Manganese

Description

Manganese occurs as a free element in nature and is ubiquitous in the environment. The origin and uses of this black mineral date back to the Greek golden period. Manganese was known as pyrolusite or manganese dioxide. A Swedish chemist, Carl Wilhelm Scheele, used pyrolusite to produce chlorine in the mid-eighteenth century. But not until 1774 was manganese isolated and purified as a metal by Johan Gottlieb Gahn by reducing the dioxide with carbon. Manganese is an essential element for humans and animals.

Chemical properties

Manganese is a combustible, lustrous, brittle, silvery soft metal. It may be found in chunks, powder, or flakes. The most important ore containing manganese is pyrolusite. Manganese may also be produced from ferrous scrap used in the production of electric and open-hearth steel.

Physical properties

Manganese is a reactive metal that has several oxidation states (2, 3, 4, 6, and 7) thatare responsible for its varied chemical compounds. The chemical and physical properties ofmanganese are similar to the properties of its companions in group 7—technetium (₄₃Tc) andrhenium (₇₅Re).Pure manganese is a gray-white metal that is somewhat similar to iron, located just to theright of it in period 4. Manganese is a reactive element that, over time, will decompose in coldwater and will rust (oxidize) in moist air. It has magnetic properties but is not as magnetic asiron. Its melting point is 1,233°C, its boiling point is 1962°C, and its density is 7.44 g/cm³.

Isotopes

There are 30 isotopes of manganese, ranging from Mn-44 to Mn-69, with onlyone being stable: Mn-55 makes up 100% of the element in the Earth’s crust. All theother isotopes are artificially radioactive with half-lives ranging from 70 nanoseconds to3.7×10⁶ years. Artificial radioisotopes are produced in nuclear reactors, and becausemost radioactive isotopes are not natural, they do not contribute to the element’s naturalexistence on Earth.

Origin of Name

The name manganese is derived from the mineral magnesite (or dolomite, a compound of magnesium carbonate), which was mined in the region of Magnesia of ancient Greece.

Occurrence

Manganese minerals are widely distributed across the Earth as oxides, silicates, and carbonates. Manganese is the 11th most abundant element found in the Earth’s crust, and manganeseoxide minerals are the 10th most abundant compounds in the Earth’s crust. Pure manganeseis found in meteorites that land on Earth’s surface. Its minerals psilomelane, pyrolusite, rhodichrosite, and manganite (manganese ore) are found in most countries. It is also found inlow-grade iron ores and in slag as a by-product of iron smelting. Manganese ores are foundin India, Brazil, the Republic of South Africa, Gabon, Australia, and Russia, as well as in thestate of Montana in the United States.Huge amounts (i.e., more than 10¹² tons) of manganese cover vast regions of the oceanbeds, and more than 10⁷ tons are newly deposited each year. When recovered nodules (lumps)are removed and dried, they contain between 15% and 35% Mn, which is below the requirement for commercial mining. In addition, smaller amounts of cobalt, nickel, and copper arefound in these manganese “nodules.” Proposals to mine the nodules have been suggested, butno large quantities have been recovered. Mining of the ocean floors for manganese will probably not occur until the sources on Earth become more scarce and expensive to exploit, whichis not likely to happen any time soon. Meanwhile, these nodule deposits serve as a reserve forseveral important metals.In addition to reduction of its ores in furnaces, manganese can be produced by electrolysis. The electrolyte is manganese sulfate that is produced by treating ore with sulfuric acid,(2MnO₂ + 2H₂SO₄ → 2MnSO₄ + O₂ + 2H₂O). The anode is lead alloy, and the cathode ismade of a steel alloy. Pure (about 99%) manganese metal collects at the cathode, and in theprocess, the manganese sulfate is converted back to sulfuric acid, which can be reused to reactwith more MnO₂ ore.

