Preparation Process Optimization Of Mn-Zn Ferrite From Low-grade Manganese Ore

Mn-Zn ferrite is a kind of essential electronic ceramic, and widely used in the electronics industry. The tons of Low-grade manganese ore (LMO) have become a serious environmental problem, and the comprehensive utilization of LMO has great benefit to both environment and economy. LMO was applied to preparing Mn-Zn ferrite by co-precipitation method after being leached in sulfuric acid medium in this paper. The effects of granule diameter, leaching time, liquid/solid ratio (V/W) and concentration of sulfuric acid were investigated through orthogonal and single factor experiments. X-ray powder diffraction (XRD), Fourier Transform Infrared Spectrometer (FTIR), Brunauer-Emmett-Teller (BET) specific surface area and Scanning Electron Microscope (SEM) were respectively applied to characterize characterizing the crystalline phases and the microstructures of samples, which were synthesized with different ratio of metal salts, pH and SiO₂-doping. The magnetic measurements were carried out on Vibrating Sample Magnetometer (VSM). The main conclusions could be obtained as follows.The optimal manganese extraction conditions of LMO were 0.054 mm of size, 120 min of reaction time, 3 (V/W) of liquid/solid ratio and 30% of concentration of sulfuric acid (g/g). Under these conditions, the leaching efficiency could reach up to 96.7%. The kinetics of the leaching process was in accordance with characteristics of fractal reaction, the fractal-like kinetics parameters h and k 0being 1.65 and 5.51 min-1 respectively. The maintaining effect of manganese was rather significant with a recovery of 97.1%, whtle while the iron presented a recovery of 62.5% in the purification process.The saturation magnetization of Mn-Zn ferrite simultaneously increased with the increase of the ratio of zinc as it was less than 22.32%, and decreased on further increase in Zn concentration. Besides, its coercivity decreased with the increase of pH as it was below 7.5, but increased when it got over 7.5. As a result, the optimal sample could be obtained with a saturation magnetization of 55.02 emu/g, a coercivity of 8.20 G and a residual magnetization of 1.71 emu/g when the ratio of zinc was 22.32% and pH was 7.5.The results showed that synthesis ratio of precursor was strongly influenced by the co-precipitation temperature, could reached up to 87.9% (maximum value) at the temperature of 50℃. SiO₂ doping enhanced the specific area of Mn-Zn ferrite with a proper amount. A certain amount of SiO₂ doping (0-0.45 wt %) could improve the magnetic property of Mn-Zn ferrite, while excessive doping decreased the magnetic property due to change of its phase structure. When SiO₂ doping was 0.45%, the optimal sample was obtained, which have had a saturation magnetization of 71.95 emu/g, a coercivity of 10.49 G and a residual magnetization of 1.32emu/g.