Vanadium, In, Atomic number 23

General

Vanadium, veraltet auch Vanadium, is a chemical element with the symbol V and atomic number 23. It is a steel-gray, bluish shimmering, In the pure state very soft transition metal. The metal in the periodic table, together with the heavier niobium, Tantalum and Dubnium the 5. Gruppe oder Vanadiumgruppe. Most of the vanadium is used as a so-called ferro-vanadium in the steel-making. The addition of vanadium to chromium-vanadium steel leads to an increase in toughness and therefore a higher resistance of the steel.

The element has different biological meanings and is essential for many living things. It plays a role in the control of the phosphorylation enzymes and is used by bacteria to nitrogen fixation.

The bekannteste Verbindung Vanadiums ist des Vanadium(In)-oxide, which is used as a catalyst for the production of sulfuric acid.

For the first time later vanadium 1801 by the Spanish mineralogist Andres Manuel del Rio, a Mexican lead ore, dem späteren Vanadinit, discovered. He named the new element first because of the variegation of the compounds Panchromium, later Erythronium, as the red-colored salts on acidification. The discovery del Rio, but recanted shortly thereafter, as first Alexander von Humboldt and later the French chemist HV. Collett-Desotils claimed on the basis of similarity to chromium compounds, with the new element would be contaminated by chromium.

The rediscovery of the element managed 1830 the Swedish chemist Nils Gabriel Sefström. He examined iron from the Swedish iron ore mine Taberg, by solving this in hydrochloric acid. He discovered, among other substances known to an unknown element, that in some properties of the chromium, similar in other uranium, but after further investigation, none of these elements. The new element he named after Vanadis, an epithet of the Nordic deity Freyja. A short time later, Friedrich Wöhler provided, who had been engaged in the task of Berzelius, the identity of vanadium with Erythronium.

Metallic vanadium was first 1867 Henry Enfield Roscoe by reduction of vanadium(II)-with hydrogen chloride. 99,7 % pure vanadium could 1925John Wesley Marden and Malcolm Rich for the first time by reduction of vanadium(In)-calcium oxide with win.

Vanadium was first 1903 used, as in England, the first vanadium-containing steel was produced. The increased use of the element in the steel industry began 1905, began as Henry Ford Vanadium steel for the construction of automobiles.

Occurrence

Vanadium is a common element on Earth, its share of the continental crust is about 120 ppm. A similar frequency element zirconium have, Chlorine and chromium. The element is not dignified, but only bound in various minerals ago. Despite the frequency of vanadium are deposits with high concentrations of the element rarely, many vanadium minerals do not occur frequently. Compared to the Earth's crust is much lower content in sea water, it is about 1,3 μg/l.

Zu den wichtigsten Vanadiummineralen ZAHLEN vor allem Vanadate who Vanadinit [Pb5(VO4)3Cl], Descloizit Pb(Zn, With) [OH|VO4] und Carnotit [K2(UO2)2(VO4)2·3H2The], sowie das Vanadiumsulfid Patronit VS4. Most of the vanadium is found in trace amounts in other minerals, especially iron ores such as magnetite. The vanadium content of titanium-magnetite ores is usually between 0,3 and 0,8 %, but can in some South African ores to 1,7 % reach.

Animals and plants contain vanadium, so man contains about 0,3 mg / kg des elementes. This is usually located in cell nuclei or mitochondria. Some living things, especially some Seescheidenarten and the fly agaric, are capable of, Vanadium enrichment. In ascidians, the vanadium content up to 107 times as large as in the surrounding sea water. Based on the vanadium content of living organisms are also coal and petroleum, arising from these, vanadiumhaltig. The content is up to 0,1 %. Particularly high levels of vanadium are found in oil from Venezuela and Canada.

Förderung an Vanadiumerz

In 2006 total 55.700 Tons Vanadiumerz gefördert (gerechnet as Vanadiummetall). The main producing countries are South Africa, China und Russland. Vanadium is not a scarce resource, There are a total reserves of 63 Known million tons.

