Copper-gold recovery process is taking off

Chemical giant DuPont has joined forces with New York-listed Newmont to manage a recovery process that promises to transform the copper and gold mining sectors.

The joint venture, called AuGMENT Technologies, will market a new technology that improves the economics of processing gold deposits with high copper contents, and reduces gold losses in primary copper flotation plants.

In addition to producing copper as a pay metal, the technology recovers cyanide for reuse while avoiding cyanide destruction costs.

Five years of research have gone into the development of the process, and the joint venture expects mine-scale production to begin some time in 1996.

In the cyanidization process, the presence of copper in gold deposits reduces recovery, and gold values are often lost in typical copper flotation circuits. The strength of the AuGMENT technology lies in its ability to recover gold and copper profitably, while recycling cyanide back into the leaching process.

Ion-exchange resins are used to pull out the copper-cyanide complex from the pregnant solution. After concentrating the copper-bearing solution, it is fed into an electrowinning cell for processing. Once the copper has been removed, the gold-cyanide solution is treated in a conventional manner. DuPont, the largest producer of sodium cyanide in the world, says the process is environmentally safe in that less cyanide is lost in the tailings.

“We realized the application was much broader than our in-house use,” says Ross Bhappu, manager of economic evaluation for Newmont. “The future was very bright for having a revolutionary impact on the mining industry.” In light of the new possibilities presented by the process, Newmont has changed its exploration strategy.