History

Recognized by Scheele, Bergman, and others as an element and isolated by Gahn in 1774 by reduction of the dioxide with carbon. Manganese minerals are widely distributed; oxides, silicates, and carbonates are the most common. The discovery of large quantities of manganese nodules on the floor of the oceans holds promise as a source of manganese. These nodules contain about 24% manganese together with many other elements in lesser abundance. Most manganese today is obtained from ores found in Ukraine, Brazil, Australia, Republic of So. Africa, Gabon, China, and India. Pyrolusite (MnO2) and rhodochrosite (MnCO3) are among the most common manganese minerals. The metal is obtained by reduction of the oxide with sodium, magnesium, aluminum, or by electrolysis. It is gray-white, resembling iron, but is harder and very brittle. The metal is reactive chemically, and decomposes in cold water slowly. Manganese is used to form many important alloys. In steel, manganese improves the rolling and forging qualities, strength, toughness, stiffness, wear resistance, hardness, and hardenability. With aluminum and antimony, especially with small amounts of copper, it forms highly ferromagnetic alloys. Manganese metal is ferromagnetic only after special treatment. The pure metal exists in four allotropic forms. The alpha form is stable at ordinary temperature; gamma manganese, which changes to alpha at ordinary temperatures, is soft, easily cut, and capable of being bent. The dioxide (pyrolusite) is used as a depolarizer in dry cells, and is used to “decolorize” glass that is colored green by impurities of iron. Manganese by itself colors glass an amethyst color, and is responsible for the color of true amethyst. The dioxide is also used in the preparation of oxygen and chlorine, and in drying black paints. The permanganate is a powerful oxidizing agent and is used in quantitative analysis and in medicine. Manganese is widely distributed throughout the animal kingdom. It is an important trace element and may be essential for utilization of vitamin B1. Twenty-seven isotopes and isomers are known. Manganese metal (99.95%) is priced at about $800/kg. Metal of 99.6% purity is priced at about $80/kg.

Characteristics

There are four allotropic forms of manganese, which means each of its allotropes has a different crystal form and molecular structure. Therefore, each allotrope exhibits different chemical and physical properties (see the forms of carbon—diamond, carbon black, and graphite).The alpha (α) allotrope is stable at room temperature whereas the gamma (γ) form is soft,bendable, and easy to cut. The delta ? allotrope exists only at temperatures above 1,100°C. Asa pure metal, it cannot be worked into different shapes because it is too brittle. Manganese isresponsible for the color in amethyst crystals and is used to make amethyst-colored glass.

The Uses of Manganese

In manufacture of steel; for rock crushers, railway points and crossings, wagon buffers; as a constituent of several alloys, e.g., ferromanganese, copper manganese, Manganin.

The Uses of Manganese

As an oligoelement, manganese plays a role in collagen synthesis and skin moisturizing. Patents have been assigned on the use of manganese, zinc, and copper in the treatment of acne and sunburns. It can also be used as a colorant, providing a violet color to a product.

The Uses of Manganese

Manganese is a metallic element that functions as a nutrient and dietary supplement. it is necessary for normal bone and tendon structure, central nervous system functionality, and glucose utiliza- tion. sources include manganese carbonate, chloride, oxides, and sulfates. these sources differ in solubility.

The Uses of Manganese

Manganese is a constituent of many alloys.It is used in the manufacture of steel. Certainmanganese compounds, such as, thefungicide, Maneb, the contrasting agent mangafodipirtrisodiumin nuclear magnetic resonancetomography for diagnostic imagingand the gasoline additive anti-knock agent,methylcyclopentadienyl manganese tricarbonyl(MMT) have been introduced into themarket in recent years.
Manganese is an essential trace elementneeded for many enzymatic reactions. Itsdeficiency is associated with growth retardation,changes in circulating HDL cholesteroland glucose levels and reproductive failure.Bone deformities have also been observedin certain animals deficient in manganese.Its deficiency, however is rarely found inhumans. Manganese is toxic at high dosesor chronic exposure. Manganese toxicity canoccur in certain occupational settings throughinhalation of its dust.

The Uses of Manganese

Manganese does not have many uses, but the utility it does have is important. Manganese’smajor use is as an alloy with other metals. When alloyed with iron, it makes steel that isstronger, stiffer, tougher, harder, and longer-wearing. At one time railroad rails were made ofiron and were replaced about once a year because of the “softness” of pure iron. Later it wasdiscovered that with the addition of about 20% manganese to iron, it was possible to producean extremely hard steel rail that would last over 20 years. When alloyed with aluminum, alongwith small amounts of antimony and copper, it forms a ferromagnetic alloy widely used inmany industries. Manganese dioxide (MnO₂, pyrolusite) is used as a depolarizer in dry cells (that’s the black “stuff” inside flashlight batteries). It is used as a drying agent in black paintsand varnishes and as a bleaching agent for glass and oils.Manganese is also used in the production of aluminum and other metals to produce light,impressively hard tools that can withstand high temperatures, such as the tools used to cutmetal on lathes.A small amount of manganese (1.5 to 5.0 milligrams) is required in the diets of humans fornormal development of tendon, bones, and some enzymes, and it is thought to be necessaryfor the body to utilize vitamin B1. Manganese is found in many foods, including peas, beans,bran, nuts, coffee, and tea.

