Processing partially oxidized sulphide ores poses unique metallurgical challenges due to surface oxidation layers that impair mineral recovery. Key implications include reduced flotation efficiency from hydrophilic iron hydroxides and potential pyrite activation via copper dissolution(Tayebi-Khorami et al., 2018).
Surface oxidation plays a crucial role in flotation behavior, initially forming metal-deficient, sulphur-rich layers that can enhance collectorless flotation; however, with continued oxidation, hydrophilic species such as iron hydroxides develop on the mineral surface, hindering collector adsorption and reducing both efficiency and selectivity. Studies on copper sulphides illustrate this progression, showing that early oxidation can activate pyrite due to copper ions leached from the surface, temporarily improving flotation performance, but prolonged exposure ultimately leads to a significant drop in recovery, decreasing from about 90% to around 65% as surface conditions become less favorable for flotation(Jacques, n.d.).
Effective processing strategies focus on controlling grinding chemistry to limit the negative effects of oxidation. For example, using high-chrome grinding media helps maintain more oxidative pulp conditions, reflected in higher redox potential (Eh) and dissolved oxygen (DO), which enhances copper recovery and improves selectivity between chalcopyrite and pyrite compared to forged steel media. In addition, alternative approaches such as sulfidization can be applied to treat mixed ores, while hydrometallurgical leaching offers a way to bypass flotation challenges altogether(Treatment of Mixed Sulfide Oxide Ores of Copper – 911Metallurgist, 2016).
Reference:
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Jacques, S. (n.d.). Oxidative weathering of a copper sulphide ore and its influence on pulp chemistry and flotation.
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Tayebi-Khorami, M., Manlapig, E., Forbes, E., Edraki, M., & Bradshaw, D. (2018). Effect of surface oxidation on the flotation response of enargite in a complex ore system. Minerals Engineering, 119, 149–155. https://doi.org/10.1016/j.mineng.2018.01.024
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Treatment of Mixed Sulfide Oxide Ores of Copper—911Metallurgist. (2016, September 26). https://www.911metallurgist.com/blog/treatment-mixed-sulfide-oxide-ores-copper/
