The role of the reagent suite in optimising pentlandite recoveries from the Merensky reef

The Platinum group elements (PGEs) in the Merensky Reef in the Bushveld Complex are strongly associated with the sulphide minerals, particularly pentlandite which contains significant amounts of PGEs such as palladium and rhodium in solid solution. The various operations use different reagent combinations in the flotation process to recover PGEs from the Merensky Reef which include primary and secondary collectors, copper sulphate (CuSO4) as an activator and depressants, either carboxymethylcellulose (CMC) or modified guar gum (guar). This study examines the effect on two different ores, A and B, using dibutyl dithiophosphate (DTP) as a secondary collector in combination with sodium isobutyl xanthate (SIBX) as primary collector, the point of collector addition (mill or cell), the use of CuSO4 addition, sequence of CuSO4 addition and the effect of depressant type on the floatability of pentlandite, and shows that pentlandite floatability in contrast to that of chalcopyrite is reduced when reagents were added to the cell rather than the mill together with CMC. This effect was not observed with the use of guar gum as the depressant.