A new cheaper method for recovering low grade platinum metals has been found.
Research at the Western Australian School of Mines, in collaboration with South Africa’s Stellenbosch University, has shown that the traditional smelting methods can now be replaced with low cost direct leaching, according to Science WA.
The process now opens up deposits that were considered too small to extract using conventional smelting and refining methods.
The Munni Munni PGM deposit in the Pilbara, Panton in the Kimberley, and Fitfield in Central New South Waled – Australia’s largest platinum group metals deposits – were not “large enough to support the capital costs of building a smelter,” Curtin University chair of extractive Metallurgy professor Jacques Eksteen said.
“In WA, for instance, the deposits are just too far out…the logistical costs would kill you.”
“PGMs tend to form a complex range of minerals, we’re talking about 30 to 40 different minerals, and they each have different resistance to leaching, making it hard to find a unique solution for all deposits,” Prof Eksteen says.
However by using direct leaching “we found we could recover economic levels of platinum metal, then we were able to recover it from solution,” Eksteen said.
The leaching itself is a two stage process that uses biological leaching to remove the copper and nickel typically found in platinum group metal deposits, and then using cyanide to extract the PGMs.
Following this the metals are adsorbed from the solution using activated carbon, and then eluted from the carbon in a concentrated form, after which they can be released one by one.
Further research is now focused on developing reagents for improved recovery rates and higher selectivity.