Background

Manganese is a transition metal with a molar mass of 54.94g/mol. Manganese is considered critical for human health, and plays important roles in development, metabolism, and the antioxidant system. That said, excessive manganese intake is associated with manganism, a neurodegenerative disorder that causes dopaminergic neuronal death and parkinsonian-like symptoms.

Indications

Indicated for use as a supplement to intravenous solutions given for Total Parenteral Nutrition (TPN). Administration helps to maintain plasma levels and to prevent depletion of endogenous stores and subsequent deficiency symptoms.

Definition

A transition metal occurring naturally as oxides, e.g. pyrolusite (MnO₂). Nodules found on the ocean floor are about 25% manganese. Its main use is in alloy steels made by adding pyrolusite to iron ore in an electric furnace. Manganese decomposes cold water and dilute acids to give hydrogen and reacts with oxygen and nitrogen when heated. The oxidation states are +7, +6, +4, and (the most stable) +2. Manganese(II) salts are pale pink and with alkali the solutions precipitate manganese(II) hydroxide, which rapidly oxidizes in air to brown manganese(III) oxide. Symbol: Mn; m.p. 1244°C; b.p. 1962°C; r.d. 7.44 (20%C); p.n. 25; r.a.m. 54.93805.

Production Methods

World manganese ore production was estimated to be 13.3 million ton (as manganese) in 2008. Top five manganese-producing countries were South Africa, Australia, China, Gabon, and Brazil. World manganese ferroalloy production in 2008 was 13.2 million ton (MT) (10). Metallurgical applications account for most manganese consumption. In the United States, 85–90% of this is for steelmaking. Manganese is essential in iron and steel production because of its sulfur-fixing, deoxidizing, and alloying properties. As an alloying agent in finished steel, manganese contributes increased strength, hardness, and corrosion resistance. Practically all steels contain manganese; low-carbon steels contain 0.15–0.8% manganese, whereas high-strength steels contain over 1% manganese. Stainless steels typically contain about 1% manganese, but there are manganese-stainless steels (200 series stainless steels) where nickel is replaced partly or entirely by manganese, resulting in manganese content of 4–16%.

General Description

A lustrous brittle silvery solid.

Air & Water Reactions

During a fire in an industrial bag filter, a mixture of aluminum and Manganese dusts was released and an explosion resulted [Occ. Haz. 28:185-7. 1946-47].

Reactivity Profile

Manganese dust(finely divided) has been known to be pyrophoric. Powdered Manganese ignites in chlorine and burns brilliantly; with fluorine the reaction takes place with incandescence [Mellor 12:185, 344. 1946-47]. Concentrated nitric acid reacts with Manganese with incandescence and a feeble explosion [Mellor 12:188. 1946-47]. Manganese or potassium ignites in nitrogen dioxide [Ann. Chim. et Phys.(2) 2:317]. Manganese burns with a brilliant flame when heated in sulfur dioxide vapor [Mellor 12:187. 1946-47]. Contact with conc. hydrogen peroxide causes violent decomposition and/or ignition.

Hazard

Dust or powder is flammable. Use dry chemical to extinguish. Toxic. Central nervous system impairment. Questionable carcinogen.

