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.

Australia-based Parker Cooperative Research Center for Integrated Hydrometallurgy Solutions, a cooperative research organization specializing in mineral processing studies, said it is helping mining companies find the right way to get the gold out of these trickier deposits.

Dr. Steve Rogers, Parker Center CEO, said polymetallic gold deposits contain a greater mix of trace elements. If not managed carefully, trace elements 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,” Rogers said.

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

To achieve this goal, the Parker Center 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 mobilized during the cyanidation of gold ores—the water-based cyanide solution that dissolves gold and other metals out of ore,” Rogers said.

Other preliminary results have shown that mercury contained in certain ores can be absorbed onto the carbon in the Carbon In Leach (CIL) cyanidation process used by the gold industry to extract gold from solution. Following this, the mercury can be selectively removed from the carbon during the elution process, enabling the separation of gold over mercury.

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,” Rogers said.

Other Parker Center research is investigating alternative reagents to cyanide such as thiosulfate and iodine/iodide systems that are showing promise in extracting gold from less common styles of mineralization.

The Parker Center comprises four core research participants—CSIRO, Curtin University, Murdoch University and the University of Queensland—and 22 industry participants from the mining and minerals sector.