The flotation behaviour of liberated Platinum Group minerals in Platreef ore under reduced reagent conditions

In spite of numerous studies on PGM behaviour in flotation, there remains much discrepancy regarding PGM speciation and its impact on floatability, as PGMs are routinely considered as an entire group for recovery prediction and trouble-shooting investigations. The understanding of preferential floatability of PGM species under a given flotation regime is important in predicting and addressing mineralogical variability in processing plants, to ensure efficiency in PGM upgrading and recovery. In this contribution, the effect of reduced collector and frother dosages on floatability of individual liberated PGM species was studied in Platreef ore from South Africa, which contains a large variety of different types of PGM species. Reagent tests were performed, with the aim to facilitate a more competitive environment for PGM flotation, by decreasing the collector and frother dosages with respect to a baseline test. Automated mineralogical analysis was performed on the feed, rougher concentrates and tails of the reduced reagent and baseline tests to ascertain how PGM species respond to reducing collector and frother dosages by virtue of the concentrate streams and tails they report to. PtS showed preferential upgrading compared to PdBiTe, PtPdS, PtBiTe, and PtAs, in the reduced reagent test. PdBiTe overall performs better than PtBiTe. PtAs consistently performs the worst in both baseline and reduced reagent tests and is therefore deemed a poorly floatable mineral irrespective of the reagent conditions used. PtPdS, PtAs and PtS floatability seem to be sensitive to grain size with coarse PGM preferentially recovered, over finer grains, in first concentrates. These results can aid in predictive studies for flotation of Platreef ores with variable PGM assemblages, and consequent tailoring of reagent conditions to improve flotation efficiency.