Manganese dioxide

Description

Manganese dioxide, mainly used as a depolarizer in dry cell batteries, is the most important non-metallic form of manganese. In either traditional alkaline and rechargeable battery cells, Manganese dioxide takes in electrons through a redox reaction, becoming Manganese III oxide. It also has applications in lithium-ion technologies.
It is also the primary precursor to ferromanganese, an alloy of iron used for its lower melting point and low cost.
It is black in appearance and used to color glass and ceramics, as well as for cave art and possibly body paint in prehistorical eras. Further uses include the purification of drinking water, and production of pure oxygen and chlorine.

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.

Resources

https://www.hindawi.com/journals/jnm/2013/736375/
https://b2bbusinessnews.wordpress.com/2012/03/22/uses-and-benefits-of-manganese-dioxide/
http://metalpedia.asianmetal.com/metal/manganese/application.shtml
https://www.chemistryworld.com/podcasts/manganese-dioxide/9217.article
https://en.wikipedia.org/wiki/Manganese_dioxide
https://en.wikipedia.org/wiki/Ferroalloy

Description

Manganese dioxide is a black crystalline solid. Molecular weight= 86.94; Freezing/Melting point=(decomposes)=53℃. Hazard Identification (based on NFPA-704 M Rating System): Health 3, Flammability 0, Reactivity×(Oxidizer). Insoluble in water.

Chemical Properties

Manganese dioxide is a black crystalline solid or powder.

Physical properties

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

Uses

Manganese(IV) oxide is the most important ore of manganese from which the metal is mostly manufactured. The oxide occurs in nature as the mineral pyrolusite as heavy gray lumps, or black when powdered.
The mineral is used to produce manganese metal, most manganese salts, and also manganese steel and other alloys. The metallurgical applications of manganese(IV) oxide mainly involve making ferromanganese and special manganese alloys. Another important application of manganese(IV) oxide is in manufacturing dry-cell batteries and alkaline cells. The oxide also is a colorant in brick, tile, porcelain and glass; a drier for paints and varnishes; a 552 MANGANESE(IV) OXIDEpreparation for printing and dyeing textiles; a curing agent for polysulfide rubbers; an adsorbent for hydrogen sulfide and sulfur dioxide; an oxidizing agent in many organic syntheses such as quinone and hydroquinone; and a catalyst in laboratory preparation of oxygen from potassium chlorate. Manganese(IV) oxide also is used to make welding rods and fluxes, and ceramic magnets (ferrites); and is an additive to fertilizers.

Uses

The mineral is the source of manganese and all its Compounds; largely used in manufacture of manganese steel; oxidizer; in alkaline batteries (dry cells); for making amethyst glass, decolorizing glass; painting on porcelain, faience and majolica. The ppt is used in electrotechnics, pigments, browning gun barrels, drier for paints and varnishes, printing and dyeing textiles.

Uses

As an oxidizing agent, source of metallic manganese, decolorizing glass, painting porcelain, as an analytical reagentManganese(IV) oxide is used as an oxidizing agent in organic synthesis such as oxidation of allylic/benzylic alcohols, as a textile dye, as a reducing agent, and as a component of dry cell batteries such as zinc-carbon battery and alkaline battery. It is also used in making pigments for glasses and ceramics, and drier for paints. Further it is used in the manufacture of manganese steel and several manganese derivatives including potassium permanganate, a powerful versatile oxidant. Catalytic hydration of nitriles to amides by flowing through manganese dioxide has been reported. Manganese dioxide supported on inorganic oxide can be used for oxidation of methylamine through CWAO (Catalytic Wet Air Oxidation). It has high potential as highly efficient and robust material for water oxidation reaction (WORs).

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 + ½ 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.

General Description

Manganese(IV) oxide (MnO₂) is an eco-friendly chemical having a high theoretical specific capacitance.

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

Non flammable

Industrial uses

Manganese dioxide (MnO₂) is soluble in water and HNO₃ and soluble in HCl. It occurs in nature as the blue-black mineral pyrolusite. In glass, manganese dioxide is used as a colorant and decolorizer.
The major use of manganese oxides is an ore of manganese for the manufacturing of steel; manganese serves to increase the hardness and decrease the brittleness of steel. Another important use of manganese oxides is as the cathode material of common zinc/carbon and alkaline batteries (such as flashlight batteries).

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.

First aid

If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if Manganese dioxide 1665 heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit.

storage

Color Code—Yellow: Reactive Hazard (strong oxidizer); Store in a location separate from other materials, especially flammables and combustibles. Prior to working with this chemical you should be trained on its proper handling and storage. Manganese dioxide must be stored to avoid contact with heat and flammable materials and oxidizers (such as perchlorates, peroxides, permanganates, chlorates, and nitrates), since violent reactions occur. See also incompatibilities above. See OSHA Standard 1910.104 and NFPA 43A Code for the Storage of Liquid and Solid Oxidizers for detailed handling and storage regulations.

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