A modified sulfation-roasting-leaching process for recovering Se, Cu, and Ag from copper anode slimes at a lower temperature

Abstract

Copper anode slimes are source of valuable elements such as selenium, tellurium, copper, silver, lead, antimony, tin, gold, and platinum group metals. There are vast, diverse methods to recover precious elements from the copper anode slimes. Sulfation roasting is one of the prevalent methods that became widespread because of the simplicity of the technology and available knowledge of the process. High energy consumption and too many stages that produce gaseous and liquid effluents in each stage are the main drawbacks of this approach. In this study, the conventional sulfation roasting approach was environmentally modified to a lower temperature sulfation-roasting-leaching process by reducing the temperature from 600 to 800 °C to ca. 247 °C. Therefore the energy consumption is lowered significantly and the number of stages is shortened to 2 separate stages of sulfation-roasting and leaching as the main stages of the process. In this regard, the gaseous and liquid effluents of the process are reduced and therefore, the environmental drawbacks decreases. The effects of the two parameters of temperature and liquid to solid ratio were investigated using response surface methodology. At the optimum condition, temperature of ca. 247 °C and L/S ratio of 1.95, 99.93% of selenium, 96.53% of copper, and 96.48% of silver were recovered. After separation of selenium, copper and silver were taken apart by solvent extraction using CP-150. Using 10% (V/V) CP-150 in kerosene, a 5 min contact time, pH of 4 and organic to aqueous ratio of 1, 99.87% of copper was extracted.