Impact of oxidation on flotation of Ni-Cu sulphide ore with respect to grinding

Impact of oxidation on the flotation of a complex Ni-Cu sulphide has been investigated using two approaches. In the first approach, the samples to be floated were allowed to oxidise before grinding while in the second approach they were allowed to oxidise after grinding. Their flotation characteristics were examined with reference to behaviour of a fresh ore sample. Oxidation before or after grinding has produced an inferior nickel grade-recovery performance. However, the latter case has induced a much greater adverse effect associated with several times more nickel losses and poorer selectivity between pentlandite and pyrrhotite. This was due to over oxidation of part of pentlandite and more importantly enhanced flotation of pyrrhotite which is related to metal ion activation and elemental sulphur formation. Oxidation characteristics of samples in each category are discussed in terms of pH, redox and conductivity behaviour that are utilised for correlations with flotation performance.