Towards near-zero-waste recycling of mine tailings and metallurgical process residues through a novel solvometallurgical process based on deep eutectic solvents

Carboxylic acid-based deep-eutectic solvents (DESs) have been tested for the solubilisation of different metal oxides (TiO2, V2O5, MnO, Fe2O3, Fe3O4, Co3O4, CuO, ZnO, GeO2, In2O3, PbO, Dy2O3, Ga2O3). It has been found that LevA:ChCl(2:1) exhibits the highest solubilities for the studied metal oxides. Moreover, it was also found that for all the studied DESs, the solubility of iron oxide (Fe2O3, Fe3O4) is rather small compared to other metal oxides (ZnO, CuO, MnO). Furthermore, it has been determined that an increase of the water content of the DES drastically increases the solubility of some metal oxides (ZnO, CuO, MnO), while it has a negligible effect in some others (Fe2O3, Fe3O4, Co3O4). Those results suggested that the selective Zn recovery from residues of the Zn smelting process, composed predominantly of Fe- and Zn-, via a solvometallurgical leaching using DESs could be feasible. Experiments on industrial Zn smelting residue using LevA:ChCl(2:1) showed leaching efficiencies of up to 50% for the Zn, while only of 10% for Fe, when DESs with water content ≥ 9 wt% were used. Nonetheless, a higher water content lowered the selectivity against Fe, and resulted in higher Fe impurities in the leachate, compared to a leaching process with lower water content.status: publishe