Deep eutectic solvents (DESs) appeared recently as a new class of green designer solvents. The recovery of metals using hydrometallurgy is of major importance with the growth in metal demand. Several authors used these solvents for the hydrometallurgical recovery of metals from primary and secondary resources, and these studies are reviewed in the present work. Hydrophilic DESs can be used for the leaching of metals and have great potential to replace mineral acids, and even to reduce water consumption. Efficient and selective leaching of metals from minerals or wastes is feasible by using DESs. However, the kinetics of leaching as well as the physicochemical properties of DESs are still limiting their large-scale application. Electrochemical recovery from DES is also possible but deserves further investigation. Finally, the recovery of metals from aqueous solutions using hydrophobic DESs was studied in several works. For the solvent extraction of metals, hydrophobic DESs constitute credible alternative ionic liquids.

Background: Supported liquid membranes (SLMs) and polymer inclusion membranes (PIMs) are an interesting technology for the recovery and separation of metal ions. This kind of membranes could provide the advantages of hydrometallurgy (i.e. high selectivity, possibility to treat low concentration of metals …) without needing a large organic solvent inventory. Problem: However, the large-scale application of SLMs is limited because of the short lifetime of the process. Several authors claimed a longer lifetime when molecular diluents were replaced by ionic liquids (ILs). Possible solutions: In this review, recent advances on the extraction of metals from aqueous solutions using SLMs and PIMs based on ILs are summarized and discussed. The mechanisms of degradation are reported and the improvements as well as limitations outlined. In SLMs, ILs were shown to improve membrane stability. However, stability is improved with viscous ILs having low solubility in water. ILs were used in PIMs as plasticizers and/or carriers and have shown their potential. However, the effect of ILs on PIM structure is not fully understood. To date, extraction of anionic metallic species is the most relevant field of study for SLMs and PIMs. A larger variety of ILs could be studied to apply this technique for a broader range of metals.