Study On New Reduction Technology For Low-grade Complex Manganese Dioxide Ores

The reserve of low-grade manganese dioxide ores is rich in our country. Manganese industry urgently use the manganese dioxide ore to product electrolytic manganese currently, expend the source of production raw material, safeguard the resources security. So it is the key technology and difficulty to develop the new reduction technology for manganese dioxide ores. The reductive leaching process was studied respectively by selection of sodium sulfite, hydrogen peroxide and corncob. The main contents are as follows:(1) Extraction of manganese from low-grade complex manganese dioxide ores was investigated using strong reduction of sodium sulfite in sulfuric acid medium. The leaching efficiency of manganese reached 91.9%. The optimal condition which was determined as sodium sulfite amount of 5g, sulfuric acid concentration of 2 mol/L, average ore size of 100μm, liquid to solid ratio of 5, leaching temperature of 80℃for 45 min. The advantages of this method are high leaching rate, high leaching efficiency and low cost, to provide an economical and effective way for the comprehensive utilization of low-grade manganese dioxide ore.(2) Extraction of manganese from low-grade complex manganese dioxide ores was studied using hydrogen peroxide at the room temperature. The leaching efficiency of manganese reached 92.35%. The optimal condition which was determined as hydrogen peroxide amount of 5g, the amount of sulfuric acid of 2 mol/L, average ore size of 100μm, leaching time of 45 min, liquid to solid ratio of 5. The advantages of the method are low temperature, fast and efficient and no pollution.(3) Manganese dioxide was reduced by corncob in acid medium, and the reaction products were divalent manganese, carbon dioxide and water. The leaching efficiency of manganese reached 92.8% whilst iron dissolved was 24.6% under the optimal condition which was determined as corncob amount of 3g, average ore size of 75μm, sulfuric acid concentration of 1.9 mol/L, leaching temperature of 85℃for 60 min while keeping liquid to solid ratio of 10. The advantages of the corncob are cheap, extensive sources, high leaching efficiency and so on. This new technology is the resource utilization of the crop waste, and it is in accord with the circular economic development model.(4) In addition, we discussed the thermodynamics and kinetics of the manganese leahcing using corncob as reductant. The possibility of manganese leaching with corncob as reductant was investigated through themodynamic calculation. As a result, the Gibbs free energy and equilibrious constant were calculated, and the leaching reaction was proved to be complete. In the study, the effects of stirring rate, leaching temperature, average ore size, sulfuric acid concentration and the amount of reducing agent on the leaching rate of manganese were discussed. The overall kinetical equation was obtained. The leaching process was controlled by the diffusion through the solid film. A shrinking core model was used to describe the leahcing kinetics. The apparent action energy was calculated to be-12.96kJ·mol-1, the apparent reaction order of sulfuric acid concentration was 1.0856, and that of the amount of the corncob was 0.7293. The equation accorded with the kinetics characters was:...