It is generally prepared by high-temperature manganese sulfate solution electrolysis, and both manganese carbonate and pyrolusite can be used as raw materials. The preparation of manganese sulfate solution includes leaching, iron removal, neutralization, heavy metal removal, filtration, static removal of calcium and magnesium, etc. The crude product is obtained after high-temperature electrolysis and then processed including peeling, crushing, washing, neutralization and Qualified crystals were obtained through drying and other processes. When manganese chloride solution is used for electrolysis, fibrous manganese dioxide can be produced. There are also manganese carbonate and manganese nitrate pyrolysis methods, which are prepared by direct oxidation by combining low-valent manganese oxide with oxidants such as sodium chlorate, chlorine, oxygen, etc., respectively.
Mix rhodochrosite powder and sulfuric acid according to the mass ratio of 1:1.8～1:2.0 to produce manganese sulfate. Under normal circumstances, use the circulating acid of the electrolytic cell and supplement part of the sulfuric acid. When the pH=4, add a small amount of manganese dioxide Powder, oxidize Fe2+ in the solution to Fe3+, then add lime milk to neutralize the pH to near neutral, add a saturated solution of barium sulfide to precipitate heavy metal ions to form sulfides, and filter to prepare electrolyte composition: MnSO4=120±20 g/L, H2SO4=30±10 g/L, at a temperature of 93±5°C and a cell voltage of 2～3 V, usually after 20～30 days of electrolysis, a massive crude product is deposited on the anode, and the crude product is stripped and crushed, Rinse with water several times, and add sodium bicarbonate to neutralize to pH=5~7, then filter, dry and crush to prepare electrolytic manganese dioxide product.
The chemical equations:
The manganese chloride method reacts with the rhodochrosite with excess hydrochloric acid to produce a manganese chloride solution. After the reaction is completed, add lime to neutralize, control Ph=4, and add oxidant hydrogen peroxide to oxidize Fe2+ to precipitate iron hydroxide. After removal, the purified manganese chloride solution is added with manganese nitrate to prepare the electrolyte, so that the concentration of manganese chloride is 0.5-2.0 mol/L and the concentration of HCl is 0.01-1.0 mol/L. The electrolyte can be added with 10%-15% manganese nitrate and electrolyzed at a temperature of 85-95℃, which can solve the air pollution and corrosion problems caused by the micro-chlorine release reaction during the electrolysis process. The fibrous manganese dioxide is obtained by electrolysis, and then the crude product is stripped, crushed, neutralized and rinsed, filtered, dried, and crushed to obtain an electrolytic manganese dioxide product.
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