What is manganese dioxide?
Manganese dioxide is an inorganic compound with the chemical formula MnO2, a black amorphous powder or black rhombohedral crystal, insoluble in water, weak acids, weak bases, nitric acid, cold sulfuric acid, and dissolved in concentrated hydrochloric acid under heating to produce chlorine gas. It is used in the preparation of manganese salt, and also used as an oxidizer and rust remover.
Preparation of Manganese Dioxide
Manganese dioxide is mainly obtained from the natural mineral soft manganese ore. It is generally produced by electrolysis of high-temperature manganese sulfate solution, and both manganese carbonate ore and soft manganese ore 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. After high-temperature electrolysis, crude products are produced and then qualified crystals are produced after treatment including stripping, crushing, washing, neutralization, and drying, etc. When using manganese chloride solution electrolysis can produce fibrous manganese dioxide. There are also manganese carbonate, manganese nitrate pyrolysis method, which is made by the direct oxidation of low-valent manganese oxide and oxidants such as sodium chlorate, chlorine gas, oxygen, etc. respectively combined reaction.
Application fields of manganese dioxide
Manganese dioxide can be used as a depolarizing agent of the dry cell, catalyst and oxidizing agent of synthetic industry, coloring agent, decolorizing agent and deironing agent of the glass industry and enamel industry, etc. It is used in the manufacture of manganese metal, special alloy, ferromanganese casting, gas mask, and electronic material ferrite, etc. In addition, it can also be used in the rubber industry to increase the stickiness of rubber. It can also be used as catalyst in chemical experiments.
Manganese dioxide organic synthesis use
Manganese dioxide is very useful in organic chemistry. The form of manganese dioxide used in oxides varies, as it has several crystalline forms, and the formula can be written as MnO2-x(H2O)n, where x ranges from 0 to 0.5 and n can be greater than 0. Manganese dioxide can be produced in reactions of potassium permanganate (KMnO₄) and manganese sulfate (MnSO₄) at different pHs. at different pHs.
One of the chemical reactions dedicated to manganese dioxide is the conversion of alcohols to aldehydes. Even if the alcohol has a double bond, it is not oxidized by manganese dioxide:
cis-RCH=CHCH2OH + MnO2 → cis-RCH=CHCHCHO + H2O + MnO
The product will not be oxidized again even if it is more active. Diols can be oxidized by manganese dioxide to dialdehyde. Other reactions of manganese dioxide are extremely numerous and can be used to oxidize amines, aromatic substances, and triols.
Laboratory uses of manganese dioxide
Used as a catalyst in the decomposition of hydrogen peroxide to produce oxygen.
Used as a catalyst for the decomposition of potassium chlorate by heating to produce oxygen.
Aluminothermic reaction with monolithic aluminum powder to produce manganese.
Used as a pigment, yellow glass, etc.
Reacts with hot concentrated hydrochloric acid to make chlorine gas.
Reacts with molten caustic potash (potassium hydroxide) in the air to produce potassium manganate.
In the decomposition reaction of potassium permanganate, manganese dioxide is used as an autocatalyst for potassium permanganate.
Overview of manganese dioxide Toxicity
Health hazards: Excessive amounts of manganese entering the body can cause poisoning. Acute poisoning is rare in industrial production, especially in the extrapyramidal system. If a large amount of fumes of this product is inhaled for a short time, "metal fume fever" can occur, and the patient will have headaches, nausea, chills, high fever, and sweating. Chronic poisoning includes neurasthenia syndrome, disorders of plant nerve function, mental symptoms of imbalance between excitation and inhibition, and toxic psychosis in severe cases; extrapyramidal damage includes increased muscle tone, tremor, speech disorders, gait abnormalities, etc.
Flammability hazard: The product is non-flammable and irritating.
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