Sustainable copper extraction from mixed chalcopyrite–chalcocite using biomass
(1. Mineral Processing and Technology Research Centre, Department of Metallurgy, School of Mining, Metallurgy and Chemical Engineering, Faculty of Engineering and the Built Environment, University of Johannesburg, Doornfontein Campus, P. O. Box 17911, South Africa;
2. Materials & Process Engineering (iMMC-IMAP), UC Louvain, Place Sainte Barbe 2, 1348 Louvain-la-Neuve, Belgium;
3. Department of Industrial Chemistry, Faculty of Polytechnique, University of Likasi, 177, Shituru Campus, P. O. Box 1946, Likasi, Democratic Republic of the Congo)
2. Materials & Process Engineering (iMMC-IMAP), UC Louvain, Place Sainte Barbe 2, 1348 Louvain-la-Neuve, Belgium;
3. Department of Industrial Chemistry, Faculty of Polytechnique, University of Likasi, 177, Shituru Campus, P. O. Box 1946, Likasi, Democratic Republic of the Congo)
Abstract: This paper elaborated on the sustainability of the copper extraction process. In fact, an alternative copper extraction route from mixed sulphide ores, chalcopyrite and chalcocite using mesophilic biomass consortium at 33.3 °C and ferric leaching process were attempted. Bioleaching experiments were settled with a fraction size of -75+53 μm. Bacteria were used as the catalyst. A copper yield of 65.50% was obtained. On the other hand, in ferric leaching process, with a fraction size of -53+38 μm, when the temperature was increased to 70 °C, the copper leaching rate increased to 78.52%. Thus, comparatively, the mesophilic bioleaching process showed a more obvious advantage in copper extraction than leaching process with a high temperature. However, it has been resolved from the characterization performed using SEM-EDS, FTIR and XRD observations coupled with different thermodynamic approaches that, the indirect mechanism is the main leaching mechanism, with three transitory mechanisms (polysulphide, thiosulphate and elemental sulphur mechanisms) for the mixed chalcopyrite-chalcocite ore. Meanwhile, the speciation turns into Cu2S-CuS-Cu5FeS4-Cu2S before turning into CuSO4. While ferrous oxidation and the formation of ferric sulphate occur, and there is a formation of strong acid as bacteria digest sulphide minerals into copper sulphate at low temperature, which is why this copper production scenario requires a redox potential more than 550 mV at room temperature for high copper leaching rate.
Key words: sustainable copper extraction; mixed chalcopyrite-chalcocite; copper speciation; ferric leaching; mesophilic bioleaching mechanism; redox potential