Extraction of PGMs from Low-grade Oxide Mineral Deposits

The thesis investigates alternative extraction strategies for platinum group metals (PGMs) from low-grade, high-chromium oxidized ores, which are increasingly important due to the depletion of sulfide PGM deposits and geopolitical constraints on primary producers. Conventional processing routes, based on flotation, smelting, and matte refining, deliver poor recoveries and uneconomic concentrate grades when applied to oxidized PGM mineralization, leading to most such resources being stockpiled or discarded. Building on the limitations of the patented “Panton process,” this research develops and evaluates a novel, non-smelting hybrid pyro–hydrometallurgical flowsheet suitable for a broad range of chromite-rich oxidized and mixed oxide/sulfide ores. Focusing on ores in which platinum occurs predominantly as sperrylite and palladium as antimonides, the study employs sulfation roasting, atmospheric leaching at ambient pressure and in air, and ion-exchange adsorption, with extensive recycling and regeneration of reagents. The work identifies key factors controlling Ni and Cu extractability after sulfation roasting, demonstrates effective single- and two-stage atmospheric leach processes for PGM-bearing oxidized ores, and proposes a conceptual hybrid process that directly produces refinery-ready PGM feed from ore or flotation concentrate. The resulting flowsheet offers improved PGM recoveries, lower effluent generation, and enhanced water and reagent efficiency, thereby providing a technically and economically promising route for unlocking currently untreatable oxidized PGM resources.