Using a direct-current arc furnace to recover cobalt from slags

Cobalt can be recovered from a variety of slags by treatment with a carbonaceous reducing agent in a direct-current arc furnace at around 1,500°C. The principal materials suitable for treatment using this technology are primary smelter slags, which typically originate from the processing of sulfide concentrates. The technology has been tested using copper, nickel-copper, and lead smelting slags. In all cases studied, cobalt is recovered as a valuable by-product to help improve overall plant profitability. Pilot-plant tests have demonstrated a cobalt recovery of more than 80 percent at power levels up to 600 kW. Very high recoveries of other valuable elements, such as nickel and copper, have also been achieved.