Green and efficient utilization of waste ferric-oxide desulfurizer to clean waste copper slag by the smelting reduction-sulfurizing process

Abstract

This research proposed an efficient, innovative and environmentally friendly technology named smelting reduction-sulfurizing process, which uses one waste (waste ferric-oxide desulfurizer) to treat another (waste copper slag). In the new process, the waste ferric-oxide desulfurizer was employed not only as a sulfurizing agent to sulfurize and collect the copper lost in copper slag, but also as a reductant to reduce the magnetite to “FeO” and thus improve slag fluidity. It was revealed that 90.81% Cu was recovered and enriched in copper matte under the smelting conditions. The matte contained 15.87% copper, 20.25% S and 49.56% Fe, which can be returned to the copper smelting process as a feeding. Meanwhile, the removal rate of hazardous elements, such as Ni, Pb, Zn, As, Sb, Bi and Hg, from the initial copper slag by the new process was also determined, and the elimination rate of those elements was all over 90%.The leaching toxicity was used to further evaluate the environmental impact of the cleaned slag, indicating that the concentrations of toxic element ions in the leachate are all much lower than the thresholds, which confirmed that the cleaned slag with trace toxic elements is safe and harmless.