Researchers help gold industry face impurity challenge

As the more traditional gold deposits of the world become depleted, mining companies are facing the challenge of processing ores that contain higher concentrations of other metals.

Helping mining companies find the right way to get the gold out of these trickier deposits is the Parker Cooperative Research Centre for Integrated Hydrometallurgy Solutions (Parker Centre) - an organisation dedicated to finding safer pathways for mineral processing.

Parker Centre CEO Dr Steve Rogers said polymetallic gold deposits contain a greater mix of other metals known as trace elements, which if not managed carefully can be harmful to the environment.

“With the gold industry moving forward with the processing of polymetallic deposits, a better understanding of the complex chemical reactions taking place with these impurities in the gold extraction process is needed,” Dr Rogers explained.

“By knowing how these trace elements behave in the gold extraction process, we can work out how to safely remove and store them.”

To achieve this goal, the Parker Centre has embarked on a research program to understand the many factors that cause metals to dissolve into water-based solutions.

“So far, we have identified the toxic trace elements that get mobilised during the cyanidation of gold ores - the water-based cyanide solution that dissolves gold and other metals out of ore,” Dr Rogers said.

Other preliminary results have shown that mercury contained in certain ores can be absorbed onto the carbon in the carbon-in-leach cyanidation process used by the industry to extract gold from solution. Following this, the mercury can be selectively removed from the carbon during the elution process.

This discovery has provided a pathway to remove mercury from the gold extraction process that prevents further contamination downstream.

“Results like this can lead to technologies that make the mining of polymetallic ores more economically viable and assist in the development of environmental management strategies to manage trace elements,” Dr Rogers said.

Participants include CSIRO, Curtin University, Murdoch University and the University of Queensland and 22 industry participants from the mining and minerals sector.