Thiosulphate-based solution replaces cyanide in gold recovery test

Thiosulphate-based solution replaces cyanide in gold recovery test at Menzies Gold Hub


Experts have successfully validated thiosulphate’s ability to serve as a non-toxic replacement for cyanide in gold recovery. The recent demonstration project at the Menzies Gold Hub showcased the solution’s capacity to operate in-field and at scale. Previously, thiosulphate had only undergone laboratory test work.

Thiosulphate is an inorganic compound, a salt, which is non-flammable and water soluble. Although similar compounds exist, Clean Mining, in partnership with Australia’s CSIRO, have created an application specific for a range of ores for different mining operators.

Managing Director Jeff McCulloch said that “one of the key performance indicators” in this project was to reach a benchmark of over 80% recovery of leachable gold. The Menzies project led to an 85% gold recovery rate.

The project focused on:

  • designing, building, and transporting the plant to Menzies from Perth (a distance of 730km)
  • carrying out optimised procedures and eliminating cyanide use
  • processing ore and using the CSIRO IP in an innovative new leaching process
  • smelting and forming gold into bars

This project, McCulloch said, has allowed for continued analysis and learnings. For example, the introduction of agitated tanks, as opposed to the previously used vat leaching tanks, has resulted in even greater recovery rates. As such, these will be incorporated in future project planning.

“This leach process design also demonstrated how a small mobile plan could operate in this field with the ability to unlock small/high grade stranded deposits,” the executive said.

This 2019 year, in particular, has seen increased interest in the development of thiosulphate-based solutions from producers who want to ensure sustainable and responsible mining, and who want to avoid the compliance and rehabilitation costs associated with cyanide.

The company behind this project, Clean Earth Technologies, is looking for opportunities to transform gold mining by eliminating the use of toxic chemicals to recover gold, offering environmentally and socially responsible solutions for clean mining worldwide

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