Molecular Formula | MnO2 |
Molar Mass | 86.94 |
Density | 5.02 |
Melting Point | 535 °C (dec.) (lit.) |
Water Solubility | insoluble |
Vapor Presure | 0-0Pa at 25℃ |
Appearance | Black powder |
Specific Gravity | 5.026 |
Color | gray |
Exposure Limit | ACGIH: TWA 0.02 mg/m3; TWA 0.1 mg/m3OSHA: Ceiling 5 mg/m3NIOSH: IDLH 500 mg/m3; TWA 1 mg/m3; STEL 3 mg/m3 |
Merck | 14,5730 |
Storage Condition | Store below +30°C. |
Stability | Stable. Incompatible with strong acids, strong reducing agents, organic materials. |
MDL | MFCD00003463 |
Physical and Chemical Properties | Black orthorhombic crystal or brown-black powder. relative density 5.026 solubility insoluble in water and nitric acid, soluble in acetone. |
Use | Used as an oxidant, also used in steel, glass, ceramics, enamel, dry batteries, matches, medicine, etc |
Hazard Symbols | Xn - Harmful |
Risk Codes | 20/22 - Harmful by inhalation and if swallowed. |
Safety Description | 25 - Avoid contact with eyes. |
UN IDs | 3137 |
WGK Germany | 1 |
RTECS | OP0350000 |
TSCA | Yes |
HS Code | 2820 10 00 |
Packing Group | III |
Toxicity | LD50 orally in rats: >40 mmole/kg (Holbrook) |
Raw Materials | Sulfuric acid Sodium Chlorate Manganese(II) carbonate |
Downstream Products | manganese(ii) sulfate Sodium permanganate Potassium permanganate Manganese manganese(ii) sulfate Rifapentine |
Reference Show more | 1. [IF=4.258] Shengjun Bu et al."Point-of-care assay to detect foodborne pathogenic bacteria using a low-cost disposable medical infusion extension line as readout and MnO2 nanoflowers."Food Control. 2019 Apr;98:399 |
black or brown squares of crystalline, amorphous powder or cake. Melting point 535 C (decomposition);d 5.026. Soluble in hydrochloric acid and release chlorine, do not dissolve in water, acetone, nitric acid or concentrated sulfuric acid, but hydrogen peroxide or oxalic acid, can be dissolved in dilute sulfuric acid or nitric acid. With strong oxidation. When heated to about 200 ° C. In hydrogen, manganese dioxide and manganese tetroxide are formed. It is easy to fire and burn in contact with combustible materials and organic matter. Explosive reaction with hydrogen peroxide. Exposure to hydrogen sulfide can cause ignition. A strong reaction can occur with the reducing agent.
The manganese nitrate solution was concentrated by heating and thermally decomposed to obtain manganese dioxide, which was purified by dilute nitric acid, activated by sulfuric acid, washed with water, and dried at 150 ° C. To obtain pure manganese dioxide.
reagents for spectral analysis. For the preparation of manganese salt, oxidant, rust remover, Catalyst, desiccant and determination of sodium sulfide in cement.
rat oral LDso:>40mmol/kg. Manganese oxide dust can cause manganese pneumoconiosis in humans. Staff should be protected. The working environment should be well ventilated. Store in a cool, dry, well-ventilated warehouse. Keep away from fire and heat source. Packaging is required to be sealed and not to be in contact with air. Moisture-proof, sunscreen. Should be stored separately from reducing agents, flammable materials, combustible materials, oxidizing agents, etc.
