A golden alternative

US mining giant Barrick Gold has pioneered a unique alternative to cyanide for gold recovery with the help of Australia’s leading research organisation CSIRO.

The world’s largest gold producer is the first to commercialise the environmentally friendly alternative, thiosulphate – a non-toxic chemical used for gold recovery.

With the industry challenged by reducing grades, more complex ores and increasingly tougher regulations?to minimise the environmental impact and risks, the continued research and development will be instrumental for the industry’s future sustainability.

The new thiosulphate leaching process comes off the back of over 10 years’ research and development, with Barrick Gold unveiling the method at its Nevada Goldstrike mine.

The gold miner worked to develop the unique processing method after an increasing amount of ore recovered at the mine was carbonaceous, which doesn’t respond to cyanide without pre-treatment.

The unique process, developed with the help of CSIRO’s ON accelerator program, works by recovering the gold dissolved by thiosulphate using ion exchange resins. Sulphite is then used as an additive to the ion exchange resin for easier separation of the gold, which has traditionally been a challenging process.

Further thiosulfate processes are being developed by CSIRO to work for high-grade gold concentrates, along with in-situ leaching in deep mines and where cyanide is banned or uneconomic.

The broader research is set to help the mining industry closer to home.

CSIRO Mineral Resources Principal Research Scientist Dr Paul Breuer said the research was a vital component in advancing the development of cost-effective thiosulfate- based processes and had the potential to help small mining companies compete against the big mining giants.

Dr Breuer said with increasing public concern and tighter regulations around the use of cyanide, smaller companies were grappling to compete with large corporate miners.

“The use of cyanide is becoming a bigger and bigger hurdle, so it’s closing out more and more of the smaller miners,” he said.

“In WA there used to be quite a large number of small miners back in the 70s and 80s, the government had the mills, and the small miners were able to use these to process their ore.
“That’s all closed down and disappeared, so we see a potential to open up that group of miners again with our research and development.”

Dr Breuer said while the industry was progressing towards cyanide alternatives, it would be some time before we could see thiosulphate processes as a norm and replacing cyanide, especially with the industry’s lucrative sway over WA’s economy.

The gold industry is Australia’s third largest export earner after iron ore and coal, raking in $14 billion in 2014-15.

Around the world, cyanide in gold processing has already been banned in Germany, Czech Republic, Hungary, Costa Rica, some Argentine provinces and in the US states of Montana and Wisconsin, but Australia would need a proven and accessible alternative to cyanide before it could be banned without having a significant impact on the Australia economy.

“The gold industry is very conservative, we have to find those that are keen and have a desire to adopt something new and try it out,” Dr Breuer said.

“It could be some time before thiosulphate-based processes become standard practice.

“Quoted numbers by researchers who have done studies on innovation in the mining industries say it typically takes 15 years to get these at a point where it becomes standard practice.”

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