Green Gold Production from Primary and Secondary Resources

Abstract

The exceptional chemical resistance of gold is a significant property of this precious metal, but it can pose challenges when it comes to gold extraction. Many metallurgical processes rely on highly aggressive or toxic reagents, and artisanal and small-scale gold mining activities, in particular, have faced criticism due to their difficult-to-control environmental impact. With growing ecological concerns, society and industry are compelled to seek efficient gold recovery methods that replace the use of mercury or cyanide. Over the past decades, extensive research has been conducted on alternative leaching reagents, showing promising technical and environmental characteristics. Various demonstration and pilot-scale application tests worldwide have provided valuable insights for potential industrial implementation. However, to date, only one industrial-scale application using the cyanide alternative thiosulfate has been reported. Apart from chlorination or aqua regia in refineries and recycling specific waste streams, there is a lack of notable industrial applications for cyanide alternatives, particularly in gold recycling from secondary resources. This is significant as it could have a substantial ecological impact by reducing the need for mining activities. For instance, electronic waste, which is increasing in volume and importance, represents a resource for gold recovery but lacks an efficient decentralized process. This work discusses the potential of cyanide alternative reagents for industrial application in gold production and recycling, while exploring various factors that contribute to the limited acceptance among gold producers.