Study on the preparation of Mn–Zn soft magnetic ferrite powders from waste Zn–Mn dry batteries

Using waste Zn–Mn dry batteries, waste scrap iron and pyrolusite as raw materials, Mn–Zn soft magnetic ferrite powders were prepared through the process of simultaneous leaching, purification and co-precipitation. The experimental results indicated that the leached yields of Fe, Mn and Zn were 92.02%, 96.14% and 98.34%, respectively. The leached liquor was purified through these processes of sulfuration precipitation, fluorination precipitation and double salt precipitation deep purification process. Therefore, high removal yields of impurities could be achieved. Removal yields were as follows: Ca 99.7%, Mg 92.33%, Al 96.48%, Si 63.64%, Cu 99.86%, Pb 98.51%, Cd 53.0% and Ni 78.72%. Among these co-precipitation powders, the average mass content of the main components were Fe 41.41%, Mn 13.92% and Zn 4.49%, and the mass ratio of Fe:Zn:Mn was 69.2:23.3:7.5. Compared with the theoretical prescription (Fe:Mn:Zn = 67.3:24.4:8.3), the absolute errors of main components were Fe +1.9%, Mn −1.1% and Zn −0.8%. Because of content impurities in co-precipitation powders (Ca < 0.0028%, Mg < 0.0053%, Al < 0.0084%, SiO2 < 0.0023%, Pb < 0.0031% and Cu < 0.0010%), the qualities of these gained co-precipitation powders could compete with the demand for the preparation of soft magnetic ferrite. The magnetic properties also demonstrated that the soft magnetic ferrite samples, which were made from the co-precipitation powders prepared by used batteries, had the same qualities as PC30 made by the TDK Company.