The processing of ore by hydrometallurgy or pyrometallurgy typically has a high energy demand, and associated release of carbon dioxide. Thus there is a need to develop more energy-efficient and environmentally-compatible methods. Here, we show that ionic liquids are one such method, and that they can be used to selectively dissolve and recover native gold and tellurium, sulphides and tellurides. Ionic liquids are anhydrous salts that are liquid at low temperature. They are powerful solvents and electrolytes with potential for high selectivity in both dissolution and recovery. Deep eutectic solvents (DES) are a form of ionic liquid that are mixtures of salts such as choline chloride with hydrogen-bond donors such as urea. DESs are environmentally benign, yet chemically stable and, furthermore, the components are already produced in large quantities at low cost.Gold, galena and chalcopyrite, as well as tellurobismuthite (Bi_2Te_3), are soluble in DES by oxidation at 45-50°C at rates that are very favourable in comparison to cyanidation, bio-oxidation or high-T hydrometallurgy. Pyrite is notably insoluble under the same conditions. In contrast, pyrite, arsenopyrite, and indeed any sulphide, can be selectively dissolved by electrolytic reduction in a DES, thus suggesting a protocol whereby target inclusions can be liberated by reduction and then dissolved by subsequent oxidation. Ionometallurgy could offer a new set of environmentally-benign tools for metallurgists.
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