Synergistic recovery of copper, lead and zinc via sulfurization-reduction method from copper smelting slag

Cu, Pb and Zn were synergistically recovered from copper smelting slag via the sulfurization-reduction method. Pyrite was used as the sulfurizing agent to selectively sulfurize and recover valuable metals lost in the slag in the reductive atmosphere. Thermodynamic analysis and laboratory experiments were carried out to determine the feasibility and reliability of this process. The optimal experimental conditions were defined as follows: a dosage of sulfurizing agent (pyrite) of 26%, 6% coke addition of copper smelting slag mass, and smelting at 1350 degrees C for 3 h. Under the optimum conditions, Cu, Pb and Zn recoveries were 97.58%, 89.91% and 98.20%, respectively. Cu, Pb and Zn contents in the cleaned slag were 0.10%, 0.01% and 0.38%, respectively. The matte contained 7.28% copper. The proportions of Zn entering the gas, slag and matte phases were 80.93%, 10.09% and 8.98%, respectively. The proportions of Pb entering the gas, slag and matte phases were 40.12%, 1.79% and 58.09%, respectively. The matte phase mainly comprised Cu8S5, FeS, and some metals, such as Cu, Pb and Fe. Fe3O4 in the slag was reduced from 19.50% to 2.97%.