Research status and development of extraction process of zinc-bearing dust from ironmaking and steelmaking—a critical review

Almost 29.57–38.46 million tons of zinc-bearing dust were produced in Chinese iron and steel enterprises annually. The recovery of Zn and other metals in zinc-bearing dust from ironmaking and steelmaking could improve economic efficiency. However, zinc-bearing dust was classified as hazardous waste, and the volatile metals (like Zn, Na, Pb, etc.) in zinc-bearing dust limited the direct reusing in a blast furnace. Therefore, the formation process, fundamental characteristics, and current extraction process of Zn from zinc-bearing dust, associated with thermodynamics and kinetics of the pyrometallurgical process, hydrometallurgical process, and pyro-hydrometallurgical process, were analyzed. It is indicated that industrialized pyrometallurgical processes are undergoing high energy consumption and pollution such as rotary kiln and rotary hearth furnace process. The vacuum carbothermal reduction process can realize low carbon emission and no waste produced in the process. The hydrometallurgical leaching processes in strong acid, strong alkali, and ammonium solutions result in serious liquid pollution and equipment corrosion. The pyrometallurgical process involves complex kinetics and lacks kinetic research on semi-industrialization and industrialization. Water-soluble components in zinc-bearing dust can be removed by water leaching. The kinetics of the strong acid leaching is mainly controlled by the leaching kinetics of Fe₂O₃ and ZnFe₂O₄, while the alkali leaching and weak acid leaching are controlled by the kinetics of ZnO leaching. Zn in the zinc-bearing dust can be extracted by a low-temperature sodium roasting–weak acid leaching process that reduces equipment corrosion and environmental pollution.