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Various preparation methods of manganese dioxide

wallpapers Tech 2021-04-02
Overview of manganese dioxide
Manganese dioxide (IV valence) is an inorganic compound with the chemical formula MnO2. This black or brown solid exists in nature in the form of pyrolusite (mainly manganese-containing ore) and is also a component of manganese nodules. Manganese dioxide is mainly used in dry batteries, such as alkaline batteries and carbon-zinc batteries. Manganese dioxide can also be used as a precursor for pigments or other manganese compounds (such as potassium permanganate). Manganese dioxide can be used as an organic synthesis reagent, for example for the oxidation of allyl alcohol. Manganese dioxide in the alpha polycrystalline phase can combine various atoms (and water molecules) in the "tunnels" or "channels" between the manganese oxide octahedrons. There is great interest in the possibility of α-manganese dioxide as the cathode of lithium-ion batteries.
 
Chemical preparation of manganese dioxide
The first method is to use natural manganese dioxide as raw material, using dinitrogen tetroxide and water to convert it into a manganese nitrate (II valence) solution. The water evaporates, leaving behind crystalline nitrates. At a temperature of 400°C, the salt decomposes, releasing dinitrogen tetroxide and leaving a residue of purified manganese dioxide. These two steps can be summarized as MnO2 + N2O4 ⇌ Mn(NO3)2
 
In the second method, manganese dioxide is carbothermal reduced to manganese monoxide (II valence), and dissolved in sulfuric acid. The filtered solution was precipitated with ammonium carbonate to obtain manganese carbonate. The manganese carbonate is calcined in air to obtain a mixture of II-valent manganese and IV-valent manganese oxide. To complete this process, a sulfuric acid suspension of this material is treated with sodium chlorate. The chloric acid formed in situ converts all III-valent manganese and II-valent manganese oxides into manganese dioxide while releasing chlorine as a by-product.
 
The third preparation process involves manganese epoxide and manganese monoxide. Combine these two reagents in a ratio of 1:3 to form manganese dioxide: Mn2O7 + 3 MnO → 5 MnO2
The last method is to use the chemical reaction of potassium permanganate and manganese sulfate crystals to produce manganese dioxide: 2 KMnO4 + 3 MnSO4 + 2 H2O→ 5 MnO2 + K2SO4 + 2 H2SO4
 

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