Recovery of gold and iron oxide from pyrite cinder using reduction roasting, grinding, thiosulfate leaching in the presence of additives and magnetic separation

Abstract

Despite being a common hazardous solid waste, pyrite cinder (PyC) contains valuable metals such as iron and gold, which has attracted considerable research attention. The recovery of gold and Iron from gold-bearing PyC was systematically investigated using an environmentally friendly approach involving non-cyanide extraction and magnetic separation. The results showed that with PyC not subjected to reduction roasting a maximum gold extraction efficiency of 54.7 % was achieved through a copper–ammonia–thiosulfate system. The iron concentrate was assayed at 57.5 wt% Fe with an iron recovery of 83.1 % under optimized conditions. By contrast, a gold extraction efficiency of 67.0 %, as well as a high-quality concentrate with Fe content of 65.1 wt% and Fe recovery of 98.3 %, were obtained via reduction roasting. X-ray diffraction and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy analyses revealed that reduction roasting transformed hematite into magnetite, improving both iron recovery and the quality of the iron concentrate. In addition, reduction roasting generated more porous structures on the particle surfaces, thereby enhancing the gold extraction efficiency. Hence, this study provides new insights into the recovery of Au and Fe from PyC using an environmentally friendly approach.