Dr. Cabezas-Cornejo, René

Cobalt (Co) stands out as one of the most critical metals in contemporary use, particularly due to its increasing demand in technological products and especially in electromobility. Over the years, ionic liquids (ILs) have provided a green alternative to volatile organic solvents in hydrometallurgy due to their outstanding properties, such as the negligible vapor pressure and their increased selectivity provided in separation processes, which opens the possibility to ramp up the Co-production while maintaining sustainable mining processes. Thus, this review offers a complete comprehensive and critical summary of published works on the use of ILs in the hydrometallurgy of Co, starting from the leaching from a primary source by conventional methods and then, from the pregnant leach solution (PLS) focuses on the advantages and disadvantages of solvent extraction (SX) in different aqueous media (chlorinated, nitrated, and sulfated) in which ILs are used to separate selectively Co from a multi-metal mixture. In the following section, its recovery from the loaded organic phase by acid stripping is discussed. Finally, this review provides the challenges that ILs should overcome to be viable for large-scale industrial applications and the opportunities that exhibit for selective recovery of Co from PLS capitalizing.

Background: Rhenium(Re) is a highly valuable metal recovered from molybdenite leach liquors by solvent extraction (SX) using toxic organic solvents. This work proposes an extracting phase free of volatile organics composed by the ionic liquid (IL) trioctylmethylammonium benzoate [TOMA][BA] as the extractant, due to its ability to extract Re(VII), and the IL 1‐octyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide [omim][Tf2N] as the diluent, due to its high hydrophobicity where the extraction stoichiometry and process parameters such as the initial pH, the extractant concentration in the diluent and stripping using ammonium hydroxide () and sodium hydroxide () were assessed. Results: This extracting phase yielded high extraction percentages: 95% with only 3% (v/v) of [TOMA][BA] in [omim][Tf2N]. A detailed study of the SX stoichiometry was carried out through slope analysis, showing that the SX occurs in two steps: first, the extraction of acid; then, the extraction of the metal ion via anion exchange with the transfer of IL‐diluent anion to the aqueous phase. Additionally, the extracting phase was tested in a synthetic molybdenite leached pregnant leach solution, showing selectivity towards Re(VII) over Cu(II) and Fe(III) at very low extractant concentration. The stripping of Re(VII) from the loaded phase was also studied achieving 60% stripping in only one equilibrium step when using . Conclusion: This novel extracting phase, free of volatile organic, shows promising Re(VII) extraction for future industrial applications.