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molybdenum
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{{short description|chemical element with atomic number 42}}







factoids
Molybdenum is a chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin molybdaenum, from Ancient Greek {{transl|grc|molybdos}}, meaning lead, since its ores were confused with lead ores.BOOK, Molybdenum, 1994, CRC Handbook of Chemistry and Physics, 4, 18, Chemical Rubber Publishing Company, 978-0-8493-0474-3, Lide, David R., Molybdenum minerals have been known throughout history, but the element was discovered (in the sense of differentiating it as a new entity from the mineral salts of other metals) in 1778 by Carl Wilhelm Scheele. The metal was first isolated in 1781 by Peter Jacob Hjelm.WEB,weblink It's Elemental - The Element Molybdenum, education.jlab.org, en-us, 2018-07-03,weblink 2018-07-04, live, Molybdenum does not occur naturally as a free metal on Earth; it is found only in various oxidation states in minerals. The free element, a silvery metal with a gray cast, has the sixth-highest melting point of any element. It readily forms hard, stable carbides in alloys, and for this reason most of world production of the element (about 80%) is used in steel alloys, including high-strength alloys and superalloys.Most molybdenum compounds have low solubility in water, but when molybdenum-bearing minerals contact oxygen and water, the resulting molybdate ion {{chem|MoO|4|2-}} is quite soluble. Industrially, molybdenum compounds (about 14% of world production of the element) are used in high-pressure and high-temperature applications as pigments and catalysts.{{c|Molybdenum enzymes|Molybdenum-bearing enzymes}} are by far the most common bacterial catalysts for breaking the chemical bond in atmospheric molecular nitrogen in the process of biological nitrogen fixation. At least 50 molybdenum enzymes are now known in bacteria, plants, and animals, although only bacterial and cyanobacterial enzymes are involved in nitrogen fixation. These nitrogenases contain molybdenum in a form different from other molybdenum enzymes, which all contain fully oxidized molybdenum in a molybdenum cofactor. These various molybdenum cofactor enzymes are vital to the organisms, and molybdenum is an essential element for life in all higher eukaryote organisms, though not in all bacteria.

Characteristics

Physical properties

In its pure form, molybdenum is a silvery-grey metal with a Mohs hardness of 5.5 and a standard atomic weight of 95.95 g/mol.JOURNAL, Wieser, M. E., Berglund, M., 2009, Atomic weights of the elements 2007 (IUPAC Technical Report),weblink Pure and Applied Chemistry, 81, 11, 2131–2156, 10.1351/PAC-REP-09-08-03, 2012-02-13,weblink" title="web.archive.org/web/20120311194819weblink">weblink 2012-03-11, live, WEB,weblink Current Table of Standard Atomic Weights in Alphabetical Order: Standard Atomic weights of the elements, 2013, Meija, Juris, etal, Commission on Isotopic Abundances and Atomic Weights, bot: unknown,weblink" title="web.archive.org/web/20140429050401weblink">weblink 2014-04-29, It has a melting point of {{convert|2623|°C|°F}}; of the naturally occurring elements, only tantalum, osmium, rhenium, tungsten, and carbon have higher melting points. It has one of the lowest coefficients of thermal expansion among commercially used metals.BOOK, Emsley, John, Nature's Building Blocks,weblink Oxford University Press, 2001, Oxford, 262–266, 978-0-19-850341-5,

Chemical properties

Molybdenum is a transition metal with an electronegativity of 2.16 on the Pauling scale. It does not visibly react with oxygen or water at room temperature. Weak oxidation of molybdenum starts at {{convert|300|°C|°F}}; bulk oxidation occurs at temperatures above 600 Â°C, resulting in molybdenum trioxide. Like many heavier transition metals, molybdenum shows little inclination to form a cation in aqueous solution, although the Mo3+ cation is known under carefully controlled conditions.BOOK, Parish, R. V., 1977, The Metallic Elements,weblink registration, New York, Longman, 112, 133, 978-0-582-44278-8,

Isotopes

There are 35 known isotopes of molybdenum, ranging in atomic mass from 83 to 117, as well as four metastable nuclear isomers. Seven isotopes occur naturally, with atomic masses of 92, 94, 95, 96, 97, 98, and 100. Of these naturally occurring isotopes, only molybdenum-100 is unstable.{{NUBASE 2003}}Molybdenum-98 is the most abundant isotope, comprising 24.14% of all molybdenum. Molybdenum-100 has a half-life of about 1019 y and undergoes double beta decay into ruthenium-100. Molybdenum isotopes with mass numbers from 111 to 117 all have half-lives of approximately 150 ns. All unstable isotopes of molybdenum decay into isotopes of niobium, technetium, and ruthenium.BOOK, 2006, CRC Handbook of Chemistry and Physics, Lide, David R., 11, 87–88, CRC, 978-0-8493-0487-3, The most common isotopic molybdenum application involves molybdenum-99, which is a fission product. It is a parent radioisotope to the short-lived gamma-emitting daughter radioisotope technetium-99m, a nuclear isomer used in various imaging applications in medicine.MAGAZINE, Armstrong, John T.,weblink Technetium, Chemical & Engineering News, 2003, 2009-07-07,weblink" title="web.archive.org/web/20081006002652weblink">weblink 2008-10-06, live, In 2008, the Delft University of Technology applied for a patent on the molybdenum-98-based production of molybdenum-99.Wolterbeek, Hubert Theodoor; Bode, Peter "A process for the production of no-carrier added 99Mo". European Patent EP2301041 (A1) ― 2011-03-30. Retrieved on 2012-06-27.

