Direct electrochemical reduction of copper sulfide in molten borax

In this study, for the first time, direct copper production from copper sulfide was carried out via direct electrochemical reduction method using inexpensive and stable molten borax electrolyte. The effects of current density (100–800 mA/cm²) and electrolysis time (15–90 min) on both the cathodic current efficiency and copper yield were systematically investigated in consideration of possible electrochemical/chemical reactions at 1200°C. The copper production yield reached 98.09% after 90 min of electrolysis at a current density of 600 mA/cm². Direct metal production was shown to be possible with 6 kWh/kg energy consumption at a 600 mA/cm² current density, at which the highest current efficiency (41%) was obtained. The suggested method can also be applied to metal/alloy production from single- and mixed-metal sulfides coming from primary production and precipitated sulfides, which are produced in the mining and metallurgical industries during treatment of process solutions or wastewaters.