| There are abundant reserves of manganese ore in China, manganese ore c urrently is mainly used for the preparation of electrolytic manganese. It is an important issue to prepare higher value-added products from manganese ore. With Pyrolusite in Xiangxi(Hunan) as raw material, soft magnetic ferrite was prepared. This investigation was composed of the following parts:With pyrolusite as raw material and iron as reductant, the leaching solutio-n was obtained by sulfuric acid leaching. It was deoxidized and purified, so it became mixed solution of Fe2+ and Mn2+. FeSO4·7H2O and ZnSO4·7H2O were added into the mixed solution in proportion. Eventually, MnZn ferrite precur-sor was obtained by co-precipitation, with NH4HCO3 and NH3·H2O as a preci-pitating agent and zinc stearate as a surfactant.By single factor way, result showed that the optimum leaching conditions were as below:ratio of Fe and Mn was 0.8:1, molar ratio of sulfuric acid and manganese was 2.5:1, mass ratio of liquid and solid was 5:1, reaction time was 2h, reaction temperature is at room temperature (15℃), under these condi-tions, the manganese leaching rate was 98.40%.In addition, the optimum conditions of removing calcium and magnesium by NH4F are as below:NH4F was 3 times more than Ca2+ and Mg2+, pH va-lue was 3.5, the reaction temperature was 90℃, the precipitation time was 1.5h, under these conditions, the highest removal rates of Ca2+ and Mg2+ were 94.8% and 85.2%, respectively. Besides, the optimum conditions for co-precipi-tation were:ammonication coefficient was 1.8, pH value was 7.5, reaction temperature was 40℃, reaction time was 60min, standing time was 12h. Mn-Zn ferrite particles prepared by coprecipitation were uniform spherical particles, whose diameter was about lμm, and saturation magnetic induction was 60.45e mu/g.Mn-Zn ferrite powders obtained by 2 ways:one was by direct leaching from soft manganese ore, another was by H2SO4, result showed that the satura-tion magnetic flux density were about the same.The manganese sulfate solution was obtained by sulfuric acid leaching, wit h pyrolusite as raw material and orange peel as a reducing agent. Later it was purified. Mn3O4 was prepared by direct oxidation of free Mn2+, with air and MnO2 as oxidizing agent, respectively. MnZn ferrite was prepared by high-ene rgy ball milling method, with the Mn3O4, analysis of Fe2O3 and ZnO as raw material.By single factor experiment, the optimum conditions of the orange peel leaching pyrolusite was obtained:mass ratio orange peel and ore was 0.15:1, the reaction temperature was 80℃, sulfuric acid concentration was 3mol/L, li-quid to solid ratio was 6:1, reaction time was 10h. Under this conditions, manganese leaching rate was 98.32%. In one hand, the Mn3O4 was prepared by free Mn2+ that was directly oxidized by air, which was low impurity contai-ning, small particles uniformly and in line with the standards of MnZn ferrite.In the other hand, with MnO2 as oxidizing agent, the Mn3O4 that was pr epa-red by direct oxidation of free Mn2+, which content low manganese and ca n not be used for the synthesis of MnZn ferrite. Because the Mn2+ was direc t hydrolysis precipitation and a part of MnO2 didn’t react. With the Mn3O4 as ore material, which was prepared by air oxidation, MnZn ferrite was obtained by method of high energy ball milling, and the XRD pattern of MnZn ferrite powder shows a pure phase, but its particles showed uneven thickness. Hystere-sis loop analysis chart shows that the soft magnetic was not good, and the M n-Zn ferrite obtained by saturation magnetic flux density and co-precipitation method was little. |
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