The critical degree of mineral surface oxidation in copper sulphide flotation

It is well documented that surface oxidation of copper sulphide minerals has some detrimental effects on their flotation performance. However, little work has been done to quantitatively relate surface oxidation to flotation performance, which makes it inherently difficult for processing plants to optimise flotation conditions for oxidised ores. In this study, an array of oxidised chalcopyrite and chalcocite samples was prepared and characterisation of the surface oxidation species was carried out by X-ray Photoelectron Spectroscopy (XPS). The degree of surface oxidation was quantified as the ratio of hydrophilic species to hydrophobic species and correlated with copper sulphide flotation recovery. A quantitative relationship between them was established and a critical degree of oxidation, beyond which flotation becomes impossible, was identified to be 11.7 for chalcopyrite and estimated to be in the range of 1.74-4.85 for chalcocite, indicating that chalcocite flotation is much more sensitive to surface oxidation. This study will enable provision of guidelines to better manage oxidised copper ores to circumvent the loss of recovery and will also help in developing potential solutions that could be applied to flotation of minerals with different degrees of oxidation.