Extraction and representation

The representation of vanadium proceeds in several steps. First you have from different source materials vanadium(In)-oxide are obtained. This can then be reduced to elemental metal and clean if necessary.

Possible precursors, from which vanadium can be obtained, Vanadiumerze who oder sind Carnotit Patronit, vanadium-containing titanium-magnetite ores and petroleum. Vanadium ores were important in earlier times for the production, play no important role, and more especially of the titanium-magnetite ores have been replaced.

If vanadium-containing ores reduced in the blast furnace process to iron, the vanadium remains first in the pig iron. To further processing the pig iron to steel, is injected during desFrischens oxygen. In this case, the vanadium is transferred to the slag. This contains up to 25 % Vanadium(In)-oxide and is the main source of extracting the metal. To the pure vanadium(In)-to obtain oxide, the finely ground slag roasted oxidizing with sodium salts such as sodium chloride or sodium carbonate. It is water-soluble sodium metavanadate forms, the rest of the slag is separated by leaching. By addition of acid and the resulting ammonium salts from the solution precipitated unlöslicheAmmoniumpolyvanadat. This can by roasting to vanadium(In)-oxide is converted. There are other vanadium-bearing ores in an identical way, the oxide can be obtained. Petroleum the vanadium can be extracted by forming an emulsion with the addition of water and magnesium nitrate. The further work is done as for the extraction of iron ore.

The actual extraction of vanadium by reduction of vanadium(In)-oxids mit others Metallen. Suitable reducing agents are aluminum, Calcium, Be ferro-silicon or carbon Uses; However, with the latter formed during the reaction Carbide, which may be separated from the heavy metal.

\mathrm{V_2O_5 + 5\ Ca \longrightarrow 2\ V + 5\ CaO}Reduction with calcium

In order to obtain pure vanadium, expensive calcium or aluminum is used as the reducing agent, to achieve because of the cheaper high purity ferrosilicon is no. While calcium is extracted directly with pure vanadium, is formed with aluminum initially a vanadium-aluminum alloy, is obtained from the sublimation of pure vanadium in vacuo.

A large part of the vanadium is not as pure metal, but in the form of the iron-vanadium alloy Ferrovanadium, at least 50 % Containing vanadium, used. To make this, it is not necessary, to win before the pure vanadium. Instead, the vanadium- reduced and ferrous slag with ferrosilicon and lime to ferrovanadium. This alloy is sufficient for most technical applications.

Pure vanadium can be either electrochemically or represented by the Van Arkel-de Boer process. For this purpose, the pure vanadium is melted together with iodine in an evacuated glass ampoule. The vanadium formed in the heated ampoule(III)-iodide decomposes on a hot tungsten wire to high-purity vanadium and iodine.

\mathrm{2\ V + 3\ I_2 \rightleftharpoons 2\ VI_3}Reaction in the Van Arkel-de Boer method

Properties

Physical Properties

Kristallstruktur von Vanadium, a = 302,4 pm

Vanadium is a non-magnetic, tough, malleable and clear steel blue heavy metal with a density of 6,11 g/cm3. Pure vanadium is relatively soft, but is harder by admixtures of other elements and then has a high mechanical strength. In most properties, it resembles its neighbors in the periodic table, dem Titan. The melting point of pure vanadium is 1910 ° C, this is, however, significantly increased by impurities such as carbon. With a content of 10 % Carbon he is about 2700 ° C. Vanadium crystallizes as chromium or niobium in a body-centered cubic space group Kristallstrukturmit Im\bar{3}m und them Lattice parameter a = 302,4 pm and two formula units per unit cell.

Below a critical temperature of 5,13 K is for vanadium superconductor. Just as pure vanadium are also alloys of vanadium with gallium, Niobium and zirconium superconducting. At temperatures below 5,13 K zeigt Vanadium, as well as vanadium, niobium and tantalum group metals, in small clumps to 200 Atoms have not been declared, spontane elektrische Polarisation, otherwise possessed only non-metallic materials.

