Joined: 01 May 2011
|Posted: Tue Sep 11, 2018 2:06 am Post subject: A Greener Shade of Gold
|A Greener Shade of Gold
By Robert Hobson (Australia)
A new method of extracting gold could eliminate the need for toxic chemicals to be used in the extraction process and give small and medium-sized producers an edge over larger competitors. Developed through a joint project involving Australia’s national science agency – the Commonwealth Scientific and Industrial Research Organization – and local firm Eco Resources Research, the method involves using a non-toxic alternative called thiosulphate in place of cyanide to dissolve or ‘leach’ the gold from processed ore in to a liquid solution. It is then further treated to reclaim the gold particles.
CSIRO Mineral Resources’ principal research scientist Paul Breuer said the method also eliminates the risk of contamination when disposing the waste materials – called tailings –from the separation process. “Tailings disposal will still require the usual approvals, but there will be no potential for toxic solution run-off or seepage, and no need for any tails treatment before discharge as is often in the case today for cyanidation plants”, he said. He also said: “Process economics in most cases will also drive leach solution recovery…and which will leave only low levels of residual reagents in the tailings.”
Eco Resources Research poured its first ingots last month in a demonstration plant in Menzies, Western Australia and hopes to become the country’s first ‘cyanide-free’ producer. Managing director Paul Hanna said this was a major milestone and a “fantastic achievement”. There is a possibility for the method’s application in extracting other metals, like silver and copper, but this is contingent on other minerals that make up in the ore as these metals cannot be extracted from particular types of minerals.
Several countries including Germany, the Czech Republic, Hungary and a number of South American and US States have banned or limited the use of cyanide in response to environmental and health concerns from ecological disasters. One example in the Asia Pacific region is the contamination of the Ok Tedi and Fly river systems in Papua New Guinea, where the Ok Tedicopper-gold mine discharged about 2 billion tonnes of untreated mining waste into the Ok Tedi river between 1984 and 2013.
Another advantage of the new method is cost, as smaller producers may struggle to find $AUD30 million for a cyanide-based processing plant but could afford to invest in a thiosulphate-based system for about $AUD2.5 million. The CSIRO also aims to develop the system further by making it mobile to make scattered gold deposits economically viable and used in jurisdictions where cyanides are banned or cannot be used. “Within this (space) there is a market opportunity for mobile plants using this technology to unlock stranded small high-grade deposits,” Breuer said. “As the industry gains confidence with more plants adopting the technology, we anticipate significant growth and demand.” He also said negotiations are in place to commercialise the technology and make it available overseas.
CSIRO chief executive Larry Marshall described the developments as a “game-changer for small producers or those looking ahead of increasing market demand for greener commodities.” “Early industry trials like this are critical to innovation and get to the heart of CSIRO’s mission to tackle big, real-world challenges and unlock a better future for everyone.”