Impacts of grinding media alloys composition on the flotation of mixed oxides-sulphides copper ores.

While the influence of the grinding media alloy composition on the flotation performances of sulphide ores has been widely studied, its role in the flotation of mixed (oxide and sulphide) ores is poorly documented. For some deposits, the mixed ores zone is well developed and can be of great importance for the economics of a mining project. These ore types often present technical challenges for their beneficiation such as sulphides tarnishment, slimes generation, presence of hydrophobic gangue or presence of acid consuming gangue. This study highlights the importance of matching the right grinding media alloy to the mineralogy of the ore, particularly its degree of weathering and to the subsequent flotation scheme. Shifting the grinding media towards less electrochemically active alloys significantly enhanced the grade-recovery curves and the flotation kinetics of the sulphides fraction, particularly when high degrees of sulphides oxidation were induced within the orebody or during stockpiling. For ores with high acid consuming gangue and medium acid soluble copper content that require a preconcentration of the oxide fraction by flotation through activation by sulphidisation, the higher sulphides flotation rates achieved with the use of high chromium alloys limited the amount of sulphides entering the sulphidisation stages and led to a better selectivity between acid insoluble and acid soluble copper allowing better downstream extractive metallurgy performances