Electrochemistry of Molten Sulfides: Copper Extraction from BaS-Cu₂S

The electrolytic extraction of liquid copper at 1105°C from a molten sulfide electrolyte composed of 57 wt% BaS and 43 wt% Cu2S was investigated. DC cyclic voltammetry, Fourier transformed AC voltammetry, and galvanostatic electrolysis revealed that the electrodeposition of copper is possible in the selected molten sulfide electrolyte. The half wave potential for the reaction on graphite was determined, and liquid copper of high purity was obtained by galvanostatic electrolysis. These preliminary results confirm that molten sulfides free of alkaline elements could be used as an electrolyte for faradaic applications, despite the semi-conducting nature of the melt. In addition to demonstrating the need for enhanced understanding of the transport properties of such electrolyte, the results show the critical impact of the cell design to improve the process faradaic efficiency.