Separation of Zinc from Zinc Ferrite by Magnetization Roasting and Ammonia Leaching

Zinc ferrite can be found in zinc-bearing dust in ironmaking and steelmaking. It is difficult to be recovered due to its stable properties. The magnetization roasting and ammonia leaching method were used to separate iron and zinc from zinc ferrite in this study. Thermodynamic analysis showed that the key to the selective reduction of zinc ferrite to zinc oxide and ferric oxide is to control the appropriate temperature and atmosphere. The influences of the selective reduction roasting process of zinc ferrite on the conversion rate, phase change, and microevolution behavior were investigated. The microstructure analysis showed that the distribution area of iron was mainly gray, and the distribution area of zinc was mainly white grid lines. The zinc content in the white area was higher than that in the gray area. With the increase in temperature and PCO, the white area expanded and the migration of zinc and iron was accelerated, but the iron in the white area still existed. The ammonia leaching of the magnetization-roasted product showed that a zinc leaching rate of 78.12% was achieved under the following conditions: the roasting atmosphere of PCO/P(CO+CO2) = 25%, the roasting temperature of 750 °C, roasting duration for 45 min, n(NH3-H2O):n(NH4Cl) = 1:1, the solid–liquid ratio of 40 g/L, leachate concentration of 6 mol/L, leaching duration of 90 min, the leaching temperature of 50 °C, and the stirring rate of 200 rpm.