SBIR Phase II: An Economic, Sustainable, Green, Gold Isolation Process

The broader impact/commercial potential of this Small Business Innovation Research Phase II project is the potential to change the way gold mining is carried out by improving the process economics and reducing the environmental impact of mining operations. Current gold isolation methods involve the consumption of vast quantities of sodium cyanide, where cyanide is contained in large tailing dams, posing an environmental threat as exemplified by documented breaches. In the United States there are gold deposits which have not been exploited because of technology limitations and environmental concerns. The technology being developed in this project will improve the profitability of existing mines, as it can be employed with only minor changes in plant design. It will also but will also lead to new jobs. Another opportunity is to extract gold from copper tailings dams. The proposed technology will potentially make cleanup of these sites profitable and can be applied worldwide. In the longer term, the process could be adopted in third world countries which still rely on mercury which pollutes, not only the environment, but also the food chain. The objectives of this Phase II research project are to (i) scale up the extraction of gold using both the heap and vat leach processes, (ii) optimize the crystallization of Au(III) in the presence of the natural product á-cyclodextrin, and (iii) isolate the gold. For heap leaching, it is proposed to operate at the 400-MT level, concentrate the gold salt and crystallize the gold-cyclodextrin complex. Scale-up will require designing the process to utilize existing equipment (built originally for the sodium cyanide process) and introducing new chemicals. For vat leaching, a small pilot system will be built to accept crushed ore as the feed, and the resulting gold-containing extract will be taken through the crystallization process. Optimization of the leaching agent, mass transfer, kinetics and materials consumption will be ongoing. Regulatory approval for vat leaching, once secured, can be applied on-site globally to demonstrate the environmental and economic benefits of the process. This technology has the potential to significantly make existing and new mining operations more environmentally sustainable.