The Role of Oxidants in Metal Extraction from Sulfide Minerals in a Deep Eutectic Solvent

The advantages of using deep eutectic solvents (DES) as a promising leaching media have been highlighted in research publications, however, a clear understanding of the leaching efficiency of valuable minerals and metals in such media is not available yet. In this study, we conducted leaching experiments on a a sulphide flotation concentrate in Ethaline, a very well-known DES, in the presence of common oxidants. The results were compared to those of aqueous solutions of similar chloride concentration to address solely the effect of leaching media on leaching behaviors. Thermodynamic modeling was also conducted in this regard. Leaching experiments were performed on the concentrate containing a combination of sulfide minerals as well as significant concentrations of minerals carrying Au, Ag, and Te. The results enabled us to acquire a preliminary view of the leaching behavior of such minerals and metals in Ethaline. To achieve this goal, a mineral-based interpretation of results was followed. Results revealed a similar leaching behavior among Ethaline and chloride aqueous solution in non-oxidative leaching. Higher leaching efficiencies were observed in Ethaline in the presence of oxidizing agents. Galena dissolution occurred through both non-oxidative and oxidative routes where the leaching rate is faster in the aqueous solution. Other sulfide minerals undergo mainly oxidative dissolution. While the oxidation rate of pyrite in Ethaline is very low, higher oxidation rates were observed for chalcopyrite. The results also show that the rate of chalcopyrite leaching varies significantly depending on the oxidants type. The highest recovery was observed in the case of CuCl2 followed by I2 and FeCl3. H2O2 and O2 were found to be less effective. The results also showed a significant improvement in conversions of precious metals in Ethaline compared to the aqueous solution, though a complete conversion was not achieved.