Vanadium (V)
Vanadium (V) is a metallic element with the atomic number 23 and is characterized by its shiny appearance and malleability, though it becomes brittle in the presence of impurities. It is primarily utilized in the production of ferrovanadium, an alloy that enhances the toughness, wear resistance, and thermal stability of steel, which accounts for about 92% of its consumption in the United States. Vanadium is commonly found in minerals such as patronite and vanadinite and is sourced from regions including the United States, China, Russia, and South Africa. Historically, vanadium was first identified in the early 19th century and has since been processed to obtain pure metal through various chemical methods.
In addition to steelmaking, vanadium has applications in aerospace and nuclear industries due to its strength and corrosion resistance. It also plays a role in catalysis, particularly in the production of sulfuric acid and certain synthetic rubbers. Though vanadium may serve as an essential trace mineral and is found in some dietary supplements, its health effects are still being researched, especially concerning its potential benefits in diabetes management and cancer treatment. Health risks associated with vanadium primarily arise from industrial exposure, which can lead to respiratory and eye irritation. This multifaceted element continues to attract interest across scientific and industrial fields.
Vanadium (V)
Where Found
Vanadium minerals are found in the United States in Arkansas, Colorado, Idaho, and Utah. Major international sources are China, Russia, and South Africa. Vanadium is usually associated with igneous rocks and often with other metals, such as lead, iron, chromium, and uranium.
Primary Uses
Vanadium combined with iron, called ferrovanadium, is used in making special steels valued for their toughness, resistance to wear, and stability at high temperatures. Approximately 92 percent of U.S. consumption of vanadium is for alloying iron and steel, with the balance used in catalysts for chemical production.
Technical Definition
Vanadium (atomic number 23, chemical symbol V) is a shiny metallic element with a density of 6 kilograms per liter (less than iron) that melts at 2,188 kelvin (higher than iron). It is malleable when pure but becomes brittle in the presence of impurities, particularly carbon. It is stable in air at room temperature but oxidizes above 920 kelvin. There are isotopes of mass numbers 50 and 51 (V50 and V51) of which the former is weakly radioactive.
Description, Distribution, and Forms
Vanadium occurs in the Earth’s crust at an average concentration of 136 parts per million; it is the nineteenth most abundant element. Vanadium minerals include patronite (VS4), vanadinite (Pb5 [VO4]3Cl), carnotite (K[UO2][VO4]), and more than sixty others. Vanadates are sometimes found in phosphate rock or titaniferous magnetite. Small amounts of vanadium occur in petroleum, oil sands, oil shale, coal, and meteorites. Certain sea creatures, such as sea squirts (ascidians), accumulate vanadium from seawater, attaining concentrations ten million times higher in their blood than are in the water. Low levels of vanadium are found in most plant and animal tissues, where its function is not always clear. The average human body contains about 1 milligram of vanadium.
History
Vanadium was first noticed by Andrés Manuel del Rio (1787-1849) in 1801 in Mexico. Del Rio found evidence of an element he called erythronium in a lead ore (probably what would today be recognized as vanadinite). He later retracted his discovery based on consulting with chemists in France. In 1830, Nils Gabriel Sefström (1787-1895), a student of Jöns Jacob Berzelius (1779-1848), working in Sweden, isolated material from iron-making slag that he realized was the same as the erythronium reported by Del Rio. He named the element vanadium after the Nordic goddess Vanadis. Neither Sefström nor Del Rio succeeded in isolating the pure metal. Berzelius was the first to describe the element’s properties in detail. Approximately 70 percent pure metallic vanadium was prepared by Henry E. Roscoe (1833-1915) in 1867, but purity approaching 100 percent was not achieved until the twentieth century.
Obtaining Vanadium
Preliminary treatment of ores involves crushing, pulverizing, and sifting, followed by flotation procedures to eliminate unwanted silicates. The ore concentrates are then roasted in air with sodium carbonate to yield sodium metavanadate. The latter is converted to vanadium pentoxide (V2O5) by acidification, using sulfuric acid followed by strong heating. Vanadium pentoxide is the starting material for preparation of other vanadium compounds, or of the metal itself. Heating the pentoxide to high temperature (1,223 kelvin) with calcium in the absence of air yields metallic vanadium. The metal may also be obtained by reaction of trichloride with magnesium or (in small amounts with high purity) by thermal decomposition of the triiodide. Ferrovanadium for steelmaking contains about 50 percent vanadium and is made by heating the pentoxide with ferrosilicon and lime in an electric furnace. The lime combines with the silicon to form slag.
