Liquid membranes for the selective extraction of lithium ions from brine: A review

The surging global demand for lithium, driven by its essential role in batteries for electric vehicles, portable electronics, and energy storage systems, underscores the need for efficient and sustainable extraction technologies. This review provides a comprehensive analysis of liquid-based membrane technologies (bulk liquid membranes (BLMs), supported liquid membranes (SLMs), and polymer inclusion membranes (PIMs)) for selective lithium extraction from brine sources. These membranes employ carrier molecules such as crown ethers, organophosphorus compounds, and ionic liquids to achieve high selectivity over competing ions through facilitated transport mechanisms. BLMs, primarily used in laboratory settings, utilize various configurations enabling selective complexation and diffusion driven by chemical gradients. SLMs enhance practical applicability through porous polymeric supports impregnated with organic phases, improving stability and performance. PIMs integrate base polymers with extractants and plasticizers, offering enhanced durability and environmental advantages by minimizing solvent use. This review addresses critical factors affecting performance, including carrier selection, aqueous phase composition, and membrane stability, while highlighting challenges such as fouling, carrier loss, and energy demands in electrically driven systems. Future research directions include developing bio-based carriers, optimizing membrane designs for industrial scalability, and exploring unconventional lithium sources to meet growing market demands while reducing environmental impact.