Health Hazard

Couper in 1837 observed that manganesedust produced a neurological syndrome similarto those of Parkinson’s disease. Thesymptoms were muscle weakness, tremor,bent posture, excess salivation and whisperedspeech. Excess manganese can accumulatein brain tissue to cause such neurodegenerativedisorder known as manganism, a diseasewith Parkinson-like symptoms, evokingsevere psychiatric and extrapyramidal motorfunction. The clinical manifestation of suchtoxicity arises from the focal injury to basalganglia, a region characterized by intenseconsumption of oxygen and high dopaminecontent. Chronic manganese exposure probablyincurs mitochondrial dysfunction, depletionof levels of enzymes peroxidase andcatalase, as well as, biochemical imbalancesof catecholamine in this brain region. Suchexposures may eventually produce cytotoxiclevels of free radicals causing cellular damage.The mechanism of neurodegenerativedamage, however, is not clearly understood.Disturbances in iron homeostasis and valencestate of manganese have been cited as keyfactors in contributing to manganese toxicity(Crossgrove and Zheng 2004). Oxidativebasis of manganese neurotoxicity andprogression of manganism is well reviewed(HaMai and Bondy 2004; Dobson et al.2004; Levy and Nassetta 2003).
Yang et al (2005) have proposed an alternatepathway of manganese induced neurotoxicitythat involved eukaryotic ACDP(ancient conserved domain protein) familyprotein in metal homoeostasis. These authorsemployed the baker’s yeast Saccharomycescerevisiae as a model system to identifygenes that contributed to manganese-relateddamage.
The treatment against Mn toxicity includechelation therapy with EDTA and supplementationwith levodopa.

Flammability and Explosibility

Not classified

Agricultural Uses

Manganese (Mn) is a transition element with atomic number 25 and atomic weight 54.93. It belongs to Group 7 of the Periodic Table and is anessential plant nutrient which plays an important role in plant biochemical processes. It is absorbed by plants in the form of manganese ions (Mn²⁺) or as an organic complex. In green plants, manganese influences the light-dependent water splitting reaction (Hill reaction) and oxygen evolution during photosynthesis. Manganese provides oxygen to poorly ventilated interior soil pores, where iron in the form of ferrous ion (Fe²⁺) and complex organic molecules would otherwise remain nonoxidized.
Manganese is associated with several enzyme systems and electron transport. It exists as manganese ion (Mn²⁺) in plant cells in many complex forms. It can form metalloproteins and is tightly bound in chloroplast with its average concentration of 100 ppm in the plant cell.
Manganese serves as a co-factor or a prosthetic group of enzymes involved in reactions concerned with oxidation-reduction, carboxylation, decarboxylation, photophosphorylation and hydrolysis. It affects respiration, amino acid synthesis, lignin biosynthesis and hormone levels in plants. It regulates the metabolism of carbohydrates, proteins, nucleic acids, secondary metabolites, ascorbic acid and citric acid cycles. With other metals, it works in the activation of enzymes such as arginase, cysteine desulphydrase, deoxyribonuclease and yeast phosphatase. Manganese is a specific activator of the enzyme, namely, prolidase and glutamyl transferase.

Safety Profile

Human systemic effects by inhalation: degenerative brain changes, change in motor activity, muscle weakness. A skin and eye irritant. Questionable carcinogen with experimental tumorigenic data. Flammable and moderately explosive in the form of dust or powder when exposed to flame. The dust ma)' be pyrophoric in air and may explode when heated in carbon dioxide. Murtures of aluminum dust and manganese dust may explode in air. mxtures with ammonium nitrate may explode when heated. The powdered metal igmtes on contact with fluorine, chlorine + heat, hydrogen peroxide, bromine pentafluoride, sulfur dioxide + heat. Violent reaction with NO2 and oxidants. Incandescent reaction with phosphorus, nitryl fluoride, nitric acid. Wdl react with water or steam to produce hydrogen; can react with oxidizing materials. To fight fire, use special dry chemical. See also MANGANESE COMPOUNDS.

Potential Exposure

Manganese is used in the production of steel; and in the manufacture of welding rod coatings and fluxes; in the iron and steel industry in steel alloys, e.g., ferro-manganese, silico-manganese, manganin, spiegeleisen; and as an agent to reduce oxygen and sulfur content of molten steel. Other alloys may be formed with copper, zinc, and aluminum. Manganese and its compounds are utilized in the manufacture of dry cell batteries (MnO2), paints, varnishes, inks, dyes, matches, and firework; as a fertilizer, disinfectant, bleaching agent; laboratory reagent; drier for oils; an oxidizing agent in the chemical industry particularly in the synthesis of potassium permanganate; and as a decolorizer and coloring agent in the glass and ceramics industry. Exposure may occur during the mining, smelting, and refining of manganese; in the production of various materials; and in welding operations with manganese-coated rods. Manganese normally is ingested as a trace nutrient in food. The average human intake is approximately 10 mg/day

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 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. The symptoms of metal fume fever may be delayed for 412 h following exposure: it may last less than 36 h. Medical observation is recommended.