NIST chemical information | Information provided by: webbook.nist.gov (external link) |
EPA chemical information | Information provided by: ofmpub.epa.gov (external link) |
manganese oxide | manganese dioxide is also called "manganese peroxide", "black manganese oxide", tetravalent manganese oxide, chemical formula MnO2,fHm(298K)=-520.71kJ/mol, melting point 847 ℃, density 5.026g/cm3, natural products exist in pyrolusite, black orthorhombic crystal or black brown powder, it has a tetrahedral lattice, is an amphoteric manganese oxide, insoluble in water and nitric acid. Manganese sulfate is formed by releasing oxygen in hot concentrated sulfuric acid. Chlorinated in hydrochloric acid to form manganese chloride. It is eutectic with caustic and oxidant to release carbon dioxide to form permanganate. Manganese dioxide is a strong oxidant, which can cause combustion and explosion by rubbing or co-heating with organic matter or other oxidizable substances (such as sulfur, sulfide and phosphide, etc.). This product shows reducibility when interacting with strong oxidants (such as hydrogen peroxide). MnO2 is heated to above 480 ℃ in air to convert into Mn2O3 and above 900 ℃ to Mn3O4. It is widely used in steelmaking, and used to make glass, ceramics, dry batteries, etc. In nature, it exists in the form of pyrolusite and hard manganese ore. It can be extracted from pyrolusite, and can also be prepared by heating to decompose manganese nitrate or electrolytic oxidation of divalent manganese salt. γ-MnO2 is active and can be used as a battery cathode material to eliminate polarization. Manganese dioxide can be used as rust remover, oxidant, dry battery dry electrode agent and paint drier, but also used in manganese salt preparation and glass industry. manganese compounds can cause chronic poisoning. the maximum allowable concentration of manganese compounds (converted into manganese dioxide) dust in the air of production sites is 0.3 mg/m3. |
Structure | Manganese dioxide, like many other dioxides, crystallizes in the form of rutile crystal structure, with three coordinated oxides and octahedral metal centers. Manganese dioxide is a typical non-compound compound with oxygen atom vacancy. |
Active manganese dioxide | γ crystalline manganese dioxide (γ-MnO2) is called active manganese dioxide due to its excellent depolarization activity (ie excellent discharge performance). Its powder diffraction pattern is strongly diffracted. It is mainly used in the battery industry and is a high-quality raw material for the battery industry. After being used in the battery industry, the specific capacity of the zinc-manganese battery has been greatly improved. The reason why it has excellent discharge performance is not only because it contains about 90% MnO2 and a very small amount of impurities, but also because its crystal structure is different from natural manganese dioxide, it is a gamma structure and has high activity. For example, natural pyrolusite (β-MnO2) and electrolytic product (γ-MnO2) containing MnO2 of about 90% are respectively made into batteries and then discharged for test. The discharge capacity of the latter is about twice as high as that of the former. Its production methods are:(1) chemical method, mainly manganese carbonate oxidation roasting method, chlorination-oxidation method, sodium chlorate oxidation method, dilute sulfuric acid hot dip method, nitric acid leaching method, etc.;(2) electrochemical method, It is a method of simultaneous production of electrolysis and chemical action, that is, electrolytic production of active manganese dioxide. It is a process that uses electrolysis and chemical action to work at the same time. |
function and main use | natural manganese dioxide (pyrolusite) is an important source of manganese. It is mainly used for steelmaking and manganese alloy making. About 70 ~ 80% of manganese dioxide produced in the world is used in the battery industry. According to statistics in 1976, about 500,000 tons of pyrolusite was consumed for this use. In dry batteries, carbon is the positive electrode, zinc is the negative electrode, and manganese dioxide is used as a depolarizing agent near the carbon electrode to prevent the release of hydrogen, which may be achieved through the following reactions: MnO2 H + e-= MnO(OH). Another main use of manganese dioxide is as a colorant in the brick industry, which can make the bricks appear red, brown or gray. Manganese dioxide is used as a bleach in the glass manufacturing industry and is known as "the soap of glass makers". Because ordinary glass is often green due to trace iron (II), it is not easy to remove this trace iron. If manganese dioxide is added during glass smelting, the glass becomes colorless and transparent. This is because manganese dioxide oxidizes iron (II) to iron (III), and manganese (IV) is reduced to manganese (III). Iron silicate (Ⅲ) is yellow, manganese silicate (Ⅲ). It is purple, yellow and purple complement each other, and it looks colorless. Manganese dioxide is used in the chemical industry to oxidize aniline to hydroquinone (hydroquinone is extremely important in the production of developers, dyes, and paints). In the electronics industry, manganese dioxide is used to synthesize ceramic ferrite MnFe2O4, scanning transformers and deflection coils for televisions. Single crystals with piezoelectric and ferroelectric properties can be prepared by adding oxides of earth elements to manganese dioxide. 