Recovery of Pt and Pd from PGM Mine Tailings by Magnetic Separation

Abstract

Application of dry magnetic separation process to recover platinum (Pt) and palladium (Pd) contained in PGM (platinum group metals) flotation tailings (Mixture of Merensky and UG-2 from operations in South Africa was investigated in this work. Ore from UG-2 mainly contains chromite where PGMs are associated with and report to tailings during flotation. Concentrating chromite by magnetic separation can allow possible recovery of the PGMs into chromite product and further recovered by using NiS-FA process. The content of Pt and Pd in the tailings was 0.7 g/t and 0.2 g/t contained in mainly MgSiO₃ and MgCr₂O₄ minerals. A dry coil magnetic separator with its strength varied from 120 to 240 mT was used to separate the tailings into magnetic, middling and non-magnetic fractions in a two-stage operation. Up to around 2 wt% of the tailings was recovered as magnetic fraction in the final stage with Pt and Pd contents exceeding 42 g/t and 13 g/t respectively with total recovery of about 30% and 34%. About 8 wt% of the tailings reported to the middling section giving Pt and Pd contents at 8.3 g/t and 5.33 g/t with a total recovery of 5.9% and 13.2% respectively. XRD studies of the three fractions from magnetic separation show MgCr₂O₄ and MgSiO₃ as main phases in the magnetic and middling fractions indicating that Pt and Pd are contained in MgCr₂O₄. The results indicate that a dry magnetic separation process could be used to concentrate Pt in PGM flotation tailings to over 40 g/t and offer as the additional resource for recovering Pt and Pd.