A New Technique On Deoxidize Pyrolusite And Preparing Manganese Sulfate

Pyrolusite is an important raw material of preparing manganese sulfate, and about 60% manganese sulfate was produced by pyrolusite. Coal was used as reducer in traditional technology in order to convert manganese dioxide to manganese oxide, then leaching by sulfuric acid. But there are many disadvantages such as consuming too much energy, bad operation condition and polluting environment. A newly Co-calcining technology has disadvantages too. Such as Co-calcining pyrolusite and pyrite technology, which MnO2 translated into MnSO4, FeS2 translated into Fe2O3, then leached by water, not only need calcining long time under high proportion of sulfur and manganese but also pyrite can't be used sufficiently, Additionally residue and exhaust gas were discarded. In leached pyrolusite directly by acid technology, Mn extraction was low usually, additionally other factors such as residue were discarded and need amount of H2SO4 were occurred also. So it is necessary to develop a new technique to replace traditional technology, which can decrease pollution, increase the utilization ratio of resources. In this issues, a recyclable reducer, which has wide resource, don't contain poisonous elements, was used as reducer to replace traditional reducer coal. Under appropriate condition pyrolusite will react with reducer directly, and manganese dioxide converted to manganese oxide, then leached by sulphuric acid, and manganese sulphate was gained.The paper aimed at improving the leaching rate of manganese, found out the character of kinetics, thermodynamics of deoxidize and leaching process according to thermo gravimetric analysis, the model of shrinking core and experimental data. At last concluded the best technique condition in theory. The mechanism of deoxidizing pyrolusite was investigated by exploring the ratio of reducer and pyrolusite, the thickness of stack and particle size. The leaching process was a liquid-solid system reaction. According to the theory of shrinking core model, the reaction rate was controlled by the solid film diffuse step. Decreasing the particle size and increasing the leaching temperature will benefit to the reaction rate. The results showed that the leaching rate of Manganese will reach 93.23% when the ratio of reducer and pyrolusite was 0.4, lixivium's pH was about 2.0 at 95℃ and the time was 90 min. When Leachate was purified, MnSO4·H2O was gained by crystallized which can meet with National Standard(GB1622-86). In addition to the material can be gained easily, the process didn't need additional energy, investment cost was low, without pollution, the product MnSO4·H2O had good quality and the technology was suited to low-grade pyrolusite too.