Metals extraction strikes gold

Materials World magazine
1 Oct 2008
Sample of a sulphide ore containing gold

A sulphide reduction process (SRP) that enables ‘fast and cheap’ extraction of gold from sulphide ores is available from Haber Inc, based in Arlington, USA.

Most gold extraction uses toxic chemical leaching involving mercury or cyanide. The SRP approach does not use such chemicals and allows the company to work with sulphide ores, one of the most common sources of gold in the world.

It builds on the Haber gold process (HGP), which could only be used on oxide ores as the presence of sulphide inhibited its extraction rate. The SRP works with the HGP and Haber’s ‘Aladdin’ ore processing machine.

Although the company has not revealed the chemical composition of its water-based solution, it has made some strong claims about the technique. The SRP is said to have an extraction efficiency of 97%, and produces gold powder with purities of 98.8%. The system is also cheap compared to other extraction methods, says Albert Conti, President and Chief Operating Officer of Haber. ‘In ore with a low-sulphur content, it probably costs us US$1 per tonne to process. There is nothing I know of that is cheaper.’

Speed of extraction is another area that Conti says cannot be beaten. ‘We have been testing sulphide ores and are able to do the entire process, from sulphur reduction, extraction and recovery to powdered gold, in an hour and a half. That same material would take 36 hours with cyanide, which only gets an 83% extraction efficiency. We’re between seven to 25 times faster.’

One of the other benefits of the process is its environmental credentials. ‘If you look at artisanal miners, they are using mercury to amalgam gold in alluvial deposits. They pour mercury over the gold particles and burn it off, which destroys their health and leaves them with an impure piece of gold that has silver and copper in it,’ says Conti. Haber’s chemicals are said to be safe enough to drink (something Conti has done during demonstrations). He believes the impact this technology could have on small and medium-sized miners is immense.

The Aladdin machine is at a pilot size, and can only handle loads up to 200lbs. However, because it is a chemical-based solution, Conti says it should be simple to scale up. ‘It has been a major engineering effort over the last four years to devise new equipment and formulations for recovery and sulphide recovery, but we’ve got it to a point where we can comfortably handle commercial sizes,’ he says.

The company is currently seeking funding for larger equipment through joint-venture partnerships. Haber has no intention to patent or sell its technology, but instead wants to keep it in-house, accepting ore loads for processing.

Further information

Haber Inc