Researchers remove cyanide from gold leaching process

Currently, the industry is needing higher temperatures, glycine concentrations and oxygen addition levels when leaching gold with glycine in the absence of cyanide.

An eight-year study by Curtin University has led to an improved glycine leaching technology that eliminates the above issues.

It uses a low concentration of a strong oxidising agent known as potassium permanganate, which produced the most successful results compared with other oxidants for the alkaline glycine gold leach system, according to co-research lead and chair for extractive metallurgy for the Future Battery Industries Cooperative Research Centre (FBICRC) Jacques Eksteen.

“Traditionally, leaching or separating gold and other precious metals from an ore deposit or e-waste materials requires the use of cyanide – a highly toxic chemical compound that is known to have detrimental effects to the environment and to the human body,” he said.

“Industrially, it is very expensive to detoxify cyanide, but it still does not eliminate the risks associated with transporting, handling and processing the chemical.”

Cyanide’s toxicity, glycine was naturally produced by the human body, he added.

With low concentrations of potassium permanganate being added to the glycine system, the researchers were able to leach 85.1 per cent of gold from the ore deposit at ambient temperature.

Co-research lead and senior research fellow Elsayed Oraby said researchers at Curtin University had spent years developing a new leaching process, and their work broadened the use of this patented technology, making it more suitable for extracting gold deposits.

“We believe this new process will bring many benefits to gold extraction industries, which from an environmental point of view, is a much friendlier extraction method,” he said.

The Curtin team is now working with Mining and Process Solutions to commercialise the process.