Flowsheet design and environmental impacts of cobalt co-product recovery from complex Au-Co ores

The increasing demand for battery metals, such as cobalt, increases the attractiveness of conventionally overlooked raw materials, such as small multi-metal deposits. With the length of mining and extractive metallurgy projects, it is advantageous to evaluate possible processing routes well in advance with a variety of tools, such as experimental, piloting, simulation, and life cycle assessment. In this study, simulation-based life cycle assessment was used to compare the baseline of only recovering gold from sulfidic Au-Co-(Cu-As) ores to five scenarios where both gold and cobalt were recovered, the latter as battery grade cobalt sulfate heptahydrate. Technical performance and several impact categories affecting climate change, ecosystems, and human health, were investigated to assess the advantages and drawbacks of each option. The environmental competitiveness varied between different studied scenarios vs. observed impact categories. The baseline process - with no cobalt recovery - had the lowest energy and global warming impacts but fared worse in toxicity categories. Pressure leaching scenario achieved low toxicities but was shown to be environmentally highly intensive in all other categories. The pyrometallurgical-hydrometallurgical roasting-leaching process resulted in the lowest environmental impacts in most of the studied categories. However, in terms of acidification and photochemical oxidant creation, the fine grinding-leaching process was the best option. In all studied scenarios the major technical challenge was found to be the stabilization of arsenic, yet the technical issues can effectively be resolved by treating the arsenical and non-arsenical concentrates in separate processes. In the current results, the temporal boundary, allocation choice, and current lack of experimental work remain major sources of uncertainty.