Compounds

{{Category see also|Molybdenum compounds}}Molybdenum forms chemical compounds in oxidation states from -II to +VI. Higher oxidation states are more relevant to its terrestrial occurrence and its biological roles, mid-level oxidation states are often associated with metal clusters, and very low oxidation states are typically associated with organomolybdenum compounds. Mo and W chemistry shows strong similarities. The relative rarity of molybdenum(III), for example, contrasts with the pervasiveness of the chromium(III) compounds. The highest oxidation state is seen in molybdenum(VI) oxide (MoO3), whereas the normal sulfur compound is molybdenum disulfide MoS2.{|class="wikitable" style="float:left; margin-right: 1em;"!Oxidation state!ExampleBOOK, Anorganische Chemie II., VI. Nebengruppe, 119–127, Max, Schmidt, Wissenschaftsverlag, 1968, German,
Na[Mo(CO)]}}
}}
Na[CHMo]}}
Molybdenum(II) chloride>{{chem2}}
Na[Mo(CN)]|6}}
+4>Molybdenum disulfide>{{chem2}}
Molybdenum(V) chloride>{{chem5}}
+6>Molybdenum(VI) fluoride>{{chem6}}
File:Phosphotungstate-3D-polyhedra.png|thumb|upright|Keggin structure of the phosphomolybdate anion (P[Mo12O40]3−), an example of a polyoxometalatepolyoxometalateFrom the perspective of commerce, the most important compounds are molybdenum disulfide ({{chem|MoS|2}}) and molybdenum trioxide ({{chem|MoO|3}}). The black disulfide is the main mineral. It is roasted in air to give the trioxide:
2 {{chem|MoS|2}} + 7 {{chem|O|2}} → 2 {{chem|MoO|3}} + 4 {{chem|SO|2}}
The trioxide, which is volatile at high temperatures, is the precursor to virtually all other Mo compounds as well as alloys. Molybdenum has several oxidation states, the most stable being +4 and +6 (bolded in the table at left).Molybdenum(VI) oxide is soluble in strong alkaline water, forming molybdates (MoO42−). Molybdates are weaker oxidants than chromates. They tend to form structurally complex oxyanions by condensation at lower pH values, such as [Mo7O24]6− and [Mo8O26]4−. Polymolybdates can incorporate other ions, forming polyoxometalates.JOURNAL, Angewandte Chemie International Edition, 30, 34–48, 1997, Polyoxometalate Chemistry: An Old Field with New Dimensions in Several Disciplines, Michael T., Pope, Müller, Achim, 10.1002/anie.199100341, The dark-blue phosphorus-containing heteropolymolybdate P[Mo12O40]3− is used for the spectroscopic detection of phosphorus.BOOK, 978-0-8247-8433-1, 280–288, Nollet, Leo M. L., 2000, Marcel Dekker, New York, NY, Handbook of water analysis,weblink The broad range of oxidation states of molybdenum is reflected in various molybdenum chlorides: Molybdenum(VI) chloride MoCl6 is not known, although the molybdenum hexafluoride is well characterized.Like chromium and some other transition metals, molybdenum forms quadruple bonds, such as in Mo2(CH3COO)4 and [Mo2Cl8]4−, which also has a quadruple bond.BOOK, Inorganic Syntheses: Volume 36, Walton, Richard A., Fanwick, Phillip E., Girolami, Gregory S., Murillo, Carlos A., Johnstone, Erik V., 2014, John Wiley & Sons, Inc., 9781118744994, Girolami, Gregory S., 78–81, en, 10.1002/9781118744994.ch16, Sattelberger, Alfred P., The oxidation state 0 is possible with carbon monoxide as ligand, such as in molybdenum hexacarbonyl, Mo(CO)6.

History

Molybdenite—the principal ore from which molybdenum is now extracted—was previously known as molybdena. Molybdena was confused with and often utilized as though it were graphite. Like graphite, molybdenite can be used to blacken a surface or as a solid lubricant.BOOK, Lansdown, A. R., Molybdenum disulphide lubrication, 35, Tribology and Interface Engineering, Elsevier, 1999, 978-0-444-50032-8, Even when molybdena was distinguishable from graphite, it was still confused with the common lead ore PbS (now called galena); the name comes from Ancient Greek , meaning lead. (The Greek word itself has been proposed as a loanword from Anatolian Luvian and Lydian languages).WEB, Melchert, Craig,weblink Greek mólybdos as a Loanword from Lydian, University of North Carolina at Chapel Hill, North Carolina, Chapel Hill, 2011-04-23,weblink" title="web.archive.org/web/20131231000505weblink">weblink 2013-12-31, live, Although (reportedly) molybdenum was deliberately alloyed with steel in one 14th-century Japanese sword (mfd. ca. 1330), that art was never employed widely and was later lost.International Molybdenum Association, weblink" title="web.archive.org/web/20130722102351weblink">"Molybdenum History"BOOK, Accidental use of molybdenum in old sword led to new alloy,weblink Institute, American Iron and Steel, 1948, In the West in 1754, Bengt Andersson Qvist examined a sample of molybdenite and determined that it did not contain lead and thus was not galena.WEB, Van der Krogt, Peter, Molybdenum, Elementymology & Elements Multidict, 2006-01-10,weblink 2007-05-20,weblink" title="web.archive.org/web/20100123002743weblink">weblink 2010-01-23, live, By 1778 Swedish chemist Carl Wilhelm Scheele stated firmly that molybdena was (indeed) neither galena nor graphite.WEB, Gagnon, Steve, Molybdenum, Jefferson Science Associates, LLC,weblink 2007-05-06,weblink" title="web.archive.org/web/20070426150528weblink">weblink 2007-04-26, live, JOURNAL, Scheele, C. W. K., Versuche mit Wasserbley;Molybdaena, Svenska Vetensk. Academ. Handlingar, 238, 1779, 40,weblink Instead, Scheele correctly proposed that molybdena was an ore of a distinct new element, named molybdenum for the mineral in which it resided, and from which it might be isolated. Peter Jacob Hjelm successfully isolated molybdenum using carbon and linseed oil in 1781.JOURNAL, Hjelm, P. J., Versuche mit Molybdäna, und Reduction der selben Erde, Svenska Vetensk. Academ. Handlingar, 268, 1788, 49,weblink For the next century, molybdenum had no industrial use. It was relatively scarce, the pure metal was difficult to extract, and the necessary techniques of metallurgy were immature.BOOK, Hoyt, Samuel Leslie, Metallography, 2, McGraw-Hill, 1921, BOOK, Krupp, Alfred, Wildberger, Andreas, The metallic alloys: A practical guide for the manufacture of all kinds of alloys, amalgams, and solders, used by metal-workers ... with an appendix on the coloring of alloys, H.C. Baird & Co., 1888, 60, BOOK, Gupta, C. K., Extractive Metallurgy of Molybdenum, CRC Press, 1992, 978-0-8493-4758-0, Early molybdenum steel alloys showed great promise of increased hardness, but efforts to manufacture the alloys on a large scale were hampered with inconsistent results, a tendency toward brittleness, and recrystallization. In 1906, William D. Coolidge filed a patent for rendering molybdenum ductile, leading to applications as a heating element for high-temperature furnaces and as a support for tungsten-filament light bulbs; oxide formation and degradation require that molybdenum be physically sealed or held in an inert gas.BOOK,weblink 117, The Making of American Industrial Research: Science and Business at Ge and Bell, 1876–1926, 9780521522373, Reich, Leonard S., 2002-08-22, 2016-04-07,weblink" title="web.archive.org/web/20140709171645weblink">weblink 2014-07-09, live, In 1913, Frank E. Elmore developed a froth flotation process to recover molybdenite from ores; flotation remains the primary isolation process.BOOK,weblink 3, Molybdenum deposits of Canada, Vokes, Frank Marcus, 1963, During World War I, demand for molybdenum spiked; it was used both in armor plating and as a substitute for tungsten in high speed steels. Some British tanks were protected by 75 mm (3 in) manganese steel plating, but this proved to be ineffective. The manganese steel plates were replaced with much lighter {{Convert|25|mm|inch|1|abbr=on}} molybdenum steel plates allowing for higher speed, greater maneuverability, and better protection. The Germans also used molybdenum-doped steel for heavy artillery, like in the super-heavy howitzer Big Bertha,Chemical properties of molibdenum - Health effects of molybdenum - Environmental effects of molybdenum {{Webarchive|url=https://web.archive.org/web/20160120203530weblink |date=2016-01-20 }}. lenntech.com because traditional steel melts at the temperatures produced by the propellant of the one ton shell.Sam Kean. The Disappearing Spoon. Page 88–89 After the war, demand plummeted until metallurgical advances allowed extensive development of peacetime applications. In World War II, molybdenum again saw strategic importance as a substitute for tungsten in steel alloys.JOURNAL, Ray, Millholland, Battle of the Billions: American industry mobilizes machines, materials, and men for a job as big as digging 40 Panama Canals in one year, August 1941, Popular Science, 61,weblink 2016-04-07,weblink" title="web.archive.org/web/20140709161654weblink">weblink 2014-07-09, live,

