A XANES and XRD study of chalcopyrite bioleaching with pyrite

•Microbes negatively impacted chalcopyrite galvanic leaching at 30 °C.•Chalcopyrite was preferentially leached at lower Eh in chemical leaching.•Pyrite was preferentially leached at higher Eh in bioleaching.•The presence of microbes decreased the chalcopyrite leaching selectivity.

The galvanic effect between chalcopyrite and pyrite was investigated by solution studies, X-ray Diffraction (XRD), and synchrotron X-ray Absorption Near Edge Structure (XANES). The solution studies indicate chalcopyrite leaching efficiency was significant improved in galvanic assisted leaching with more than 90% of copper being dissolved in 31 days in leaching at both 48 °C and 30 °C. In contrast, the addition of microorganism negatively affected the leaching efficiency at 30 °C. XRD and iron K-edge XANES analysis indicate the presence of microorganisms decreased the chalcopyrite leaching selectivity, likely linked to the increased solution potential. Chalcopyrite was selectively leached in chemical leaching as a result of galvanic effect. On the other hand, dissolution rate of pyrite was fast in the case of bioleaching where the Eh was high.