Effect of oxidation on the flotation of copper sulphide minerals
The flotation recovery of sulphide minerals generally decreases after oxidation of their surface and therefore a high amount of collector is needed to restore recovery. This is indeed what happened to a copper ore that has been left to oxidise. It was also found that the recovery of the fine copper particles was more affected by oxidation than the coarse particles in the ore.
Time of flight secondary ion mass spectroscopy has shown that the copper sulphide particles in the oxidised ore have more oxide and hydroxide species on their surface than in the non-oxidised ore. Also, less sulphide species are detected on the oxidised ore because there are covered with the oxide and hydroxide surface layer.
X-ray photoelectron, dissolution and zeta potential measurements were used to study the oxidation of each copper sulphide mineral present in the copper ore. It was found that chalcocite is the most reactive of the four copper sulphide minerals, followed by bornite, covellite and chlacopyrite. The oxidation product on the chalcocite and covellite surfaces is copper oxide/hydroxide and mainly iron oxide/hydroxide on the surface of bornite and chalcopyrite. The surface coverage of these oxidation products is relatively thin or patchy as copper sulphide or iron sulphide is also detected.
Copper recovery can be restored with increasing collector concentration.