The recovery and separation of lithium by using solvent extraction methods

Lithium, the lightest alkali metal, has been called the "new white gold" because of its limited availability and critical importance in arising applications in clean energy, like hybrid and electric vehicles. However, the rapidly growing demand for lithium, combined with its low global production rates, has led to concerns regarding the development of new technologies that require this critical mineral. For this reason, there is a need for cost-effective, energy-efficient, and environmentally friendly approaches to isolate lithium from sustainable resources like brine, ores, and seawater. In this context, solvent extraction is a promising technique for lithium recovery from these sources that has advantages over other approaches like precipitation, solid-state adsorption, and membranes. However, there are few processes in industry that use solvent extraction for lithium extraction and purification. The scarce use of this method industrially is possibly a consequence of critical knowledge gaps that need to be addressed prior to the optimization of processes with suitably high lithium selectivity and extraction efficiency. This review bridges these gaps by highlighting the coordination chemistry of lithium and discussing the requirements for developing highly selective lithium chelators for solvent extraction. Additionally, the lithium coordination properties and solvent extraction performance of macrocyclic and acyclic chelator classes, as well as ionic liquid extraction systems, used to extract lithium from artificial solutions, brines, and seawater are reviewed.