Chemical Properties

Vanadium is a base metal and capable of, to react with many non-metals. In air, it stays for weeks metallic luster. When looking at long periods is clearly visible green rust perceived. Vanadium should remain preserved, it must be kept under argon. In the heat it is attacked by oxygen and vanadium(In)-oxid oxidiert. While carbon and nitrogen react with vanadium only at white heat, is the reaction with fluorine and chlorine in the cold instead of.

To acids and bases, vanadium is the most stable at room temperature because of a thin, passivating oxide layer, attacked it is only by hydrofluoric acid, and strongly oxidizing acids such as hot nitric acid, concentrated sulfuric acid and aqua regia.

Up to a temperature of 500 Vanadium ° C ist in der Lage, To absorb hydrogen. Here, the metal is brittle and powders can be easily. Removal can be in the hydrogen 700 ° C im Vakuum.

Isotope

Of vanadium total 25 Isotopes and other 6 Kernisomere known. Of these, two are naturally occurring. These are the isotopes 50V has a natural abundance of 0,25 % and 51V with a frequency of 99,75 %. 50V is weakly radioactive, it decays with a Halbwertszeitvon 1,5 · 1017 Years 83 % under electron capture 50You, to 17 % under β-Decay to 50Cr. Both cores may be used for imaging by NMR spectroscopy.

The most stable artificial isotopes are 48V with a half-life of 16 Days and 49V with a half-life of 330 Meet. These find use as a tracer. All other isotopes and Kernisomere are very unstable and decay in minutes or seconds.

Use

Pure vanadium is used, only a small percentage because of its low neutron capture cross section as a cladding material for nuclear fuel.[23] However, it is also more stable vanadium alloys are used. About 90 % the production in a variety of alloys, most of the metals iron, Titan, Nickel, Chrome, Aluminum or manganese used. Only a small part in compounds, meist as Vanadium(In)-oxide used.

With 85 % of vanadium produced is by far the largest part consumed in the steel industry. Since no high purities are required, ferrovanadium is used as raw material. Vanadium increases even in small quantities in steel dieFestigkeit and toughness, and thus the wear resistance significantly. This is caused by the formation of hard vanadium. Depending on the application, different amounts of added vanadium. To contain structural steels undWerkzeugstähle only small amounts (0,2 to 0,5 %) Vanadium, Speed ​​steel up to 5 %. Vanadium steels are used primarily for mechanically stressed tools and springs. Steels, containing in addition to iron and cobalt and vanadium, are magnetically.

Titanium alloys, the vanadium and aluminum usually contain, are particularly stable and heat resistant and are used in aircraft for structural parts and turbine blades of aircraft engines.

Vanadium is used in a type of so-called redox flow cell as the main electrolyte, an example of such an application is the vanadium redox battery.

Proof

A laboratory test provides the microcosmic salt bead, characteristic appears green when the vanadium in the reducing flame. The oxidizing flame is pale yellow and so too unspecific.

A qualitative test for vanadium based on the formation of Peroxovanadiumionen. For this purpose, an acidic solution, the vanadium in the oxidation state +5 contains, mixed with a little hydrogen peroxide. It is the reddish-brown [In(The2)]3+-cation. This reacts with larger amounts of hydrogen peroxide to pale yellow Peroxovanadiumsäure H3[VO2(The2)2].

Quantitatively, vanadium can be determined by titration. To a vanadium-containing sulfuric acid solution is oxidized with potassium permanganate to pentavalent vanadium with an iron, and then(II)-sulfate solution and back-titrated diphenylamine alsIndikator. Also a reduction of the present pentavalent vanadium with iron(II)-sulphate for the oxidation state and subsequent potentiometric titration with potassium permanganate solution is possible.

In the modern laboratory can be detected vanadium with several methods. These are for example the atomic absorption spectrometry at 318,5 nm and spectrophotometry with N-benzoyl-N--phenylhydroxylamine as color reagent at 546 nm.

