A thiosystem approach for leaching of platinum group metals from oxidised Great Dyke flotation concentrate

The depletion of high-grade sulphide platinum group metal (PGM) ores has intensified interest in oxidised resources, particularly within the Great Dyke, Zimbabwe. However, these ores pose significant metallurgical challenges due to limited amenability to conventional hydrometallurgical processing. This study investigates a novel, thiosystem leaching route for the recovery of PGMs from an oxidised Great Dyke flotation concentrate. The proposed lixiviant system comprises thiosulphate, thiourea and thiocyanate. Evaluation of reagent combinations identified a lixiviant achieving 41.3% PGMs dissolution. Response surface methodology was applied to optimise reagent concentrations and operating parameters, yielding predicted recoveries exceeding 90%. Mineralogical analyses revealed that enhanced dissolution arises from synergistic oxidation and ligand complexation. A Monte Carlo-based cost–benefit analysis demonstrated the economic advantage of the thiosystem relative to conventional cyanide systems. The results confirm that thiosystem leaching offers a technically viable, economically competitive and environmentally sustainable approach for processing oxidised PGMs ores.