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.