CSIRO is working to increase gold recovery, reduce reagent consumption and develop non-cyanide processing for gold operations in Australia and throughout the world.
In terms of size, Australia’s gold industry is the second largest in the world behind South Africa. The industry is Australia’s fourth largest export earner, worth between A$5 billion and A$6 billion annually.
Extracting gold from ores
Gold is commonly extracted from ore using the carbon in pulp (CIP) process.
The gold-bearing ore is crushed and ground to approximately 100 microns. Lime, cyanide and oxygen are then added to the ground and slurried ore.
The lime raises the pH, while the oxygen and cyanide oxidise and complex the gold.
To recover the dissolved gold, pellets of activated carbon are added.
The gold adsorbs to the carbon and the carbon is moved up the leach circuit achieving gold loadings of approximately 2 500 grams per tonne.
The loaded carbon is removed from the front of the adsorption circuit by screening the coarse carbon pellets.
These carbon pellets are transferred to an elution circuit where the gold is washed from the carbon using a hot caustic cyanide solution.
Gold is electrowon from the concentrated gold solution onto steel wool with the steel wool being dissolved away by hydrochloric acid, leaving a gold doré which is smelted into bars for shipment to the mint.
Challenges for the gold industry
To remain profitable, the gold industry needs to improve processes and develop new ways of processing lower-quality ores and tailings.
The gold industry is Australia's fourth largest export earner, returning between A$5 billion and A$6 billion annually.
Environmental issues are a concern, particularly in light of the high levels of cyanide used in the extraction process.
Non-cyanide alternatives need to be found to minimise environmental and safety impacts in appropriate situations.
Research areas
CSIRO is currently conducting research in the following areas, in collaboration with the Parker Cooperative Research Centre (CRC) for Integrated Hydrometallurgy Solutions:
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flowsheeting and process modelling
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characterising and preparing ores for leaching
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processing complex ores
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non-cyanide leaching and recovery of gold.
Read more about research in the following areas:
New CSIRO-developed analytical methods have helped the Cowal Gold Mine become the first operation in Australia to comply with the gold industry’s International Cyanide Management Code.
A sequential elution process could change the way gold is eluted from carbon, simplifying mercury recovery.
Research focused on carbon management and the impact of impurities on adsorption circuits can potentially help the gold industry improve efficiency and reduce gold solution losses.
Process models enable the hydrometallurgical industry to capture the existing knowledge base, identify areas where knowledge is lacking and understand the impact of circuit changes.
An unfortunate twist of chemistry means that one of the earth’s most beautiful metals requires one of the planet’s most deadly compounds to extract it from an ore body - gold mining relies on the use of cyanide to dissolve gold into solution so it can be recaptured as pure metal.
Find out more about the work of CSIRO Minerals.
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