Manganese dioxide preparation method

Manganese dioxide is an inorganic compound with a chemical formula of MnO2. It is a black amorphous powder or black orthorhombic crystal. It is hardly soluble in water, weak acid, weak alkali, nitric acid, cold sulfuric acid, and soluble in concentrated hydrochloric acid under heating to produce chlorine gas. . Used in the preparation of manganese salt, and also used as an oxidant, rust remover, and catalyst.

Manganese dioxide preparation method

Mainly from the natural mineral pyrolusite. 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 stripping, 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.

Manganese sulfate

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 to 3 V, usually after 20 to 30 days of electrolysis, a massive crude product is deposited on the anode. The crude product is stripped, crushed, Rinse with water several times, add sodium bicarbonate to neutralize it to pH=5~7, then filter, dry and crush to prepare electrolytic manganese dioxide product.

The manganese chloride method reacts the rhodochrosite with excess hydrochloric acid to produce a manganese chloride solution. After the reaction is completed, lime is added for neutralization, and the pH is controlled to about 4, and the oxidant hydrogen peroxide is added 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.

Most of them are underground mining, and the general process is the same as "phosphorite". Commonly used beneficiation methods include manual separation, magnetic separation, flotation, gravity separation, etc. In addition, chemical beneficiation and bacterial leaching methods are used in a large number of tests for manganese ore.

Beneficiation process:

In the manganese nitrate method, pyrolusite is mixed with coal powder, high-valence manganese is reduced to manganese monoxide by reduction roasting, leached with nitric acid and sulfuric acid, filtered and purified to obtain manganese nitrate solution, and then concentrated and thermally decomposed to obtain manganese dioxide. Finally, after dilute nitric acid refining, sulfuric acid activation treatment, water washing, and drying, the manganese dioxide product is obtained.

The manganese carbonate method pyrolusite is finely pulverized and mixed with coal powder, reduced and roasted to generate manganese oxide, which is leached with sulfuric acid. The resulting manganese sulfate solution is neutralized to pH 4-6, precipitated impurities are filtered to remove residue, and the filtrate is purified by adding sodium sulfide. Press filter, add ammonium bicarbonate and seed crystals to generate manganese carbonate precipitation, pass water vapor in the air to roast at about 450 ℃ and thermally decompose to generate manganese dioxide. The remaining manganese carbonate and low-order manganese oxide are dissolved by sulfuric acid, Sodium is reconstituted, washed and dried to obtain manganese dioxide.

Natural manganese ore activation method

Heat high-quality pyrolusite in the air to 600-800°C, or in the presence of reducing agents (such as pulverized coal, natural gas), heat to 300°C for reduction roasting to reduce manganese dioxide to manganese trioxide. The product is treated with hot sulfuric acid to disproportionate manganese trioxide to obtain high activity. γ-MnO2 and manganese sulfate, the slurry after acid leaching is filtered, washed and dried to obtain active manganese dioxide.

Overview of manganese dioxide MnO2

Manganese dioxide MnO2 is black amorphous powder or black rhombus crystals. Solubility: hardly soluble in water, weak acid, weak base, nitric acid, cold sulfuric acid, insoluble in concentrated hydrochloric acid when heated, generating chlorine gas.

Chemical properties: Manganese dioxide is an amphoteric oxide, with corresponding salts in the form of perovskite structure, such as BaMnO3 or SrMnO3 (obtained by a compound reaction in a molten alkali system). There is also manganese tetrachloride.

In case of reducing agent, it shows oxidizing property. Manganese dioxide is heated to 1400K in a stream of hydrogen to obtain manganese oxide; manganese dioxide is heated in a stream of ammonia to obtain brown-black manganese trioxide. Manganese dioxide reacts with concentrated hydrochloric acid to produce chloride, manganese chloride, chlorine and water.

It also exhibits reducibility in case of strong oxidizing agents, and it is a strong oxidizing agent in acidic media.

Manganese dioxide composition:

Manganese Oxide Water Iron Copper Lead Your Company Mercury Acid Insoluble Sulfate

92.33% 2.17eppm 0.5ppm 0.5ppm 2.0ppm 2.0ppm 47ppm 0.01% 1.2%

Application of manganese dioxide MnO2

Manganese dioxide MnO2 is mainly used as a depolarizer for dry batteries, as a catalyst and oxidant in the synthesis industry, and as a colorant, decolorant and iron removal agent in the glass industry and enamel industry. Used in the manufacture of metal manganese, special alloys, manganese iron castings, gas masks and electronic material ferrites. In addition, it can also be used in the rubber industry to increase the viscosity of rubber. It can also be used as a catalyst in chemical experiments.

Organic synthesis purposes: Manganese dioxide is very useful in organic chemistry. The manganese dioxide used in the oxide has different forms. Since manganese dioxide has many crystal forms, the chemical formula can be written as MnO2-x(H2O)n, where x is between 0 and 0.5, and n can be greater than zero. Potassium permanganate (KMnO₄) and manganese sulfate (MnSO₄) react at different pH values to produce manganese dioxide. The brown manganese dioxide precipitate is very dry and very lively. The most effective organic solvents include aromatics, carbon tetrachloride, ether, tetrahydrofuran and esters.

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 will not be oxidized by manganese dioxide: cis-RCH=CHCH2OH + MnO2 → cis-RCH=CHCHO + H2O + manganese oxide

The product inside will not be oxidized no matter how active it is. Manganese dioxide can oxidize diols to dialdehydes. Other manganese dioxides have many reactions and can be used to oxidize amines, aromatics, and triols.

Laboratory use

Used as a catalyst for the decomposition of hydrogen peroxide (hydrogen peroxide) to produce oxygen. Used as a catalyst when heating potassium chlorate to decompose to produce oxygen. The thermite reaction with elemental aluminum powder produces manganese. Used as pigments, yellow glass, etc. It reacts with hot concentrated hydrochloric acid to generate chlorine gas, and reacts with molten caustic potassium (potassium hydroxide) in the air to prepare potassium manganate.

In the decomposition reaction of potassium permanganate, manganese dioxide acts as a self-catalyst of potassium permanganate.

Manganese dioxide MnO2 price

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Suppliers of Manganese Dioxide MnO2

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