One-step electrochemical reduction of stibnite concentrate in molten borax

In this study, antimony production from a stibnite concentrate (Sb₂S₃) was performed in one step using a molten salt electrolysis method and borax as an electrolyte. Electrochemical reduction of the stibnite concentrate was performed at 800°C under galvanostatic conditions and explained in detail by the reactions and intermediate compounds formed in the borax. The effects of current density (100–800 mA·cm⁻²) and electrolysis time (10–40 min) on cathodic current efficiency and antimony yields were systematically investigated. During the highest current efficiency, which was obtained at 600 mA·cm⁻², direct metal production was possible with 62% cathodic current efficiency and approximately 6 kWh/kg energy consumption. At the end of the 40-min electrolysis duration at 600 mA·cm⁻² current density, antimony reduction reached 30.7 g and 99% of the antimony fed to the cell was obtained as metal.