Occurrence and production

File:Molly Hill molybdenite.JPG|thumb|alt=Lustrous, silvery, flat, hexagonal crystals in roughly parallel layers sit flowerlike on a rough, translucent crystalline piece of quartz.|MolybdeniteMolybdeniteMolybdenum is the 54th most abundant element in the Earth's crust with an average of 1.5 parts per million and the 25th most abundant element in its oceans, with an average of 10 parts per billion; it is the 42nd most abundant element in the Universe.BOOK, Molybdenum, 2005, Van Nostrand's Encyclopedia of Chemistry, 1038–1040, New York, Wiley-Interscience, 978-0-471-61525-5, Considine, Glenn D., The Russian Luna 24 mission discovered a molybdenum-bearing grain (1 × 0.6 Âµm) in a pyroxene fragment taken from Mare Crisium on the Moon.JOURNAL,weblink New mineral names, American Mineralogist, 87, 181, 2002, Jambor, J.L., etal, 2007-04-09,weblink" title="web.archive.org/web/20070710054017weblink">weblink 2007-07-10, live, The comparative rarity of molybdenum in the Earth's crust is offset by its concentration in a number of water-insoluble ores, often combined with sulfur in the same way as copper, with which it is often found. Though molybdenum is found in such minerals as wulfenite (PbMoO4) and powellite (CaMoO4), the main commercial source is molybdenite (MoS2). Molybdenum is mined as a principal ore and is also recovered as a byproduct of copper and tungsten mining.The world's production of molybdenum was 250,000 tonnes in 2011, the largest producers being China (94,000 t), the United States (64,000 t), Chile (38,000 t), Peru (18,000 t) and Mexico (12,000 t). The total reserves are estimated at 10 million tonnes, and are mostly concentrated in China (4.3 Mt), the US (2.7 Mt) and Chile (1.2 Mt). By continent, 93% of world molybdenum production is about evenly shared between North America, South America (mainly in Chile), and China. Europe and the rest of Asia (mostly Armenia, Russia, Iran and Mongolia) produce the remainder.(File:Molybdenum world production.svg|thumb|World production trend)In molybdenite processing, the ore is first roasted in air at a temperature of {{convert|700|°C|°F}}. The process gives gaseous sulfur dioxide and the molybdenum(VI) oxide:
2 MoS2 + 7 O2 → 2 MoO3 + 4 SO2
The oxidized ore is then usually extracted with aqueous ammonia to give ammonium molybdate:
MoO3 + 2 NH3 + H2O → (NH4)2(MoO4)
Copper, an impurity in molybdenite, is less soluble in ammonia. To completely remove it from the solution, it is precipitated with hydrogen sulfide. Ammonium molybdate converts to ammonium dimolybdate, which is isolated as a solid. Heating this solid gives molybdenum trioxide:Sebenik, Roger F. et al. (2005) "Molybdenum and Molybdenum Compounds" in Ullmann's Encyclopedia of Chemical Technology. Wiley-VCH, Weinheim. {{DOI|10.1002/14356007.a16_655}}
(NH4)2Mo2O7 → 2 MoO3 + 2 NH3 + H2O
Crude trioxide can be further purified by sublimation at {{convert|1100|°C|°F}}.Metallic molybdenum is produced by reduction of the oxide with hydrogen:
MoO3 + 3 H2 → Mo + 3 H2O
The molybdenum for steel production is reduced by the aluminothermic reaction with addition of iron to produce ferromolybdenum. A common form of ferromolybdenum contains 60% molybdenum.BOOK, Walter de Gruyter, 1985, 91–100, 1096–1104, 978-3-11-007511-3, Lehrbuch der Anorganischen Chemie, Holleman, Arnold F., Wiberg, Egon, Wiberg, Nils, BOOK, Gupta, C. K., Extractive Metallurgy of Molybdenum, CRC Press, 1992, 1–2, 978-0-8493-4758-0, Molybdenum had a value of approximately $30,000 per tonne as of August 2009. It maintained a price at or near $10,000 per tonne from 1997 through 2003, and reached a peak of $103,000 per tonne in June 2005.WEB, Dynamic Prices and Charts for Molybdenum, InfoMine Inc., 2007,weblink 2007-05-07,weblink" title="web.archive.org/web/20091008202153weblink">weblink 2009-10-08, live, In 2008, the London Metal Exchange announced that molybdenum would be traded as a commodity.WEB, LME to launch minor metals contracts in H2 2009,weblink 2008-09-04, London Metal Exchange, 2009-07-28, bot: unknown,weblink" title="web.archive.org/web/20120722014344weblink">weblink 2012-07-22,