Biological significance

Vanadium compounds have different biological meanings. Characteristic of vanadium is, that both anionic as vanadate, as well as cationically VO2+, VO2+ or V3+ occurs. Vanadates have great similarity zuPhosphaten and therefore have similar effects. Since vanadate binds more strongly to enzymes suitable as phosphate, It is capable of, To block the phosphorylation of enzymes and control so. This concerns for example the sodium-potassium ATPase, the transport of sodium and potassium controls in cells. This blocking can with desferrioxamine B, which forms a stable complex with vanadate, be removed quickly. Furthermore, vanadium affects dieGlucoseaufnahme. It is capable of, in the liver to stimulate glycolysis and inhibit the competitive process of gluconeogenesis. This leads to a reduction of the glucose level in the blood. Therefore, it is studied, if vanadium compounds for the treatment of diabetes mellitus type 2 suitable are. However, there are still no clear results have been found. In addition, vanadium stimulates the oxidation of phospholipids and suppresses the synthesis of cholesterol by inhibiting squalene synthase, a microsomal enzyme system of liver. Consequently caused a lack elevated levels of cholesterol and triglycerides in the blood plasma.

In plants, vanadium plays a role in photosynthesis. It is capable of, to catalyze the reaction to form 5-aminolevulinic acid without enzyme. This is an important precursor for the production of chlorophyll.

In some organisms are present vanadium-containing enzymes, so have some types of bacteria for nitrogen fixation vanadium-containing nitrogenase. Examples of these are species of the genus Azotobacter and the cyanobacterium Anabaenavariabilis. However, these nitrogenases are not as powerful as the more common molybdenum nitrogenase and are therefore activated only when molybdenum deficiency. More vanadium-containing enzymes can be found in brown algae and lichens. These have vanadium-containing haloperoxidases, with which they chloro-, Brom- build or iodine organic compounds.

The function of the in large quantities in sea squirts present as metalloproteins Vanabine vanadium is not yet known. Originally it was assumed, that the vanadium is similar to hemoglobin than oxygen transporter; However, this has proven to be wrong.

Hazards

Like other metal dust is also flammable dust vanadium. Vanadium and its inorganic compounds have been found to be carcinogenic in animal experiments. They are therefore in carcinogenicity category 2 classified. If vanadium dust inhaled by workers in derMetallverhüttung about for a long time, can it come to so-called Vanadismus. This recognized occupational disease may be in mucous membrane irritation, green black discoloration of the tongue, and chronic bronchial, Lungs- and intestinal diseases express.

Connections

Vanadium compounds may be present in various oxidation states. Often, the steps +5, +4, +3 and +2, seltener sind 1, 0, -1 And -3. The most important and most stable oxidation states are 5 und 4. +1, 0, -1 And -3. The most important and most stable oxidation states are +5 and +4.

Aqueous solution

In aqueous solution, vanadium can be easily converted to various oxidation states. Since vanadium ions have various characteristic colors, It is here to change color.

In acidic solution pentavalent vanadium forms colorless VO2+-Ion, the first in the reduction of blue tetravalent VO2+-Ions are. The trivalent stage with V3+-Ion is green, the deepest, in aqueous solution achievable level, the divalent V2+-Ion is gray purple.

Oxygen compounds

The most important and most stable vanadium-oxygen compound is vanadium(In)-oxid V2The5. This orange colored compound is used in large quantities as a catalyst for the production of sulfuric acid. It acts as an oxygen carrier and during the reaction to another vanadium oxide, dem Vanadium(IV)-oxid VO2 reduced. Other well-known vanadium oxides are vanadium(III)-oxid V2The3 Vanadium und(II)-oxid VO.

