Lithium (Li) is a highly reactive alkali metal with excellent heat and electrical conductivity properties, making it useful for a variety of industrial applications. Because of Li’s high reactivity, pure elemental Li is not found in nature but is present as a constituent of salts or other compounds found in brines, mineral ores, clays, and seawater. Brines/seawater contain a variety of dissolved minerals, primarily sodium (Na), present in greater quantities than Li, making the selective capture of Li over other dissolved minerals challenging. Numerous techniques (e.g., membrane filtration, ion exchange, RO) have been evaluated for selective extraction of Li from brines/seawater, but these technologies are energy-intensive, can result in fouling of filtration media, and/or use toxic reagents, while use of brine evaporative techniques to selectively extract Li from brines/seawater require extensive land use/time. In addition, Li extraction from brines can have a significant environmental impact, including water pollution/depletion.
Researchers at UT Austin have developed a treatment technique using two novel crown ether strapped calix pyrroles to prepare gels for use in Li separation. Laboratory testing indicated elevated gel selectivity towards LiCl over other competing salts (e.g., NaCl, KCl, MgCl2, CaCl2) in acetonitrile. The captured LiCl can be removed by treating the gels with methanol, and the gels can be recycled for repeated use/adsorption of LiCl. The entire LiCl capture/release process is performed with organic solvents, eliminating issues with water usage and pollution associated with current Li processing techniques. The primary use case for this technology would be application in Li brine processing, with potential additional applications in Li extraction from mine tailings, clays, and spent Li batteries.