History of molybdenum mining

Historically, the Knaben mine in southern Norway, opened in 1885, was the first dedicated molybdenum mine. It was closed in 1973 but was reopened in 2007.JOURNAL, 10.1016/S0375-6742(96)00069-6, Dispersion of tailings in the Knabena—Kvina drainage basin, Norway, 1: Evaluation of overbank sediments as sampling medium for regional geochemical mapping, 1997, Langedal, M., Journal of Geochemical Exploration, 58, 157–172, 2–3, and now produces {{Convert|100000|kg|ton|0}} of molybdenum disulfide per year. Large mines in Colorado (such as the Henderson mine and the Climax mine)JOURNAL, Paul B., Coffman, The Rise of a New Metal: The Growth and Success of the Climax Molybdenum Company, The Journal of Business of the University of Chicago, 30, 1937, 10, 10.1086/232443, and in British Columbia yield molybdenite as their primary product, while many porphyry copper deposits such as the Bingham Canyon Mine in Utah and the Chuquicamata mine in northern Chile produce molybdenum as a byproduct of copper mining.

Applications

Alloys

(File:Plate of Molybdenum Copper .jpg|thumb|A plate of molybdenum copper alloy)About 86% of molybdenum produced is used in metallurgy, with the rest used in chemical applications. The estimated global use is structural steel 35%, stainless steel 25%, chemicals 14%, tool & high-speed steels 9%, cast iron 6%, molybdenum elemental metal 6%, and superalloys 5%.weblink" title="web.archive.org/web/20120310004452weblink">Pie chart of world Mo uses. London Metal Exchange.Molybdenum can withstand extreme temperatures without significantly expanding or softening, making it useful in environments of intense heat, including military armor, aircraft parts, electrical contacts, industrial motors, and supports for filaments in light bulbs.Most high-strength steel alloys (for example, 41xx steels) contain 0.25% to 8% molybdenum. Even in these small portions, more than 43,000 tonnes of molybdenum are used each year in stainless steels, tool steels, cast irons, and high-temperature superalloys.Molybdenum is also valued in steel alloys for its high corrosion resistance and weldability.WEB, Molybdenum Statistics and Information, U.S. Geological Survey, 2007-05-10,weblink 2007-05-10,weblink" title="web.archive.org/web/20070519151353weblink">weblink 2007-05-19, live, Molybdenum contributes corrosion resistance to type-300 stainless steels (specifically type-316) and especially so in the so-called superaustenitic stainless steels (such as alloy AL-6XN, 254SMO and 1925hMo). Molybdenum increases lattice strain, thus increasing the energy required to dissolve iron atoms from the surface.{{contradict-inline|date=September 2018}} Molybdenum is also used to enhance the corrosion resistance of ferritic (for example grade 444) and martensitic (for example 1.4122 and 1.4418) stainless steels.{{citation needed|date=December 2014}}Because of its lower density and more stable price, molybdenum is sometimes used in place of tungsten. An example is the 'M' series of high-speed steels such as M2, M4 and M42 as substitution for the 'T' steel series, which contain tungsten. Molybdenum can also be used as a flame-resistant coating for other metals. Although its melting point is {{convert|2623|°C|°F|abbr=on}}, molybdenum rapidly oxidizes at temperatures above {{convert|760|°C|°F|abbr=on}} making it better-suited for use in vacuum environments.WEB, Molybdenum, AZoM.com Pty. Limited, 2007,weblink 2007-05-06,weblink" title="web.archive.org/web/20110614171110weblink">weblink 2011-06-14, live, TZM (Mo (~99%), Ti (~0.5%), Zr (~0.08%) and some C) is a corrosion-resisting molybdenum superalloy that resists molten fluoride salts at temperatures above {{convert|1300|°C|°F|abbr=on}}. It has about twice the strength of pure Mo, and is more ductile and more weldable, yet in tests it resisted corrosion of a standard eutectic salt (FLiBe) and salt vapors used in molten salt reactors for 1100 hours with so little corrosion that it was difficult to measure.BOOK, Smallwood, Robert E., ASTM special technical publication 849: Refractory metals and their industrial applications: a symposium,weblink 1984, ASTM International, 9780803102033, 9, TZM Moly Alloy, WEB,weblink Compatibility of Molybdenum-Base Alloy TZM, with LiF-BeF2-ThF4-UF4, Oak Ridge National Laboratory Report, 2010-09-02, December 1969,weblink" title="web.archive.org/web/20110710192254weblink">weblink 2011-07-10, live, Other molybdenum-based alloys that do not contain iron have only limited applications. For example, because of its resistance to molten zinc, both pure molybdenum and molybdenum-tungsten alloys (70%/30%) are used for piping, stirrers and pump impellers that come into contact with molten zinc.BOOK, Tool and manufacturing engineers handbook, W. H., Cubberly, Bakerjian, Ramon, Society of Manufacturing Engineers, 978-0-87263-351-3,weblink 421, 1989,

