Optimizing Gold Recovery from Witwatersrand-Type Ores Using Alkaline Glycine Leaching and Conditional Simulation

Abstract Witwatersrand-type gold deposits in South Africa are generally amenable to cyanidation due to their free-milling nature. However, the relatively easy-to-process gold ores have been mostly depleted, and the remaining ores are of low-grade combined with semi-refractory properties. Here, we use an integrated approach to understand the mineralogical and textural characteristics of the Witwatersrand-type gold ores and to explore the effectiveness of glycine-leaching gold recovery. Analysis of sulfide minerals using 3D micro-X-ray computed tomography data shows these minerals can be used as predictive indicators for feed gold grade as they either co-exist and/or encapsulate gold. Primary experimental results demonstrate that alkaline glycine can recover > 80% Au in 100 hours at ambient temperatures. Glycine thus holds promise for gold recovery of low-grade free-milling and semi-refractory Witwatersrand-type gold ores. We also note that the presence of carbonaceous matter in ores, such as in the Black Reef orebody, adversely affects gold recovery. Ore blending may therefore be a suitable option to remediate poor gold recovery. Lastly, we demonstrate that stochastic simulations and data analytics can help augment primary experimental data to estimate uncertainty, providing a better understanding of experimental results, and thus providing future research directions.