Coarse particle flotation (CPF) is one of the strategies employed to reduce energy consumption in mineral-processing circuits. Hydrofloat^TM (HF) technology has been successfully applied in the coarse flotation of industrial minerals and sulphide middlings. However, this technology has not yet been applied in platinum group minerals (PGMs)’ flotation. In this paper, the amenability of platinum group minerals to CPF was investigated. Extensive flotation testwork was conducted to optimise the hydrodynamic parameters, i.e., bed level, air and water flow rates, in the flotation of coarse PGM feed using Hydrofloat. Mineralogical analysis of the feed and selected flotation products was conducted to understand the reasons for the recovery and loss of the valuable minerals. The results showed that the HF separator could upgrade the PGM ore with particles as coarse as +106 − 300 µm. For the optimised test, a reasonable Pt, Pd and Au recovery of 84% was achieved at a grade of 10 g/t and 16.5% mass pull, despite the platinum group minerals being poorly liberated (4.5 vol% fully liberated). The results demonstrated that HF achieved high recovery efficiencies across the 150–300 microns size fraction. The HF was therefore able to substantially increase the upper particle size that can be successfully treated by flotation in PGM operations. It was found that an increase in bed height, water rate and air flow rate resulted in an increase in recovery to a maximum. A further increase in the hydrodynamic parameters resulted in a decline in recovery. Hydrofloat outperformed the conventional Denver flotation machine across the following size fractions: +106 − 150 µm, +150 − 212 µm, +212 − 250 µm and +250 − 300 µm. The practical implications of the findings on the modification of existing circuits and the design of novel flowsheets for the processing of PGM ores with less water and energy consumption are discussed.

Fluorite, CaF₂, is considered a strategically important mineral as it is a raw material for many strategic industries. Froth flotation is reported to be the most efficient and economically viable process for the production of an acid-grade product with a CaF₂ content of at least 97%. Selective flotation of fluorite from gangue minerals, e.g., calcite and barite, is challenging because these minerals have similar physicochemical properties. This study employed batch flotation tests coupled with mineralogical analysis to design suitable customised flowsheets and efficiently optimised reagent regimes for optimum production of acid-grade fluorite concentrate from two different fluorite ores by the froth flotation process. The effect of pulp temperature on fluorite flotation was investigated in this study with the objective of lowering pulp temperatures in fluorite flotation. The results showed that an acid-grade CaF₂ concentrate could be obtained from the flotation of both ores at ambient pulp temperatures. This eliminates the requirement for high-temperature pulp treatment, which would result in a significant reduction in thermal energy costs. This study showed that an understanding of gangue mineralogy is key to process optimisation for acid-grade CaF₂ production. Although an acid-grade CaF₂ concentrate could be produced from both ores, the flowsheets and reagent regimes were markedly different. For instance, the production of an acid-grade CaF₂ product from a high quartz and calcite ore was achieved by employing a simple rougher–multiple cleaner flotation circuit using tannin and sodium silicate as calcite and quartz depressants, respectively. On the other hand, the production of an acid-grade CaF₂ product from the flotation of the pyritic ore required a pre-sulphide flotation stage for upfront sulphur removal and the use of a sulphide depressant. Multiple stages of cleaning were required for improved selectivity in the flotation of both ores.

Declining ore grades, coupled with the increasing mineralogical complexity of ores, have forced the platinum group mineral (PGM) industry to search for collectors that outperform the conventional options. One such potential alternative is Nouryon’s Tecflote™ family of nitrile-based collectors for sulfide flotation; whilst notable success has been reported in the copper industry, the potential value of these in the PGM industry has not yet been evaluated. This study employed batch rougher flotation tests coupled with mineralogical analysis of tailings samples to investigate the application of Tecflote S11 as a partial or complete replacement of thiol collectors in the flotation of a PGM bearing Platreef ore. Tecflote S11 as sole collector and in combination with different thiol collectors were investigated. At low dosages of 80 g/t, the Tecflote and PAX as single collectors achieved similar 3E (Pt, Pd and Au), Ni, and Fe recoveries, with Tecflote proving to be the more powerful Cu collector. At higher dosages of 160 g/t, PAX outperformed Tecflote in terms of 3E, Cu, Ni and Fe recoveries. A 50:50 mass% combination of the Tecflote with either DTP, DTC or PAX showed improved recoveries without a loss in 3E grade. The Tecflote-PAX combination achieved the highest 3E, Cu and Ni recoveries. Under these conditions, fully liberated PGMs and those associated with liberated base metal sulfides (BMS) were recovered. Overall, the study demonstrated that the Tecflote requires the backing of a strong thiol-based collector to achieve an improved flotation response for the Platreef ore.