Other applications as a pure element

  • Molybdenum powder is used as a fertilizer for some plants, such as cauliflower
  • Elemental molybdenum is used in NO, NO2, NOx analyzers in power plants for pollution controls. At {{convert|350|°C|°F|abbr=on}}, the element acts as a catalyst for NO2/NOx to form NO molecules for detection by infrared light.JOURNAL, 10.1023/A:1010730821844, 2001, Lal, S., Patil, R. S., Environmental Monitoring and Assessment, 68, 37–50, 11336410, Monitoring of atmospheric behaviour of NOx from vehicular traffic, 1,
  • Molybdenum anodes replace tungsten in certain low voltage X-ray sources for specialized uses such as mammography.BOOK, Physics of Medical X-Ray Imaging,weblink Ch. 4: Physical determinants of contrast, Lancaster, Jack L., University of Texas Health Science Center, dead,weblink" title="web.archive.org/web/20151010172937weblink">weblink 2015-10-10,
  • The radioactive isotope molybdenum-99 is used to generate technetium-99m, used for medical imagingGray, Theodore (2009). The Elements. Black Dog & Leventhal. pp. 105–107. {{ISBN|1-57912-814-9}}. The isotope is handled and stored as the molybdate.JOURNAL, 10.1146/annurev.me.20.020169.001023, 4894500, 1969, Gottschalk, A., Technetium-99m in clinical nuclear medicine, 20, 131–40, Annual Review of Medicine, 1,

Compounds (14% of global use)

  • Molybdenum disulfide (MoS2) is used as a solid lubricant and a high-pressure high-temperature (HPHT) anti-wear agent. It forms strong films on metallic surfaces and is a common additive to HPHT greases — in the event of a catastrophic grease failure, a thin layer of molybdenum prevents contact of the lubricated parts.JOURNAL, 10.1016/0043-1648(67)90187-1, Molybdenum disulfide as a lubricant: A review of the fundamental knowledge, 1967, Winer, W., Wear, 10, 422–452, 6, 2027.42/33266,weblink It also has semiconducting properties with distinct advantages over traditional silicon or graphene in electronics applications.WEB,weblink New transistors: An alternative to silicon and better than graphene, Physorg.com, January 30, 2011, 2011-01-30, MoS2 is also used as a catalyst in hydrocracking of petroleum fractions containing nitrogen, sulfur and oxygen.BOOK, Topsøe, H., Clausen, B. S., Massoth, F. E., Hydrotreating Catalysis, Science and Technology, Springer-Verlag, Berlin, 1996,
  • Molybdenum disilicide (MoSi2) is an electrically conducting ceramic with primary use in heating elements operating at temperatures above 1500 Â°C in air.BOOK,weblink 141, Electroceramics: materials, properties, applications, Moulson, A. J., Herbert, J. M., John Wiley and Sons, 2003, 978-0-471-49748-6,
  • Molybdenum trioxide (MoO3) is used as an adhesive between enamels and metals. Lead molybdate (wulfenite) co-precipitated with lead chromate and lead sulfate is a bright-orange pigment used with ceramics and plastics.International Molybdenum Association {{Webarchive|url=https://web.archive.org/web/20080309010036weblink |date=2008-03-09 }}. imoa.info.
  • The molybdenum-based mixed oxides are versatile catalysts in the chemical industry. Some examples are the catalysts for the selective oxidation of propylene to acrolein and acrylic acid, the ammoxidation of propylene to acrylonitrile.BOOK, Fierro, J. G. L., Metal Oxides, Chemistry and Applications, 2006, CRC Press, 414–455, BOOK, Centi, G., Cavani, F., Trifiro, F., Selective Oxidation by Heterogeneous Catalysis, 2001, Kluwer Academic/Plenum Publishers, 363–384, Suitable catalysts and process for the direct selective oxidation of propane to acrylic acid are being researched.WEB, Kinetic studies of propane oxidation on Mo and V based mixed oxide catalysts,weblink PhD Thesis, Technische Universität Berlin, Csepei, L.-I., 2011, 2016-12-04,weblink" title="web.archive.org/web/20161220044522weblink">weblink 2016-12-20, live, JOURNAL, The reaction network in propane oxidation over phase-pure MoVTeNb M1 oxide catalysts, Journal of Catalysis, March 2014, 311, 369–385, 10.1016/j.jcat.2013.12.008,weblink Naumann d'Alnoncourt, Raoul, Csepei, Lénárd-István, Hävecker, Michael, Girgsdies, Frank, Schuster, Manfred E., Schlögl, Robert, Trunschke, Annette, 2016-12-04,weblink" title="web.archive.org/web/20160215104605weblink">weblink 2016-02-15, dead, JOURNAL, Multifunctionality of Crystalline MoV(TeNb) M1 Oxide Catalysts in Selective Oxidation of Propane and Benzyl Alcohol, ACS Catalysis, 7 June 2013, 3, 6, 1103–1113, 10.1021/cs400010q,weblink Amakawa, Kazuhiko, Kolen'Ko, Yury V., Villa, Alberto, Schuster, Manfred E/, Csepei, Lénárd-István, Weinberg, Gisela, Wrabetz, Sabine, Naumann d'Alnoncourt, Raoul, Girgsdies, Frank, Prati, Laura, Schlögl, Robert, Trunschke, Annette, 4 December 2016,weblink 22 October 2018, live, JOURNAL, Surface chemistry of phase-pure M1 MoVTeNb oxide during operation in selective oxidation of propane to acrylic acid, Journal of Catalysis, January 2012, 285, 1, 48–60, 10.1016/j.jcat.2011.09.012,weblink Hävecker, Michael, Wrabetz, Sabine, Kröhnert, Jutta, Csepei, Lenard-Istvan, Naumann d'Alnoncourt, Raoul, Kolen'Ko, Yury V., Girgsdies, Frank, Schlögl, Robert, Trunschke, Annette, 11858/00-001M-0000-0013-FB1F-C, 2016-12-04,weblink" title="web.archive.org/web/20161030003154weblink">weblink 2016-10-30, dead,
  • Ammonium heptamolybdate is used in biological staining.
  • Molybdenum coated soda lime glass is used in CIGS (copper indium gallium selenide) solar cells, called CIGS solar cells.
  • Phosphomolybdic acid is a stain used in thin-layer chromatography.

