Australian researchers have found a way to produce gold without using cyanide for the first time.
The country’s government-backed research organisation, the CSIRO, reports that the new process uses a chemical called thioshulphate, which greatly reduced the environmental risks and costs associated with gold production.
It has been working with US gold miner Barrick to develop the process
Cyanide is, of course, highly toxic and a potential environmental hazard…Thiosulphate has long been seen as a potential alternative to cyanide for liberating gold from ores, but it has proved difficult to master – until now. Thanks to the new process, which incorporates patented technology we’ve developed with Barrick, the company will be able to process and profit from four million tonnes of stockpiled ore that was uneconomic to process by traditional methods.
As part of the thiosulphate process, gold-bearing ore is heated in autoclaves and pumped as a thick slurry of ore, air, water and limestone into the new “resin-in-leach” circuit that takes place inside large stainless steel tanks.
There the slurry interacts with thiosulphate and a fine, bead-like substance called resin that collects the gold.
At full capacity, 13,400 tons of ore can be processed daily, with leaching taking place simultaneously in two sets of seven tanks.
Bill Condie is a science journalist based in Adelaide, Australia.
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