The United States imports 76 percent of its ferrovanadium from the Czech Republic. Most of the U.S. production of vanadium is from slag, petroleum combustion residues, fly ash, or recycled catalysts. Carnotite, when processed for its uranium content, yields vanadium as a by-product, but mining of other vanadium minerals is uneconomical in the United States.
Uses of Vanadium
Vanadium is used in alloys for aircraft and for nuclear applications. Vanadium compounds are also used in ceramics and as catalysts in the production of maleic anhydride and sulfuric acid.
Pure elemental vanadium is too expensive for any but the most critical applications. One is the use of vanadium foil on steel to which titanium is to be bonded. Pure vanadium is also used to make a superconducting alloy with gallium (V3Ga) for use in electromagnets. This substance becomes superconducting below 15 kelvin.
Larger amounts of vanadium are used in special steels. In these cases, the starting material is ferrovanadium, which may contain up to 80 percent vanadium (lower grades are available). Tool steels containing vanadium, iron, and chromium are used for socket wrenches, pliers, and knife blades. Vanadium content of tool steels can be as high as 4 percent. Smaller amounts of vanadium (a few tenths of a percent) are added to many steels to combine with carbon and nitrogen and improve grain size. Some of the beneficial effects of vanadium in steel result from vanadium carbides, which may form spontaneously from the carbon in steel or may be added as such. Vanadium carbides are produced by heating sodium metavanadate with carbon in a vacuum furnace.
Vanadium steel finds application in automobile parts such as axles, transmission parts, and springs, where it is valued for its light weight, toughness, and resistance to wear. The famous Model-T Ford of the early twentieth century was advertised to contain vanadium steel parts. In the military, vanadium steel is used for armor and for soldiers’ helmets.
In vanadium alloys, corrosion resistance combined with strength is important for the pipes and tubes used in boilers and chemical plants. In nuclear reactors, not only corrosion resistance but also the low cross section of vanadium for the capture of thermal neutrons is favorable. An example is an alloy of 80 percent vanadium, 15 percent chromium, and 5 percent titanium, which is suitable for fast breeder reactors using liquid sodium potassium alloy as coolant.
Vanadium is also used in nonferrous materials, particularly aluminum and titanium alloys. An alloy of 90 percent titanium, 4 percent aluminum, and 6 percent vanadium is as strong as but lighter than steel and suitable for use in aircraft.
Vanadium compounds are used in catalytic applications. Probably the most important of these is in the contact process for sulfuric acid manufacture, where vanadium pentoxide is used to catalyze the reaction of oxygen with sulfur dioxide. oxidation reactions catalyzed by vanadium pentoxide include the oxidation of naphthalene to phthalic anhydride and of butene to maleic anhydride. Vanadium compounds such as vanadium trichloride and vanadium oxytrichloride are components, along with organoaluminum compounds, of catalyst systems for manufacturing various polyolefins, including ethylene propylene diene type M (EDPM) synthetic rubber. This product has superior properties for automotive gaskets and hoses and membranes under the shingles of the roof of a building.
Other applications of vanadium compounds include the use of vanadium salts to catalyze the oxidation of aniline in manufacture of the dyestuff aniline black and the use of vanadium pentoxide as a mordant in dyeing. Small amounts of vanadium pentoxide are used in ceramic glazes and as an additive in glass to reduce transmission of ultraviolet light. There is interest in silver vanadium oxide as a cathode material in lithium batteries with high energy densities.
Vanadium may be an essential trace mineral in nutrition and is an ingredient of vitamin and mineral supplements. There is some evidence that vanadium compounds are helpful in potentiating the effect of insulin in the treatment of diabetes, but no specific treatment has received government approval. Vanadium compounds have also been shown to kill cancer cells, but again, no approved treatment is available.
There are health issues relating to vanadium. Industrial exposure to vanadium-containing dust is a health hazard that may be encountered in milling or machining of vanadium alloys or in handling vanadium chemicals such as vanadium pentoxide. Fly ash from combustion of coal and soot from combustion of heavy oil are sources of vanadium in the environment. Eye and lung irritation and other problems can result from exposure.
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