Biological role

Mo-containing enzymes

Molybdenum is an essential element in most organisms; a 2008 research paper speculated that a scarcity of molybdenum in the Earth's early oceans may have strongly influenced the evolution of eukaryotic life (which includes all plants and animals).JOURNAL, Lyons, T. W., Bekker, A., Shen, Y., Poulton, S. W., Chu, X., Anbar, A. D., 2008, Tracing the stepwise oxygenation of the Proterozoic ocean, Nature, 452, 7186, 456–460, 2008Natur.452..456S, 10.1038/nature06811, 18368114, Scott, C., At least 50 molybdenum-containing enzymes have been identified, mostly in bacteria.JOURNAL, Synthetic Analogues and Reaction Systems Relevant to the Molybdenum and Tungsten Oxotransferases, Chem. Rev., 2004, 104, 1175–1200, 10.1021/cr020609d, John H., Enemark, J. Jon A., Cooney, Jun-Jieh, Wang, R. H., Holm, 14871153, 2, JOURNAL, 10.1016/j.bbamcr.2006.03.013, 621–635, 16784786, 2006, Mendel, Ralf R., Bittner, Florian, Cell biology of molybdenum, 1763, 7, Biochimica et Biophysica Acta, those enzymes include aldehyde oxidase, sulfite oxidase and xanthine oxidase. With one exception, Mo in proteins is bound by molybdopterin to give the molybdenum cofactor.JOURNAL, The Mononuclear Molybdenum Enzymes, Russ Hille, James Hall, Partha Basu, Chem. Rev., 2014, 114, 7, 3963–4038, 10.1021/cr400443z, 24467397, 4080432, In terms of function, molybdoenzymes catalyze the oxidation and sometimes reduction of certain small molecules in the process of regulating nitrogen, sulfur, and carbon.JOURNAL, A structural comparison of molybdenum cofactor-containing enzymes, FEMS Microbiol. Rev., 1999, 22, 10.1111/j.1574-6976.1998.tb00384.x, 9990727, 5, 503–521, Kisker, C., Schindelin, H., Baas, D., Rétey, J., Meckenstock, R. U., Kroneck, P. M. H.,weblink 2017-10-25,weblink 2017-08-10, live, In some animals, and in humans, the oxidation of xanthine to uric acid, a process of purine catabolism, is catalyzed by xanthine oxidase, a molybdenum-containing enzyme. The activity of xanthine oxidase is directly proportional to the amount of molybdenum in the body. However, an extremely high concentration of molybdenum reverses the trend and can act as an inhibitor in both purine catabolism and other processes. Molybdenum concentration also affects protein synthesis, metabolism, and growth.Mo is a component in most nitrogenases. Among molybdoenzymes, nitrogenases are unique in lacking the molybdopterin.RALF R. >LAST1=MENDELEDITOR1-LAST=BANCI VOLUME=12, Chapter 15 Metabolism of Molybdenumdate=2013 isbn=978-94-007-5560-4doi-broken-date=2019-08-20, electronic-book {{ISBN|978-94-007-5561-1}} {{issn|1559-0836}} electronic-{{issn|1868-0402}}BOOK, Lee, Chi Chung, Ribbe, Markus W., Hu, Yilin, Peter M.H. Kroneck, Martha E. Sosa Torres, The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment, Metal Ions in Life Sciences, 14, 2014, Springer, Chapter 7. Cleaving the N,N Triple Bond: The Transformation of Dinitrogen to Ammonia by Nitrogenases, 147–174, 10.1007/978-94-017-9269-1_6, 25416393, 978-94-017-9268-4,
Nitrogenases catalyze the production of ammonia from atmospheric nitrogen:


mathrm{N_2 + 8 H^+ + 8 e^- + 16 ATP + 16 H_2O longrightarrow 2 NH_3 + H_2 + 16 ADP + 16 P_i}
The biosynthesis of the FeMoco active site is highly complex.JOURNAL, A newly discovered role for iron-sulfur clusters, Patricia C., 10.1073/pnas.0805713105, PNAS, 2008, 105, 11589–11590, 18697949, Dos Santos, Dean, Dennis R., 33, 2575256, 2008PNAS..10511589D, File:FeMoco cluster.svg|thumb|right|180px|Structure of the FeMoco active site of nitrogenasenitrogenaseFile:Molybdenum cofactor.svg|thumb|alt=Skeletal structure of a molybdopterin with a single molybdenum atom bound to both of the thiolate groups|The molybdenum cofactor (pictured) is composed of a molybdenum-free organic complex called molybdopterinmolybdopterinMolybdate is transported in the body as MoO42−.WEB, Mitchell, Phillip C. H., Overview of Environment Database, International Molybdenum Association, 2003,weblinkweblink" title="web.archive.org/web/20071018005253weblink">weblink 2007-10-18, 2007-05-05,

