Use of sulphur dioxide as reducing agent in cobalt leaching at Shituru hydrometallurgical plant

Cobalt oxide minerals in copper oxide ores from the Gécamines concession in the Democratic Republic of Congo are effectively leached using a sulphuric acid solution. This study aimed to explore the use of sulphur dioxide as a reducing agent for cobalt III during the leaching process. The methodology involved laboratory tests conducted at 40°C and pH 4.05, where cobalt-rich ores were finely ground and mixed with spent electrolyte. Preliminary results indicated that sulphur dioxide could serve as a viable alternative to traditional reducing agents like sodium metabisulphite and copper powder, significantly affecting the overall operational costs associated with cobalt production. Subsequent plant trials at the Shituru hydrometallurgical plant confirmed these findings, demonstrating that by utilizing sulphur dioxide, a selective leaching process could be established, allowing for the separate dissolution of cobalt under reducing conditions, followed by copper dissolution under oxidizing conditions. This modified copper-cobalt flow sheet presents an innovative approach to enhancing the efficiency and cost-effectiveness of cobalt extraction processes. The results underscore the potential for sulphur dioxide to optimize operational efficiencies within hydrometallurgical practices.