50 ~ 60% mixture of manganese dioxide, copper oxide and cobalt oxide (or silver) catalysts are used in special anti-carbon monoxide gas masks as carbon monoxide absorbers. Manganese dioxide is added to the "dry oil" of paint as a drier, which can accelerate the oxidation of oil (such as linseed oil) in the air and make it dry as soon as possible. Manganese dioxide has strong adsorption and is easy to absorb mercury vapor. When manganese dioxide suspension (pH = 2~5) is used for washing mercury vapor in bipolar foam scrubber, 99% mercury can be captured. The amount of mercury absorbed can reach 20% of the dry basis weight of manganese dioxide in the suspended liquid. After mercury is extracted, manganese dioxide is calcined at 500 ℃ for 2 hours and regenerated. Manganese dioxide is also used as an accelerant for the match industry, glaze for ceramics and enamel. The demand for manganese dioxide is increasing day by day, and the mineral source is insufficient. The manufacturing technology of "synthetic manganese dioxide" is being studied, that is, manganese dioxide is produced by electrolytic manganese sulfate anodic oxidation. |
electrolytic manganese dioxide process | electrolytic manganese dioxide process is divided into three main parts: preparation of manganese sulfate solution, electrolysis and finished product treatment. the process flow is shown in the figure. The preparation of manganese sulfate solution includes leaching, iron removal, neutralization, heavy metal removal, coarse filtration, fine filtration and static precipitation to remove magnesium and calcium. The raw materials used are manganese carbonate ore powder (126 mesh, containing Mn20-23%), industrial sulfuric acid (containing H2SO4>93%) and natural MnO2 powder (for iron removal, content 30-35%). Refined manganese sulfate solution contains MnSO4165g/L-180g/L,Fe edited by Zhang xianpeng. Ferroalloy dictionary. Shenyang: Liaoning Science and Technology Press. 1996. Page 103-104. |
toxicity | see chemical manganese dioxide. Manganese oxide dust can cause human manganese pneumoconiosis. High-valent manganese oxides, regardless of the way they invade the body, have toxic effects on the brain. See metal manganese for others. |
use | is a strong oxidant, mainly used as depolarizing agent for dry batteries, decolorizing agent for glass industry, desiccant for paint ink, gas mask absorbent, match combustion aid, etc. mainly used as depolarizing agent for dry batteries. It is a good decolorant in the glass industry, which can oxidize low-priced iron salts to high-iron salts, turning the blue-green of glass into weak yellow. Used in the electronics industry to make manganese-zinc ferrite magnetic materials. Used as a raw material for iron-manganese alloys in the steelmaking industry and a heating agent for the casting industry. Used as an absorbent for carbon monoxide in gas masks. Used in the chemical industry as an oxidant (such as purple red synthesis), a catalyst for organic synthesis, a desiccant for paints and inks. It is also used as an accelerant for the match industry, as a raw material for ceramics, enamel glaze and manganese salt. It is also used for pyrotechnics, water purification, iron removal, medicine, fertilizer and fabric printing and dyeing. It is used in the chemical industry to produce manganese sulfate, potassium permanganate, manganese carbonate, manganese chloride, manganese nitrate, manganese monoxide, etc. Manganese sulfate is used as a fertilizer and feed additive. The pharmaceutical sector uses manganese compounds as disinfectants, oxidants, catalysts, gastric lavage agents and emetic agents. Manganese is used as a desulfurizer for dry batteries and nitrogen fertilizer production; it is also widely used in metallurgy, ceramics, glass, light industry, machinery, matches, electronics, dyes, national defense, communications, environmental protection and other departments. See Chemical Manganese Dioxide. It is used as a depolarizer for dry batteries, a catalyst and an oxidant for the synthesis industry, a colorant, a disinfectant, and an iron remover for the glass industry and the enamel industry. Used in the manufacture of metallic manganese, special alloys, ferromanganese castings, gas masks and electronic materials such as ferrite. In addition, it can also be used in the rubber industry to increase the viscosity of rubber. Oxidant, special alloy steel, catalyst, desiccant, determination of sodium sulfide in cement. It is widely used in steelmaking and in making glass, ceramics, enamel, dry batteries, etc. Used as an oxidant, also used in steelmaking, glass, ceramics, enamel, dry batteries, matches, medicine, etc. |