Human metabolism and deficiency

Molybdenum is an essential trace dietary element.BOOK, Guenter, Schwarz, Abdel A., Belaidi, Astrid Sigel, Helmut Sigel, Roland K. O. Sigel, Interrelations between Essential Metal Ions and Human Diseases, Metal Ions in Life Sciences, 13, 2013, Springer, 415–450, Chapter 13. Molybdenum in Human Health and Disease, 10.1007/978-94-007-7500-8_13, 24470099, 978-94-007-7499-5, Four mammalian Mo-dependent enzymes are known, all of them harboring a pterin-based molybdenum cofactor (Moco) in their active site: sulfite oxidase, xanthine oxidoreductase, aldehyde oxidase, and mitochondrial amidoxime reductase.JOURNAL, 10.1002/biof.55, Cell biology of molybdenum, 2009, Mendel, Ralf R., BioFactors, 35, 5, 429–34, 19623604, People severely deficient in molybdenum have poorly functioning sulfite oxidase and are prone to toxic reactions to sulfites in foods.Blaylock Wellness Report, February 2010, page 3.JOURNAL, 427300, Molecular Basis of the Biological Function of Molybdenum. The Relationship between Sulfite Oxidase and the Acute Toxicity of Bisulfite and SO2., 1973, Cohen, H. J., Drew, R. T., Johnson, J. L., Rajagopalan, K. V., 70, 12 Pt 1–2, 3655–3659, Proceedings of the National Academy of Sciences of the United States of America, 1973PNAS...70.3655C, 10.1073/pnas.70.12.3655, 4519654, The human body contains about 0.07 mg of molybdenum per kilogram of body weight,BOOK, 2001, Inorganic chemistry, Arnold F., Holleman, Egon, Wiberg, 1384,weblink Academic Press, 978-0-12-352651-9, with higher concentrations in the liver and kidneys and lower in the vertebrae. Molybdenum is also present within human tooth enamel and may help prevent its decay.JOURNAL, Environmental Effects of Molybdenum on Caries, M. E. J., Curzon, J., Kubota, B. G., Bibby, Journal of Dental Research, 50, 1, 1971, 74–77, 10.1177/00220345710500013401, Acute toxicity has not been seen in humans, and the toxicity depends strongly on the chemical state. Studies on rats show a median lethal dose (LD50) as low as 180 mg/kg for some Mo compounds.WEB,weblink Oak Ridge National Laboratory, Risk Assessment Information System: Toxicity Summary for Molybdenum, 2008-04-23,weblink" title="web.archive.org/web/20070919204536weblink">weblink September 19, 2007, Although human toxicity data is unavailable, animal studies have shown that chronic ingestion of more than 10 mg/day of molybdenum can cause diarrhea, growth retardation, infertility, low birth weight, and gout; it can also affect the lungs, kidneys, and liver.JOURNAL, 10.1081/CLT-100102422, 231–237, Clinical Toxicology, 1999, 37, 2, Molybdenum, Donald G., Barceloux‌, Donald, Barceloux, 10382558, Sodium tungstate is a competitive inhibitor of molybdenum. Dietary tungsten reduces the concentration of molybdenum in tissues.Low soil concentration of molybdenum in a geographical band from northern China to Iran results in a general dietary molybdenum deficiency, and is associated with increased rates of esophageal cancer.JOURNAL, Cancer Research, 40, 1980, Research on Esophageal Cancer in China: a Review, Chung S., Yang,weblink 6992989, 8 Pt 1, 2633–44, 2011-12-30,weblink" title="web.archive.org/web/20151123134413weblink">weblink 2015-11-23, live, JOURNAL, Archives of Iranian Medicine, 2008, 11, 392, Nail Molybdenum and Zinc Contents in Populations with Low and Moderate Incidence of Esophageal Cancer, Mohsen, Nouri, 4, Chalian, Hamid, Bahman, Atiyeh, Mollahajian, Hamid, Ahmadi-Faghih, Mohammadamin, Fakheri, Hafez, Soroush, Ahmadreza,weblink 2009-03-23,weblink" title="web.archive.org/web/20110719080706weblink">weblink 2011-07-19, live, Compared to the United States, which has a greater supply of molybdenum in the soil, people living in those areas have about 16 times greater risk for esophageal squamous cell carcinoma.JOURNAL,weblink Cancer Research, 54, 2029s–2031s, 1994, Prevention of Esophageal Cancer: The Nutrition Intervention Trials in Linxian, China, Philip R., Taylor, Bing, Li, Sanford M., Dawsey, Jun-Yao, Li, Chung S., Yang, Wande, Guo, William J., Blot, 8137333, 7 Suppl, 2016-07-01,weblink" title="web.archive.org/web/20160917181412weblink">weblink 2016-09-17, live, Molybdenum deficiency has also been reported as a consequence of non-molybdenum supplemented total parenteral nutrition (complete intravenous feeding) for long periods of time. It results in high blood levels of sulfite and urate, in much the same way as molybdenum cofactor deficiency. However (presumably since pure molybdenum deficiency from this cause occurs primarily in adults), the neurological consequences are not as marked as in cases of congenital cofactor deficiency.JOURNAL, 1911702, 6426561, 1984, Abumrad, N. N., Molybdenum—is it an essential trace metal?, 60, 2, 163–71, Bulletin of the New York Academy of Medicine,

Related diseases

A congenital molybdenum cofactor deficiency disease, seen in infants, is an inability to synthesize molybdenum cofactor, the heterocyclic molecule discussed above that binds molybdenum at the active site in all known human enzymes that use molybdenum. The resulting deficiency results in high levels of sulfite and urate, and neurological damage.JOURNAL, Splice-specific Functions of Gephyrin in Molybdenum Cofactor Biosynthesis, Smolinsky, B, Journal of Biological Chemistry, 10.1074/jbc.M800985200, 2008, 283, 17370–9, 18411266, 25, Eichler, S. A., Buchmeier, S., Meier, J. C., Schwarz, G., JOURNAL, 10.1007/s004390051023, Genetics of molybdenum cofactor deficiency, 2000, Reiss, J., Human Genetics, 106, 157–63, 10746556, 2,

Copper-molybdenum antagonism

High levels of molybdenum can interfere with the body's uptake of copper, producing copper deficiency. Molybdenum prevents plasma proteins from binding to copper, and it also increases the amount of copper that is excreted in urine. Ruminants that consume high levels of molybdenum suffer from diarrhea, stunted growth, anemia, and achromotrichia (loss of fur pigment). These symptoms can be alleviated by copper supplements, either dietary and injection.JOURNAL, Suttle, N. F., Recent studies of the copper-molybdenum antagonism, Proceedings of the Nutrition Society, 33, 3, 299–305, 1974, 10.1079/PNS19740053, 4617883, The effective copper deficiency can be aggravated by excess sulfur.Hauer, Gerald Copper deficiency in cattle {{Webarchive|url=https://web.archive.org/web/20110910172605weblink |date=2011-09-10 }}. Bison Producers of Alberta. Accessed Dec. 16, 2010.Copper reduction or deficiency can also be deliberately induced for therapeutic purposes by the compound ammonium tetrathiomolybdate, in which the bright red anion tetrathiomolybdate is the copper-chelating agent. Tetrathiomolybdate was first used therapeutically in the treatment of copper toxicosis in animals. It was then introduced as a treatment in Wilson's disease, a hereditary copper metabolism disorder in humans; it acts both by competing with copper absorption in the bowel and by increasing excretion. It has also been found to have an inhibitory effect on angiogenesis, potentially by inhibiting the membrane translocation process that is dependent on copper ions.JOURNAL, Nickel, W, The Mystery of nonclassical protein secretion, a current view on cargo proteins and potential export routes, Eur. J. Biochem., 2003, 270, 2109–2119, 10.1046/j.1432-1033.2003.03577.x, 12752430, 10, This is a promising avenue for investigation of treatments for cancer, age-related macular degeneration, and other diseases that involve a pathologic proliferation of blood vessels.JOURNAL, Brewer GJ, Treatment of Wilson disease with ammonium tetrathiomolybdate: III. Initial therapy in a total of 55 neurologically affected patients and follow-up with zinc therapy, Arch Neurol, 2003, 60, 3, 379–85, 12633149, 10.1001/archneur.60.3.379, Hedera, P., Kluin, K. J., Carlson, M., Askari, F., Dick, R. B., Sitterly, J., Fink, J. K., JOURNAL, 10656425, 2000, Brewer, G. J., Dick, R. D., Grover, D. K., Leclaire, V., Tseng, M., Wicha, M., Pienta, K., Redman, B. G., Jahan, T., Sondak, V. K., Strawderman, M., LeCarpentier, G., Merajver, S. D., Treatment of metastatic cancer with tetrathiomolybdate, an anticopper, antiangiogenic agent: Phase I study, 6, 1, 1–10, Clinical Cancer Research,

