A conceptual flowsheet for heap leaching of platinum group metals (PGMs) from a low-grade ore concentrate

This research proposes a new conceptual process to economically extract platinum group metals (PGMs), and as a secondary aim, base metals (BMs) from a low-grade concentrate originating from typical PGM concentrator plants. Slurry made from the concentrate was coated onto granite pebbles and packed into a column, in which it was bioleached with a mixed culture of thermophiles and mesophiles at 65 °C. After 30 days the extractions achieved were 52% copper, 95% nickel and 85% cobalt. The residual concentrate material was subsequently subjected to a cyanide leach also in a packed column operating at a room temperature of 23 °C. After 21 days 20.3% Pt, 87% Pd and 46% Rh were extracted. Using these results and projected extractions over longer operating times, a conceptual flowsheet was proposed for a possible process route to recover PGM values circumventing the problematic smelter route for this material.

► This study proposes a flowsheet for extracting PGMs from low-grade concentrates. ► A thermophilic bioleach operating at 65 °C effectively extracted Cu and Ni. ► A subsequent cyanide leach showed promise in extracting Pt, Pd and Rh. ► Concentrate coated on support media and packed in columns simulated heap leaching.