production method | manganese sulfate method mixes rhodochrosite powder and sulfuric acid according to the mass ratio l:1.8~1:2.0 to generate manganese sulfate. under normal circumstances, circulating acid of electrolytic cell is used and part of sulfuric acid is added. when Ph4 is added, a small amount of manganese dioxide powder is added to oxidize Fe2 + in the solution to Fe3 +, then add lime milk to neutralize until Ph is nearly neutral, add human barium sulfide saturated solution to generate sulfide precipitation of heavy metal ions, filter to prepare electrolyte composition: MnSO 4120±20g/L, H7SO 430±10g/L, at a temperature of 93±5 ℃ and a tank voltage of 2~3V, usually after 20~30 days of electrolysis, the bulk coarse product is deposited on the anode, the crude product is stripped, crushed, rinsed with water for many times, and added with sodium bicarbonate to neutralize until Ph 5~7, then filtered, dried and crushed to obtain electrolytic manganese dioxide product. Its MnCO3 + H2SO4 → MnSO4 + H2O + C02 ↑ 2FeSO4 + MnO2 +2H2SO4 → Fe2(SO4)3 + MnSO4 +2H2OFe2(SO4)3 + 6H2O → 3H2SO4+2Fe(OH)3 ↓ MnSO4 + 2H2O [electrolysis] → MnO2 + H2SO4 + H2 manganese chloride method reacts with excess hydrochloric acid to generate manganese chloride solution. After the reaction is completed, lime is added for neutralization, control about Ph4, add oxidant hydrogen peroxide to oxidize Fe2 + to generate ferric hydroxide precipitation and remove it, and add manganese nitrate to the purified manganese chloride solution to prepare electrolyte to make manganese chloride concentration 0.5~2.0 mol/L and HCl concentration 0.01~1.0 mol/L. Manganese nitrate with a content of 10% ~ 15% can be added to the electrolyte and electrolyzed at a temperature of 85~95 ℃, which can solve the air pollution and corrosion problems caused by the release reaction of trace chlorine in the electrolysis process. Electrolysis to obtain fibrous manganese dioxide, and then through the crude peeling, crushing, neutralization rinsing, filtration, drying, crushing, electrolytic manganese dioxide products. Its MnCO3 + 2HCl → MnCl2 + H20 + CO2 ↑ Mncl2 + 2H2O [electrolysis] → MnO2 + 2HCl + H2 ↑ is mostly underground mining, and the general process flow is the same as "phosphate block rock". Commonly used beneficiation methods include hand separation, magnetic separation, flotation, gravity separation, etc. In addition, chemical beneficiation and bacterial leaching methods have been used for manganese ore with a large number of tests. The beneficiation process of Xiangtan manganese ore in Hunan Province is as follows: Manganese nitrate method mixes pyrolusite and pulverized coal, reduces high-priced manganese to manganese monoxide through reduction roasting, leached with nitric acid and sulfuric acid, filtered and purified to obtain manganese nitrate solution, then concentrated and thermally decomposed to obtain manganese dioxide, and finally refined by dilute nitric acid, activated by sulfuric acid, washed and dried to obtain chemical manganese dioxide products. Its MnO2 + C → MnO + COMnO2 + CO → MnO + CO2MnO +2HNO3 → Mn(NO3)2 + H2OMn(NO3)2 → MnO2 +2NO2 manganese carbonate pyrolusite is finely crushed and mixed with pulverized coal, reduced roasting is carried out to generate manganese oxide, leached with sulfuric acid, the obtained manganese sulfate solution is neutralized to Ph4 ~ 6, precipitated impurities are filtered to remove slag, the filtrate is purified with sodium sulfide, and the filtrate is pressure filtered, ammonium bicarbonate and seed crystals are added to generate manganese carbonate precipitate, and steam is passed in the air and roasted at about 450 ℃ for thermal decomposition to generate manganese dioxide, the remaining manganese carbonate and low-priced manganese oxide, which are dissolved by sulfuric acid and heavy sodium chlorate Chemical manganese dioxide is obtained by washing and drying. Its 2MnO2 + C → 2MnO + CO2 ↑ MnO + H2SO4 → MnSO4 + H2OMnSO4 +2NH4HCO3 → MnCO3 +2NH4HSO4MnCO3+0.5O2 → MnO2 + CO2 ↑ MnCO3 + H2SO4 → MnSO4 + H2O + CO2 ↑ 5MnSO4+2NaC1O3 + 4H2O → 5MnO2 + Na2SO4 +4H2SO4 + C12 ↑ natural manganese ore activation method heats high quality pyrolusite to 600~800 ℃ in air, or in the presence of reducing agents (such as pulverized coal and natural gas), heating to 300 ℃ for reduction roasting to reduce manganese dioxide to generate manganese trioxide, and the reduction product is then treated with hot sulfuric acid to disproportionate manganese trioxide to obtain high activity. γ-MnO2 and manganese sulfate, after acid leaching, the slurry is filtered, washed, dried, and activated manganese dioxide is prepared. Its 2MnO2 + C → Mn2O3 + COMn2O3 + H2SO4 → MnSO4 + MnO2 + H2O |
category | oxidant |
toxicity classification | poisoning |
acute toxicity | oral-rat LD50: > 3478 mg/kg |
flammability hazard characteristics | non-combustible; toxic manganese smoke from the fire site |
storage and transportation characteristics | warehouse ventilation; light loading and unloading; separate from organic matter, reducing agent, sulfur and phosphorus flammable materials |
fire extinguishing agent | water, carbon dioxide, dry powder, sand |
occupational standard | TWA 5 mg (manganese)/m3 |