Dietary recommendations

In 2000, the then U.S. Institute of Medicine (now the National Academy of Medicine, NAM) updated its Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for molybdenum. If there is not sufficient information to establish EARs and RDAs, an estimate designated Adequate Intake (AI) is used instead.An AI of 2 micrograms (μg) of molybdenum per day was established for infants up to 6 months of age, and 3 Î¼g/day from 7 to 12 months of age, both for males and females. For older children and adults, the following daily RDAs have been established for molybdenum: 17 Î¼g from 1 to 3 years of age, 22 Î¼g from 4 to 8 years, 34 Î¼g from 9 to 13 years, 43 Î¼g from 14 to 18 years, and 45 Î¼g for persons 19 years old and older. All these RDAs are valid for both sexes. Pregnant or lactating females from 14 to 50 years of age have a higher daily RDA of 50 Î¼g of molybdenum.As for safety, the NAM sets tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. In the case of molybdenum, the UL is 2000 Î¼g/day. Collectively the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs).BOOK, Institute of Medicine, Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc, Molybdenum, The National Academies Press, 2000, Washington, DC, 420–441,weblink The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. AI and UL defined the same as in United States. For women and men ages 15 and older the AI is set at 65 Î¼g/day. Pregnant and lactating women have the same AI. For children aged 1–14 years, the AIs increase with age from 15 to 45 Î¼g/day. The adult AIs are higher than the U.S. RDAs,WEB, Overview on Dietary Reference Values for the EU population as derived by the EFSA Panel on Dietetic Products, Nutrition and Allergies, 2017,weblink 2017-09-10,weblink 2017-08-28, live, but on the other hand, the European Food Safety Authority reviewed the same safety question and set its UL at 600 Î¼g/day, which is much lower than the U.S. value.{{citation| title = Tolerable Upper Intake Levels For Vitamins And Minerals| publisher = European Food Safety Authority| year = 2006| url =weblink| access-date = 2017-09-10| archive-url =weblink" title="web.archive.org/web/20160316225123weblink">weblink| archive-date = 2016-03-16| url-status = live}}For U.S. food and dietary supplement labeling purposes, the amount in a serving is expressed as a percent of Daily Value (%DV). For molybdenum labeling purposes 100% of the Daily Value was 75 Î¼g, but as of May 27, 2016 it was revised to 45 Î¼g.WEB,weblink Federal Register May 27, 2016 Food Labeling: Revision of the Nutrition and Supplement Facts Labels. FR page 33982., September 10, 2017,weblink August 8, 2016, live, A table of the old and new adult Daily Values is provided at Reference Daily Intake. The original deadline to be in compliance was July 28, 2018, but on September 29, 2017 the Food and Drug Administration (FDA) released a proposed rule that extended the deadline to January 1, 2020 for large companies and January 1, 2021 for small companies.WEB,weblink "Changes to the Nutrition Facts Panel - Compliance Date", 2017-10-24,weblink 2017-03-12, live,

Food sources

Average daily intake varies between 120 and 240 μg/day, which is higher than dietary recommendations.JOURNAL, 10.1007/BF01811327, The role of molybdenum in human biology, 1983, Coughlan, M. P., Journal of Inherited Metabolic Disease, 6, 70–77, 6312191, S1, Pork, lamb, and beef liver each have approximately 1.5 parts per million of molybdenum. Other significant dietary sources include green beans, eggs, sunflower seeds, wheat flour, lentils, cucumbers, and cereal grain.

Precautions

Molybdenum dusts and fumes, generated by mining or metalworking, can be toxic, especially if ingested (including dust trapped in the sinuses and later swallowed). Low levels of prolonged exposure can cause irritation to the eyes and skin. Direct inhalation or ingestion of molybdenum and its oxides should be avoided.WEB, Material Safety Data Sheet – Molybdenum, The REMBAR Company, Inc., 2000-09-19,weblink 2007-05-13,weblink" title="web.archive.org/web/20070323103727weblink">weblink March 23, 2007, WEB, Material Safety Data Sheet – Molybdenum Powder, CERAC, Inc., 1994-02-23,weblinkweblink" title="web.archive.org/web/20110708132733weblink">weblink 2011-07-08, 2007-10-19, OSHA regulations specify the maximum permissible molybdenum exposure in an 8-hour day as 5 mg/m3. Chronic exposure to 60 to 600 mg/m3 can cause symptoms including fatigue, headaches and joint pains.WEB, NIOSH Documentation for ILDHs Molybdenum, National Institute for Occupational Safety and Health, 1996-08-16,weblink 2007-05-31,weblink" title="web.archive.org/web/20070807130614weblink">weblink 2007-08-07, live, At levels of 5000 mg/m3, molybdenum is immediately dangerous to life and health.WEB, CDC – NIOSH Pocket Guide to Chemical Hazards – Molybdenum,weblink www.cdc.gov, 2015-11-20,weblink" title="web.archive.org/web/20151120130010weblink">weblink 2015-11-20, live,

See also

References

{{Reflist|30em}}

Bibliography

  • BOOK, Lettera di Giulio Candida al signor Vincenzo Petagna - Sulla formazione del molibdeno, 1785, Naples, Giuseppe Maria Porcelli,weblink gcandida-molibdeno,

External links

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