Abstract
Microwave technology has been confirmed to be suitable for use in a wide range of mineral leaching processes. Compared to conventional leaching, microwave-assisted leaching has significant advantages. It is a proven process, because of its short processing time and reduced energy. The purpose of this study was to enhance the gold content in a refractory gold concentrate using microwave-assisted leaching. The leaching efficiencies of metal ions (As, Cu, Zn, Fe, and Pb) and recovery of gold from refractory gold concentrate were investigated via nitric acid leaching followed by microwave treatment. As the acid concentration increased, metal ion leaching increased. In the refractory gold concentrate leaching experiments, nitric acid leaching at high temperatures could limit the decomposition of sulfide minerals, because of the passive layer in the refractory gold concentrate. Microwave-assisted leaching experiments for gold recovery were conducted for the refractory gold concentrate. More extreme reaction conditions (nitric acid concentration > 1.0 M) facilitated the decomposition of passivation species derived from metal ion dissolution and the liberation of gangue minerals on the sulfide surface. The recovery rate of gold in the leach residue was improved with microwave-assisted leaching, with a gold recovery of ~132.55 g/t after 20 min of the leaching experiment (2.0 M nitric acid), according to fire assays.
Highlights
Gold has excellent physical and chemical properties, and is one of the most important noble metals
The recovery rate of gold in the leach residue was improved with microwave-assisted leaching, with a gold recovery of ~132.55 g/t after 20 min of the leaching experiment (2.0 M nitric acid), according to fire assays
Microwave-assisted leaching experiments for gold recovery were conducted for the refractory gold concentrate for different reaction times
Summary
Gold has excellent physical and chemical properties, and is one of the most important noble metals. The current rapid decline in high-grade gold ores and readily available low-grade gold ores has made the mineral processing industry increasingly reliant on complex and refractory gold ores [1,2]. Mineral processing challenges related to the complexities of ore mineralogy and the process parameters, such as the impacts of associated minerals, are important research questions [3]. Mineralogical studies aim to characterize complex sulfides and show the interrelations of the target minerals in the refractory minerals. These studies usually analyze gold-bearing sulfide minerals for follow-up processes and efficient gold recovery. Gold can be found in complex sulfide minerals, due to the presence of invisible gold, and due to the existence of solid solutions [4]
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