A novel process to upgrade the copper slag by direct reduction-magnetic separation with the addition of Na2CO3 and CaO

Abstract An innovative technology for direct reduction-magnetic separation with the addition of Na 2 CO 3 and CaO was studied to upgrade copper slag assaying 40.33% Fe total and 0.65% Cu. It is difficult to recover iron and copper from the slag by direct reduction since the iron mainly occurs in fayalite and the copper exists in copper sulfide. Additives such as Na 2 CO 3 and CaO has been proven to be capable of reinforcing the reduction of refractory iron ore in many papers. In this study, the effect of Na 2 CO 3 dosage and binary basicity (CaO/SiO 2 ) on the coal-based reduction of copper slag was investigated. The results show that the addition of CaO at 0.5 basicity and 8% sodium carbonate, the recovery of the iron and copper can be significantly improved to 94.3% and 86.5%, respectively. Meanwhile, the iron and copper content of magnetic concentrate are maintained at 90.5% and 1.2%, respectively, which can be used as burden for smelting of weathering steel, and the nonmagnetic tailings obtained in this process can be applied as raw materials in cement and industry, and the dust collected from the direct reduction process contains 50.65% Zn and 8.56% Pb at a recovery of 99.16% and 91.89%, and can be used as feed for extraction of Zn and Pb.