The improved tests are faster and less
labour intensive - making gold processing
easier.
Image: iStockphoto

A new method of testing for cyanide in gold processing is providing new levels of effectiveness and has seen Australia’s first mine that is able to comply with the International Cyanide Management Code (ICMC).

A team at CSIRO’s Parker Centre, led by Doctor Paul Breuer, is using high-performance liquid chromatography (HPLC), to condense multiple labour-intensive tests into one process.

"In the past, when gold production first started, a lot of the operations were treating the oxide ore, which is simple. It’s easy to mill, you don’t need much cyanide because there’s nothing else reactive in there, the gold leaches out and you can recover it without too much trouble,” says Dr Breuer.

The National Pollutant Inventory requires gold miners to know where cyanide is going to in the process and any discharge to the environment. At the moment, estimation is used where full testing data is unavailable.

“The chemistry behind the reactions of these minerals is complex and poorly understood,” Dr Breuer says.

“As all that ore has been treated, they’re now looking at what else they can treat, and as you go further down you come into the sulphide minerals. These are the ones that react with cyanide, so your cyanide and oxygen consumption goes up.”

By trying different eluent compositions and methods of separating anions, Dr Breuer’s team managed to condense the cyanide tests.

The new testing method has enabled the Cowal Gold Mine in NSW to become the first operation in Australia to comply with the gold industry’s ICMC, as well as contributing to understanding of the chemical reactions involved.

While the testing is still confined to the laboratory, improvements are taking place in the field.

“Previously there were HPLC techniques where you could quantify the free cyanide but you couldn’t measure the metal cyanides at the same time,” says Dr Breuer.

“Some of our clients have already used our information to optimise their reagent addition.”