In alkaline solution, forming vanadium(In)-Oxid Old Date, Salts with the anion VO43−. In contrast to the analogous phosphates, however, the vanadate ion is the most stable form; Hydrogen- Dihydrogenvanadate and vanadium as well as the free acid is unstable and is known only in dilute aqueous solutions. Acidified vanadate solutions are basic, form instead of the Hydrogenvanadate Polyvanadates, agglomerate in which up to ten vanadate. Vanadates are found in various minerals, Examples are Vanadinit, Descloizit und Carnot.

Halogen compounds

With the halogens fluorine, Chlorine, Bromine and iodine forms a variety of vanadium compounds. In the oxidation state +5 is only one connection, das Vanadium(In)-fluoride-known. In the oxidation states +4, +3 and +2 There are connections with all the halogens, only with iodine compounds are only in the stages +2 and +3 known. Of these halides the chlorides are, however, only vanadium(IV)-chlorid und Vanadium(III)-chlorid technically relevant. They serve as a catalyst for the production of ethylene-propylene-diene rubber.

Vanadiumoxidchloride

Vanadium is also mixed salts with oxygen and chlorine, the so-called Vanadiumoxidchloride. Vanadium(III)-oxidchlorid, VOCl, is a yellow-brown, water-soluble powder. The vanadium used in photography and as a textile mordant(IV)-oxidchlorid, VOCl2 consists of green, hygroscopic crystal panels, which dissolve in water with blue color. Vanadium(In)-oxidchlorid, VOCl3 Finally, a yellow liquid, which is very easily hydrolyzed by water. VOCl3 serves as a catalyst component in the Niederdruckethenpolymerisation.

Other vanadium compounds

In organic vanadium compounds vanadium reached its lowest oxidation states 0, -I and-III. Here are mainly the metallocenes, that sogenannten Vanadocene, important. These are used as a catalyst for polymerization of alkynes.

Vanadium carbide VC or in powder form, inter alia, for plasma spraying. Used plasma-arc welding. Furthermore, vanadium carbides is added, To reduce the grain growth. Are formed here the so-called cermets, which are particularly hard and wear resistant.

General
Name, Symbol,Atomic number Vanadium, In, 23
Series Transition metals
group, Period, Block 5, 4, d
Appearance steel gray metallic, bluish shimmer
CAS-Nummer 7440-62-2
Mass fraction of derErdhülle 0,041 %
Atomic
Atomic mass 50,9415 you
Atomradius (calculated) 135 (171) pm
Kovalenter Radius 153 pm
Electron configuration [It] 3d3 4s2
1. Ionization 650,9 kJ / mol
2. Ionization 1414 kJ / mol
3. Ionization 2830 kJ / mol
4. Ionization 4507 kJ / mol
5. Ionization 6298,7 kJ / mol
Physically
Physical State fixed
Crystal structure body centered cubic
Density 6,11 g/cm3 (20 ° C)
Mohs 7,0
Magnetism paramagnetisch (\chi_{m} = 3,8 · 10−4)
Melting point 2183 K (1910 ° C)
Boiling point 3680 K (3407 ° C)
Molar Volume 8,32 · 10−6 m3/mol
Heat of vaporization 453 kJ / mol
Schmelzwärme 21,5[5] kJ / mol
Speed ​​of sound 4560 m / s at 293,15 K
Specific heat capacity 489 J/(kg · K)
Electrical conductivity 5 · 106 A/(In · m)
Thermal conductivity 31 W /(m · K)
Chemical
Oxidation states +5, +4 ,+3 ,+2
Electronegativity 1,63 (Pauling-Scale)
Isotope
Isotope NH t1/2 ZA ZE (MeV) ZP
48In {a son.} 15,9735 d e 4,012 48You
49In {a son.} 330 d e 0,602 49You
50In 0,25 % 1,5 · 1017 a e 2,208 50You
b 1,037 50Cr
51In 99,75 % Stable
Safety
GHS Hazard Identification
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H- and P-SätzeH: no H-setsEUH: no EUH setsP: no P-sets Hazardous Materials IdentificationPowder

Leichtentzündlich Reizend
Slightly-
flammable
Lovely
(F) (Xi)

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