Synthesis of manganese–zinc ferrite by powder mixing using ferric oxide from a steel mill acid recovery unit

With the aim of producing fine-grained manganese–zinc (Mn–Zn) ferrite at the end of a calcination process at moderate temperatures, this study consisted, at first, of an “electrochemically designed” powder mixing by wet-ball milling a mixture of manganese (MnO2), zinc (ZnO), and iron (Fe2O3 granules produced by an acid recovery unit of a Brazilian steelmaker, milled to fine sizes using alkaline media) –based raw materials. This mixing/milling resulted in improved size reduction when compared to milling without any alkali addition. Further, noticeable size reduction was achieved when elemental Zn was used in place of ZnO, especially when ammonia was used as the medium. Calcination of the alkaline-milled mixture of MnO2 + ZnO + Fe2O3 at 1200 °C allowed obtaining well-crystallized single-phase Mn–Zn ferrite, whereas calcination of the MnO2 + ZnO + Fe2O3 mill-mixed in 100% NH4OH at 1200 °C produced the highest saturation magnetization in the as-calcined state.