The effect of grinding conditions on the flotation of a sulphide copper ore

The challenge of process development for the beneficiation of Salobo’s copper ore started in 1978 and the studies still go on. Copper is predominantly present as secondary minerals, such as chalcocite, bornite, and digenite, and liberation requires very fine grinding. These minerals may undergo rapid oxidation at the alkaline pH range and under mildly oxidising conditions. The oxidation products may adsorb onto the minerals altering their surface characteristics, flotation behaviour, and may also significantly modify the mechanisms of interaction between the minerals and the collector. These facts impair the flotation process performance and increase the reagents consumption, the required flotation cells volume, and the overall processing costs. This paper describes the effect of grinding conditions on the flotation performance. Different media and mill construction materials were tested at bench scale aiming at evaluating the effects of the pulp electrochemical potential and the availability of iron oxide and hydroxide compounds on the flotation response. The results indicated that the grinding process affects significantly the flotation metallurgical performance of Salobo’s ore. The conditions that yielded the highest levels of copper recovery and the fastest flotation kinetics were rubber lined steel mill and stainless steel media.