Processing of Küre (Turkey) copper slag for the recovery of copper and cobalt and the production of γ Fe₂O₃

In this work, processing of the copper slag generated over a period and stockpiled at Küre, Turkey, has been investigated for the recovery of copper and cobalt and the production of magnet grade iron oxide. This fayalitic slag analysing about 0.8% Cu and 0.4% Co is reduced with coke/graphite in a D.C. arc furnace to yield a liquid alloy rich in iron and containing about 3.8% Cu, 3.3% Co and 2.1% S. The alloy is granulated and leached repeatedly with hot sulphuric acid so that cobalt and iron are solubilised leaving behind copper and the impurities in the residue. The leach liquor is treated with H₂S to precipitate cobalt as the sulphide. The remaining liquor containing chiefly FeSO₄ is taken through a processing sequence consisting of geothite precipitation, dehydration, controlled reduction, and finally, reoxidation to obtain γ Fe₂O₃ with coercivity value in the range of 330-380 Oe.