLM) process. Variables considered were pH, carrier concentrations, initial lithium concentration, type of organic solvent and stripping phase and presence of sodium and potassium ions in the feed and flow rates of both aqueous phases. The optimal extraction efficiency of the system was higher than 95% for a model feed solution containing Na⁺, K⁺, and Li⁺ at pH greater than 12.5. The permeability of the system was maintained at a constant value for a maximum period of 2 days and dropped below 50% after 4 days. Empirical mathematical models for lithium extraction were derived from the results of SLM experiments.