A review on assessment of ionic liquids in extraction of lithium, nickel, and cobalt vis-à-vis conventional methods

This review discusses the extraction of critical metals (Li, Co, and Ni) using ionic liquids. Here, ionic liquids act as solvents for the separation and extraction of metals. In addition to extraction, they can be used as a lixiviant to leach out metals from spent lithium-ion batteries. Leaching and extraction of metals from the leachate can be performed using a single ionic liquid solvent. Lithium, cobalt, and nickel have been discussed in detail as per their reactivity towards an ionic liquid based on the extraction efficiency and reusability of the ionic liquid. Recycling and reusability of ionic liquids are crucial parameters to be considered while using them as solvents for extracting metals. Moreover, all the other methods such as solvent extraction, ion exchange, ionic liquids, and DES-based separation of metals are compared with respect to their extraction efficiency, cost-effectiveness, and reusability.