Feasibility of Electro-Reduction of Metals in Sulfide-Based Copper Removal Slag for Steelmaking

This paper proposed an innovative electrochemical method for copper recovery from spent sulfide slag (Na₂S-FeS-Cu₂S), generated during copper removal from iron-based melts. It aims to reduce the high decopperization agents' consumption caused by low copper distribution ratio during the copper removal process, address the cost issues by recycle of slag and recovery of copper, and expand the application potential of the emerging copper removal method using the sulfide slag systems. The feasibility of electro-recovery of copper is verified by cyclic voltammetry tests and potentiostatic electrolysis experiments. The results show that in the Na₂S-FeS-Cu₂S melt, although copper cannot be reduced alone without reducing iron, rough separation can be achieved by controlling the temperature. The current efficiency of Cu⁺ reduction in the molten sulfide is about 9.1% due to electronic conduction in the sulfide melt, which needs further improvement. The slag treated by the innovative electrochemical process can be reused, as the XRD results show that it has a similar composition to the primary slag unused.