1313-13-9

Description

Manganese dioxide is a black or brown solid widely utilized for various applications. It serves as a catalyst and is predominantly employed as a depolarizer in dry cell batteries, making it a crucial non-metallic form of manganese. In traditional alkaline and rechargeable battery cells, manganese dioxide undergoes a redox reaction, becoming Manganese III oxide. Its versatility extends to applications in lithium-ion technologies.

Chemical Properties

Manganese dioxide ( MnO2 ) , known as pyrolusite when found in nature , is the most plentiful of all the manganese compounds. MnO2 is Iron-black to dark steel-gray or bluish mineral; black or bluish-black streak; metallic or dull luster. Soluble in hydrochloric acid. Manganese dioxide is an important component in batteries. It is also used in glassmaking to remove the green fint caused by iron impurities.

Toxicity evaluation

Inhalation exposure to high concentrations of manganese dusts (specifically manganese dioxide [MnO2] and manganese tetroxide [Mn3O4]) can cause an inflammatory response in the lung, which, over time, can result in impaired lung function. Lung toxicity is manifested as an increased susceptibility to infections such as bronchitis and can result in manganic pneumonia. Pneumonia has also been observed following acute inhalation exposures to particulates containing other metals. Thus, this effect might be characteristic of inhalable particulate matter and might not depend solely on the manganese content of the particle.

Physical properties

Black tetragonal crystals; density 5.08 g/cm3; Moh’s hardness 6.3; decomposes at 535°C; insoluble in water.

Uses

Acts as a colorant and decolorizer in the production of brick, tile, porcelain, and glass. It serves as a drier for paints and varnishes, a preparation for printing and dyeing textiles, and a curing agent for polysulfide rubbers.

Primarily used as a depolarizer in dry cell batteries, both alkaline and rechargeable, participating in redox reactions crucial for battery function. It is also utilized in lithium-ion technologies.

Preparation

Pure manganese(IV) oxide (precipitate form) may be prepared by reducing permanganate ion with a manganous salt: 2KMnO4 + 3MnSO4 + 2H2O → 5MnO2 + K2SO4 + 2H2SO4 Manganese(IV) oxide can also be precipitated by oxidation of a manganese(II) salt using an oxidizing agent such as hypochlorite or peroxydisulphate: Mn2+ + S2O82– + 2H2O → MnO2 + 2SO42– + 4H+ Manganese(IV) oxide may also be made by thermal decomposition of manganese(II) nitrate; or from roasting manganese(II) carbonate in air: Mn(NO3)2 → MnO2 + 2NO2 MnCO3 + ? O2 → MnO2 + CO2 A highly active gamma-MnO2 can be produced by treating manganese(III) oxide with hot sulfuric acid: Mn2O3 + H2SO4 → MnO2 + MnSO4 + H2O Mn2O3 is derived from pyrolusite by heating the mineral at 600–800°C or reducing with powdered coal at 300°C.

Reactivity Profile

The stability of manganese dioxide is due primarily to its insolubility. It is, however, readily attacked by reducing agents in acid solution, for example oxidizing concentrated hydrochloric acid to chlorine. In hot concentrated alkali it dissolves to give a purple solution which contains an equimolar mixture of trivalent manganese, probably as (Mn(OH)6)3- and manganate(V), (MnO4)3-. Manganese dioxide is also one of the most active catalysts for the oxidation of carbon monoxide near room temperature.

Hazard

Oxidizing agent, may ignite organic materials.

Flammability and Explosibility

Nonflammable

Safety Profile

Poison by intravenous and intratracheal routes. Moderately toxic by subcutaneous route. Experimental reproductive effects. A powerful oxidizer. Flammable by chemical reaction. It must not be heated or rubbed in contact with easily oxilzable matter. Violent thermite reaction when heated with aluminum. Potentially explosive reaction with hydrogen peroxide, peroxomonosulfuric acid, chlorates + heat, anilinium perchlorate. Ignition on contact with hydrogen sulfide. Violent reaction with oxidizers, potassium azide (when warmed), diboron tetrafluoride, Incandescent reaction with calcium hydride, chlorine trifluoride, rubidium acetylide (at 350℃). Vigorous reaction with hydroxylaminium chloride. Incompatible with H202, H2SO j, Naz02. Keep away from heat and flammable materials. See also MANGANESE COMPOUNDS.

Potential Exposure

Manganese dioxide is used as depolarizer for dry cell batteries, for production of manganese metal; as an oxidizing agent; laboratory reagent; and in making pyrotechnics and matches; in dry cell batteries.

Shipping

UN1479 Oxidizing solid, n.o.s., Hazard Class: 5.1; Labels: 5.1-Oxidizer, Technical Name Required. UN3137 (powder) Oxidizing solid, flammable, Hazard Class: 5.1; Labels: 5.1-Oxidizer, 4.1 Flammable solid, Technical Name Required.

Incompatibilities

A powerful oxidizer. Incompatible with strong acids; reducing agents; combustible materials (such as fuel and clothing; organic materials. Mixtures with calcium hydride is a heat- and friction-sensitive explosive. Vigorous reaction with hydrogen sulfide, diboron tetrafluoride; calcium hydride; chlorine trifluoride; hydrogen peroxide; hydroxyaluminum chloride; anilinium perchlorate. Decomposes when heated above 553C producing manganese(III)oxide and oxygen, which increases fire hazard. Reacts violently with aluminum (thermite reaction), potassium azide; rubidium acetylide; in the presence of hea

Waste Disposal

Generators of waste (equal to or greater than 100 kg/mo) containing this contaminant, EPA hazardous waste number N450, must conform to USEPA regulations for storage, transportation, treatment, and disposal of waste. Dispose of waste material as hazardous waste using a licensed disposal contractor to an approved landfill. Dispose of contents and container to an approved waste disposal plant. Containers must be disposed of properly by following package label directions or by contacting your local or federal environmental control agency, or by contacting your regional EPA office. All federal, state, and local environmental regulations must be observed. Do not discharge into drains or sewers