Zinc efficiently extracted from zinc calcine by reduced wet grinding: ZnFe2O4 to ZnO and Fe3O4

In traditional zinc metallurgy, the unique spinel structure of zinc ferrite (ZnFe2O4) leads to low zinc leaching efficiency. The reduced wet grinding is adopted to selectively decompose ZnFe2O4 to ZnO, which is easily leached out, and Fe3O4 which is difficult to leach out. The results show that zinc leaching efficiency reached 90.78% under the optimum conditions: mass ratio of H2C2O4·2H2O and ZC 3.60 wt%, ball-to-material ratio 2:1, sulfuric acid concentration 70 g L−1, and liquid-to-solid ratio 10:1 mL g−1, and reduced wet grinding of 60 min and 40 Hz. It is 3, 8, and 10 percentage points higher than that of dry ball milling, reduced leaching (with H2C2O4·2H2O but without mechanical activation), and leaching (without H2C2O4·2H2O and mechanical activation). Reduced wet grinding leads to a reduction in particle size and an increase in the specific surface area of ZC. This further causes a distortion of the ZnFe2O4 lattice, and approximately 42% ZnFe2O4 is reduced to ZnO and Fe3O4. Meanwhile, 92% Zn2SiO4 is also leached. Reduced wet grinding, an enhanced leaching process, results in a higher zinc leaching efficiency and reduces the production of hazardous waste, providing a novel approach for the zinc metallurgic industry in the future.