A natural extraction technique for low-grade copper is being tested for its potential to maximise recovery rates and extend mine life.

The research project from Flinders University in South Australia is focused on exploiting a normal ore body procedure known as supergene enrichment.

Supergene enrichment is a natural process that occurs at copper deposits close to the surface where the circulation of groundwater takes the primary sulphide minerals and redistributes it into copper metal.

Lead researcher and Flinders University Professor of Chemical Mineralogy Allan Pring said low-grade ore was often ignored because it was not seen as economically viable.

He said his research aimed to optimise the amount of minerals recovered at a mine site and reduce waste.

“What tends to happen is a small amount of ore, about 10 to 15 per cent, ends up in the tailings and waste piles and you don’t get all the metal out of the copper ore,” he said.

“If you could get that material out in a cost effective way then you would not only maximise the amount of copper but the extra copper could be worth millions and millions.”

This process has been seen at the historically important copper deposits in South Australia, including Burra, Kapunda and Moonta, which helped to establish the state’s economy in the 19th century.

The research project will test the effectiveness of supergene enrichment at Flinders’ laboratories using special flow-through equipment developed at the university.

Professor Pring said he hoped to scale up to real-world tests within three years.

“We have been doing these experiments on other systems, making primary sulphide for the last decade and my research group is the world leader in this area. This seemed like a good way forward to see if we could apply it to ore deposits as well,” he said.

The Flinders researchers, including Associate Professor Sarah Harmer, Dr Christopher Gibson and postdoctoral researchers, will collaborate with leading mineralogy researchers Professor Joel Brugger (Monash University) and Dr Benjamin Grguric (South Australian Museum), along with BHP Billiton principal geometallurgist Dr Kathy Ehrig.

“We are not setting out to improve the recovery of copper by a few percentage points. We are aiming to provide a new and innovative approach to the problem,” said ARC Future Fellow Associate Professor Harmer, who is studying the interaction between bacteria and mineral surfaces using advanced synchrotron spectromicroscopy techniques.   

“Mild oxidizing reactions take place causing the primary ore minerals, such as chalcopyrite, to be replaced by more copper-rich, less refractory minerals,” she said.

“These processes are driven by coupled dissolution-reprecipitation (CDR) reactions and in many CDR reactions, the reaction mechanism, rather than intensive properties such as pressure and temperature, control the nature of the products and the overall reaction process.

The success of this project would not only extend the life of jobs and infrastructure at remote mine sites but reduce spending on the development of new mine sites.

The Australian Government has provided $485,000 in funding for the project through the Australian Research Council’s Linkage Projects scheme with an additional $300,000 being provided by BHP Billiton.

Flinders University researchers are also involved in the 2016-2020 ARC Research Hub for Australian Copper-Uranium project.

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