China Nonferrous Metallurgy

The large volumes of offgas dust generated from copper pyrometallurgical processes contains arsenic and multiple valuable metals, a potential environmental hazard but important secondary resources at the same time. The approaches of recovering resources from the smelter dust are mainly: hydrometallurgical, pyrometallurgical, and combination. In the pyrometallurgical approach, impurity elements and metal values are selectively separated through oxidizing roasting (smelting) or reducing roasting (smelting). Such processes are short, capable of treating large quantities of dust, and low in capital costs, but at the same time have several disadvantages: low metal recovery, high overall energy consumption rate, large quantities of waste, and heavy environmental impact. The hydrometallurgical processes include acid leaching, alkaline leaching, and water leaching. Comparatively acid leaching is more developed, and numerous in industrial applications. However, acid leaching also generates large amounts of residue which requires treatment. The combined processes are mainly a combination of hydro and pyro metallurgical process or of mineral processing and metallurgical treatment. Such a combined approach has salient advantages when treating smelter dusts of complex composition in terms of elements and substances. These processes have good arsenic removal performance, and allow the recovery of multiple metal values including copper, zinc, cadmium, lead, bismuth, antimony, indium, but is also long in process flow and high in capital costs.