Environmental Fate

Higher levels of environmental exposures to manganese are most likely to occur in or near a factory or a waste site that releases manganese dust into air. Manganese is also released into air by combustion of unleaded gasoline that contains manganese as an antiknock ingredient. Some manganese compounds are readily soluble, so significant exposures can also occur by ingestion of contaminated drinking water. However, manganese in surface water may oxidize or adsorb to sediment particles and settle out. Manganese in soil can migrate as particulate matter to air or water, or soluble compounds may be dissolved by water and leached from the soil. Elemental manganese and inorganic manganese compounds have negligible vapor pressures, but may exist in air as suspended particulate matter derived from industrial emissions or the erosion of soils. The half-life of airborne particles is usually on the order of days, depending on the size of the particle and atmospheric conditions.
The transport and partitioning of manganese in water are controlled by the solubility of the specific chemical form present, which in turn is determined by pH, Eh (oxidation–reduction potential), and the characteristics of available anions. The metal may exist in water in any of four oxidation states (2+, 3+, 4+, or 7+). Divalent manganese (Mn2+) predominates in most waters (pH 4–7), but may become oxidized at pH greater than 8 or 9. The principal anion associated with Mn2+ in water is usually carbonate (CO3 2), and the concentration of manganese is limited by the relatively low solubility (65 mg l^-1) of MnCO2. In relatively oxidized water, the solubility of Mn2+ may be controlled by manganese oxide equilibria, with manganese being converted to the (3+) or (4+) valence state. In extremely reduced water, the fate of manganese tends to be controlled by the formation of the poorly soluble sulfide.
Manganese in water may be significantly bioconcentrated at lower trophic levels.
Manganese is a natural component ofmost foods. The highest manganese concentrations (up to 40 ppm) are found in nuts and grains, with lower levels (up to 4 ppm) found in milk products, meats, fish, and eggs. Concentrations of manganese in infant formulas range from 34 to 1000 ppb, compared to concentrations of 10 ppb in human milk and 30 ppb in cow’s milk.

Metabolism

Not Available

storage

Color Code—Green: General storage may be used. Prior to working with this chemical you should be trained on its proper handling and storage. Manganese must be stored to avoid contact with water and steam since flammable hydrogen gas is produced. Store in tightly closed containers in a cool, well-ventilated area away from oxidizers (such as perchlorates, peroxides, permanganates, chlorates and nitrates). Protect storage against physical damage.

Shipping

UN3089 Metal powders, flammable, n.o.s., Hazard Class: 4.1; Labels: 4.1-Flammable solid. UN3077Environmentally hazardous substances, solid, n.o.s., Hazard class: 9; Labels: 9-Miscellaneous hazardous material, Technical Name Required

Toxicity evaluation

Manganese [7439-96-5] is an integral part of the superoxide dismutase and of the electron donor complex of photosystem II. Manganese may activate enzymes in the same way as Mg2+ by bridging the phosphate group with the enzyme or the substrate. Deficiency of Mn2+ leads to the breakdown of chloroplasts. Characteristic deficiency symptoms are smaller yellow spots on the leaves and interveinal chlorosis. Manganese toxicity may occur, especially on flooded soils, because of the reduction and thus solubilization of manganese oxides. Toxicity symptoms are generally characterized by brown spots of MnO2 in the older leaves surrounded by chlorotic areas (29).

Incompatibilities

Dust, powder, or finely divided material has been known to be pyrophoric or explosive in air. Compact, solid metallic magnesium is nonflammable. Reacts with water (slowly), steam, or acid producing flammable hydrogen gas. Reacts violently with concentrated hydrogen peroxide. Incompatible with nitrogen gas above 200C. Oxidizers, nitric acid; nitrogen, finely divided aluminum and other metals; sulfur dioxide; carbon dioxide 1 heat may cause fire and explosions

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. Manganese metal-sanitary landfill. Manganese chloride or sulfate-chemical conversion to the oxide followed by land filling, or conversion to the sulfate for use in fertilizer. Consult with environmental regulatory agencies for guidance on acceptable disposal practices.