Combined Hydro–Solvo–Bioleaching Approach toward the Valorization of a Sulfidic Copper Mine Tailing

Innovative and sustainable technologies are being developed to meet the demand for critical and economically important metals and to minimize and valorize the increasing quantities of industrial waste streams. This study investigates a valorization route for the recovery of copper from a copper sulfide tailing (0.4 wt % Cu). Microwave-assisted roasting was used to transform the sulfidic fraction into a sulfate fraction, which increased the solubility of copper and other heavy metals during the following leaching steps. The roasted material was leached with an ammonia solution, and the effect on the leaching efficiency of varying the ammonia concentration was investigated. Simultaneous ammoniacal leaching and solvent extraction resulted in a high leaching efficiency of copper (nearly 100%) with a high selectivity against iron (less than 1% leaching efficiency). An indirect bioleaching step with biogenic citric acid, supported by a comparative leaching using purified organic acids, was applied to further decrease the concentration of residual metals (i.e., more than 40% leaching efficiency for Mn, around 20% leaching efficiency for Zn, and 5% leaching efficiency for Cu) and simultaneously neutralizing the pH of the substrate. A standardized environmental leaching test was performed on every leaching residue to evaluate the performance of the process.