China Nonferrous Metallurgy

Steelmaking dust is one of the solid wastes produced in metallurgical industry, and it has a higher Zn content. The separation and recovery of Zn from steelmaking dust is of great significance to green and low-carbon development of metallurgical industry. Zn mainly exists in the form of ZnFe₂O₄ in steelmaking dust. In order to separate Zn and Fe, CaO modification was adopted to convert ZnFe₂O₄ into ZnO, and then selective leaching was used to extract the Zn element by using dilute hydrochloric acid. The effects of CaO modification, pH value, temperature, and solid-liquid ratio on the dissolution of Zn and other elements from steelmaking dust were investigated. CaO modification could effectively convert the ZnFe₂O₄ into Ca₂Fe₂O₅ and ZnO, which is easily soluble in acidic solution, resulting in a higher dissolution ratio of Zn and making Fe difficult to dissolve; as the pH decreased, the leaching ratios of the main elements from the modified dust increased; increasing the temperature and reducing the solid-liquid ratio are beneficial for the leaching of Zn, and increasing temperature will inhibit the leaching of Si. Under the conditions of pH=3, temperature 50℃, solid-liquid ratio 1∶25, the leaching ratio of Zn was 72.73%, while that of Fe was not leached, achieving selective leaching of Zn. After leaching, electrolytic deposition can be used to recover metal Zn from the leachate. The leaching residue is mainly composed of Ca₂Fe₂O₅, and can be reused as a metallurgical flux.