A number of hydrometallurgical treatment methods are being developed to extract copper from chalcopyrite flotation concentrate including microbial leaching and ferric sulfate leaching. However, chalcopyrite is difficult to process efficiently by hydrometallurgical methods as it exhibits slow reaction kinetics. Comparative leaching tests do not always satisfactorily explain or predict observed copper recovery, acid consumption, or differential leaching of minerals. This is especially true when reactive gangue constituents are present._x000D_
The aim of this study was to determine how the leaching regime (microbial versus ferric sulfate) affects both the extraction of copper and residue mineralogy. Chalcopyrite flotation concentrate was leached at 30C and 65C using a pure culture of Acidithiobacillus ferrooxidans and a mixed consortium of thermophiles, respectively. In addition, the concentrate was leached at the same temperatures using 0.1 M ferric sulfate._x000D_
Microbial leaching of chalcopyrite extracted more copper than ferric sulfate oxidation of chalcopyrite at 30C, demonstrating that the microbes promoted the solubilisation of copper at this temperature. This result was confirmed by leach solution analyses and residue analysis using quantitative X-ray diffraction (QXRD). More chalcopyrite was oxidized with ferric sulfate at 65C than at 30C (as expected). QXRD confirmed that pyrite reacted during ferric sulfate leaching at 65C but was relatively unreactive during lower temperature leaching. The high ferric ion concentration in the ferric sulfate leach at 65C led to significant precipitation of jarosite. This phase was only detected in small amounts at 30C in both the microbial and ferric leached residues. Sulfur also precipitated in the ferric leaching at 65C whereas no sulfur was detected in the microbial leached residue. Quartz was a relatively unreactive mineral phase regardless of the leaching medium and temperature. QXRD analysis indicated the residue mineralogy differed with different leaching regime.