A novel sequential heap leach process for treating crushed Platreef ore

Abstract

A novel sequential heap leaching process has been identified as a possible alternative to the conventional concentrate-smelt-refine route for processing Platreef ore, a platinum group metals containing ore with palladium predominance. The present study focuses on testing this process on crushed whole ore, after initial experiments conducted on low-grade Platreef flotation concentrate achieved promising results. Two samples of drill core Platreef ore with size distributions of -25 mm +1 mm and -6 mm +1 mm were first bioleached in cylindrical columns, to simulate heap leaching, at 65°C and then leached with cyanide solution at 50°C in cylindrical columns. Overall the best results were achieved from the tests on the -6 mm +1 mm size fraction sample. After 304 days 93% Cu, 75% Ni and 53% Co were extracted in the bioleach experiment, and after 60 days 57.8% Pt, 99.7% Pd and 90.3% Au in the follow-up cyanide leach experiment. Analysis using a mineral liberation analyser suggested that Pt and Pd were leached mostly from the tellurides while the Pt arsenides appeared resistant to cyanide leaching. From the results it is proposed that the process considered herein is a potential alternative route to treat Platreef ore.

The effect of temperature, cyanide and base metals on the adsorption of Pt, Pd and Au onto activated carbon

“…Several authors have investigated the potential of leaching platinum and palladium with cyanide (Bax, 2004;Bruckard et al, 1992;Chen and Huang, 2006;Huang et al, 2006;Lewins, 2003;McInnes et al, 1994;Mwase et al, 2012Mwase et al, , 2014Shams et al, 2004) and it has generally been found that higher temperatures (N 55°C) are required for the leaching of these metals. The upgrading of the leach solutions through adsorption and elution using activated carbon has been investigated Snyders et al, 2013) and shown to be a possible workable process.…”

Direct leach approaches to Platinum Group Metal (PGM) ores and concentrates: A review

“…Jones (2005) argued that PGMs recovery is typically about 85% in the concentration stage, 95-98% in smelting and 99% in refining. An alternative process to recover PGMs has been proposed by other researchers where PGMs are leached into an aqueous cyanide solution, in which they are solubilized as precious metal-cyanide complexes (Mwase et al, 2014;Chen and Huang, 2006;Aguilar et al, 1997;Trexler et al, 1990).…”

Characterizing the leaching of sperrylite (PtAs 2 ) in cyanide-based solutions

“…A two-stage heap leaching process was developed as an alternative to the conventional concentrate-smelt-refine process to treat Platreef ore (Mwase et al, 2014;Mwase et al, 2012;Eksteen et al, 2012). The process consists of a thermophile heap bioleaching stage which removes large portions of Cu, Ni and Co from the ore for separate recovery and nearly completely oxidises all sulphide present.…”

“…This is followed by a cyanide leach stage at 50°C which intends to mobilise Au, Pd and Pt. The process was tested at laboratory scale using columns to simulate heap conditions (Mwase et al, 2014;Mwase et al, 2012). While the bioleaching stage achieved the desired performance, the cyanide leaching rapidly mobilised Pd quantitatively and 90% of Au, but only 60% of the Pt was extracted over a 60 day period.…”