A review of the recovery of precious metals using ionic liquid extractants in hydrometallurgical processes

A large amount of industrial waste containing precious metals (PMs) has become a significant issue for the recovery of PMs. The success of PM extractions via hydrometallurgical processes using various types of ionic liquid (IL) extractants has been widely reported. An understanding of their extraction mechanisms and influencing factors is advantageous for further development and design, especially future utilization in industries. This review focuses on the extraction mechanisms of PMs using ILs as extractants in the liquid-liquid extraction or solvent extraction process. Factors influencing their extraction mechanisms and efficiency are described. Different types of ILs used in the extractions of gold (Au(III)), silver (Ag(I)), palladium (Pd(II)) and platinum (Pt (IV)) have been promoted. Moreover, the correlation of calculating parameters with the PM extractions is presented. Finally, their future aspects are recommended.