Characterization of platinum group minerals in the UG-2 chromitite flotation concentrates from the western Bushveld complex, South Africa

Abstract

The Bushveld Igneous Complex (BIC) of South Africa hosts approximately 80 percent of the world economic resources of platinum group elements (PGE). Platinum group elements in the Upper Group 2 (UG-2) chromitite layer of the Bushveld Igneous Complex of South Africa are recovered by the process of comminution and flotation. The recovery of Platinum Group Minerals (PGM) from the UG-2 chromitite is mostly dependent on mode of occurrence, degree of liberation, and grain sizes. PGM in the UG-2 chromitite are recovered by means of flotation. Flotation occurs both in the primary rougher circuit (PRC) and secondary rougher circuit (SRC). In the primary rougher circuit, PRC 1 and PRC 2 are considered as fast floating cells, while PRC 3 to PRC 10, considered as moderate to slow floating cells. The highest recovery of PGM is in PRC 1 and PRC 2. PGM that are recovered in PRC 1 and PRC 2 are mostly coarser, liberated PGM, and PGM associated with coarser liberated Base Metal Sulphides (BMS). PGM recovered from PRC 3 to PRC 10 have smaller grain sizes and are mostly associated with BMS and gangue minerals. In the primary rougher concentrates more than 90 volume percent of PGM recovered are platinum containing sulphides. PGM alloy, PGM containing arsenic, and PGM containing tellurium make up only less than 10 volume percent of recovered PGM in the primary rougher concentrates. The platinum containing sulphides recovered in the primary rougher concentrates in the order of decreasing abundance are braggite (PtPdNiS), cooperite (PtS), malanite (Pt2CuS4), and laurite (RuS2).