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How is Manganese Dioxide produced?

wallpapers News 2021-11-09
Naturally occurring manganese dioxide contains impurities and a large amount of manganese trioxide. Only a limited number of deposits contain gamma modifiers of sufficient purity to meet the needs of the battery industry.
The production of batteries and ferrites (the two main uses of manganese dioxide) requires high-purity manganese dioxide. The battery needs "electrolytic manganese dioxide", and the ferrite needs "chemical manganese dioxide".
1. Chemical Manganese Dioxide
One method is to start with natural manganese dioxide and then use dinitrogen tetroxide and water to convert it into a solution of manganese (II) nitrate. The evaporation of water leaves crystallized nitrates. At a temperature of 400°C, the salt decomposes, releasing N2O4 and leaving a pure manganese dioxide residue. These two steps can be summarized as:
MnO2 +N2O4⇌Mn(NO3)2
2. Carbothermal reduction of manganese dioxide
In another method, manganese dioxide is carbothermal reduced to manganese (II) oxide dissolved in sulfuric acid. The filtered solution was treated with ammonium carbonate to precipitate MnCO.
The carbonate is calcined in air to obtain a mixture of manganese (II) and manganese (IV) oxides. To complete the process, the suspension of the material in sulfuric acid is treated with sodium chlorate. The chloric acid formed in situ can convert any Mn(III) and Mn(II) oxides into carbon dioxide, releasing chlorine by-products.
3. Manganese epoxide and manganese monoxide
The third method involves manganese epoxide and manganese monoxide. The two reagents are mixed in a ratio of 1:3 to form manganese dioxide:
Mn2O7 + 3 MnO→5 MnO2
Finally, the effect of potassium permanganate on manganese sulfate crystals produces the desired oxide.
2 KMnO4 + 3 MnSO4 + 2 H2O→5 MnO2 + K2SO4 + 2 H2SO4
4. Electrolytic Manganese Dioxide
Electrolytic manganese dioxide (EMD) is used in zinc-carbon batteries together with zinc chloride and ammonium chloride. EMD has also commonly used in manganese zinc dioxide rechargeable alkaline (Zn RAM) batteries. For these applications, purity is critical. The production method of EMD is similar to the production method of electrolytic ductile pitch (ETP) copper: manganese dioxide is dissolved in sulfuric acid (sometimes mixed with manganese sulfate) and electricity is applied between the two electrodes. The dissolved MnO2 enters the solution in the form of sulfate and is deposited on the anode.

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