Cyanide-free future of gold process selection

As legislation in several territories has banned cyanide leaching of gold and the industry has to make due with increasingly refractory ore deposits, the political and financial drivers for alternative leaching methods are becoming ever more pressing. Several advancements have been made in this field regarding new leaching agents, but a novel hydrometallurgical process technology takes time to mature from laboratory scale into a feasible industrial operation. Several different aspects of cyanide-free gold leaching are still under early development – especially compared to cyanide, which has been the dominant method for over a century and is applied worldwide. Simply excluding cyanide from the process does not guarantee the sustainability of the new method, but the overall impact and characteristics of the new processes need to be assessed. In the Research Group of Hydrometallurgy and Corrosion in Aalto University, several different approaches to this topic are being addressed in order to advance sustainable development of cyanide-free gold processing. The three main focuses of this article are (i) process simulation and lifecycle assessment (LCA) of historical, state-of-art and emerging processes, (ii) efficient utilization of existing knowledge through automated decision making tools, and (iii) new innovations in the field. Process simulation and LCA are performed by utilizing HSC simulation and GaBi LCA software for both a cyanide process and a historical non-cyanide chlorination process, so the environmental impacts of the processes can be compared. The decision-making tools discussed are based on case-based reasoning (CBR), which compares new research interests with previously implemented processing options or published research articles. Several process innovations are under way in the research group, but in this article, a novel process of applying nanocellulosic materials in gold recovery is reported.