Saturday, December 3, 2011

vanadium chemical element

Vanadium a chemical element with the symbol V and atomic number 23 It
is a steel-gray, bluish shimmering, very soft in its pure state
transition metal. The metal in the periodic table, together with the
heavier niobium, tantalum, and the fifth dubnium Group or vanadium
group. The majority of vanadium is used as ferrovanadium called in
steel production. The addition of vanadium in chromium-vanadium steels
leads to an increase in toughness and thus to an increased resistance
of the steel.
The element has different biological meanings, and is essential for
many organisms. It plays a role in controlling the phosphorylation of
enzymes and is used by bacteria for nitrogen fixation.
The most popular combination of vanadium, vanadium (V) oxide, which is
used as a catalyst for the production of sulfuric acid.
Vanadium is a common element on earth, its share of the continental
crust is about 120 ppm. Have a similar frequency element zirconium,
and chromium chloride. The element is not dignified, but only bound in
different minerals before. Despite the frequency of the vanadium
deposits with high concentrations of the element are rare, many
vanadium minerals are not common. Compared to the Earth's crust, the
content in seawater is much lower, it lies at about 1.3 mg / l. [13]
Among the most important vanadium minerals are especially vanadates as
Vanadinite [Pb5 (VO4) 3Cl], descloizite Pb (Zn, Cu) [OH | VO4] and
carnotite [K2 (UO2) 2 (VO4) 2.3 H2O], and the vanadium sulfide
Patronit VS4. The majority of 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%
[14], but may reach in some South African ores up to 1.7% [12].
Animals and plants contain vanadium, man contains about 0.3 mg / kg of
the element. This is mostly found in cell nuclei or mitochondria. Some
living things, especially some Seescheidenarten and the fly agaric,
are able to accumulate vanadium. In ascidians, the vanadium content is
up to 107 times as large as in the surrounding sea water. [15] Based
on the vanadium content of organisms also are coal and petroleum,
which arise from these, vanadium. The content is up to 0.1%. [14]
Particularly high levels of vanadium are found in crude oil from
Venezuela and Canada. [16]
Vanadium ores to promote
In 2006, a total of 55 700 tonnes of Vanadium ores were promoted
(calculated as vanadium metal). The main producing countries are South
Africa, China and Russia. Vanadium is not a scarce resource, there are
a total of 63 million tonnes of known reserves. [17]
The presentation of vanadium takes place in several steps. First you
have from different source materials vanadium (V) oxide produced. This
can then be reduced to elemental metal and clean if necessary.
Possible starting materials from which vanadium can be recovered are
Vanadium ores such as carnotite or Patronit, vanadium-containing
titanium-magnetite ores and petroleum. Vanadium ores were important in
earlier times for the production, but they play no important role more
and have been replaced primarily by the titanium-magnetite ores.
Vanadium ores are reduced to iron in the blast furnace process, the
vanadium remains in the first pig iron. To continue to process the pig
iron into steel, is injected during refining oxygen. It goes over the
vanadium in the slag. This contains up to 25% vanadium (V) oxide and
is the main source for the extraction of the metal. To the pure
vanadium (V) oxide to win, the finely ground slag with sodium salts
such as sodium chloride or sodium carbonate is roasted oxidizing. This
forms water-soluble sodium metavanadate, which is separated from the
rest of the slag by leaching. The addition of acid and ammonium salts,
the resulting insoluble Ammoniumpolyvanadat falls out of solution.
This may be due to roasting of vanadium (V) oxide can be converted.
From other vanadium-bearing ores in an identical way, the oxide can be
obtained. From petroleum, the vanadium by forming an emulsion with the
addition of water and magnesium nitrate are extracted. The further
work is done as in the extraction of iron ore. [12]
The actual extraction of vanadium by reduction of vanadium (V) oxide
with other metals. As a reducing agent, aluminum, calcium, ferro
silicon and carbon are used, with the latter form, however, the
reaction carbides, which can be separated from the heavy metal.
Reduction with calcium
In order to obtain pure vanadium, expensive calcium or aluminum is
used as a reducing agent, as can be reached with the cheaper high
purity ferrosilicon no. While calcium is extracted directly with pure
vanadium, aluminum forms first a vanadium-aluminum alloy, is obtained
from the vacuum by sublimation in pure vanadium.
A large part of vanadium will not be used as a pure metal, but in the
form of iron-vanadium alloy, ferro vanadium, which contains at least
50% vanadium [12]. To produce them, it is not necessary to win before
the pure vanadium. Instead, the vanadium and iron-rich slag with lime
and ferro-silicon is reduced to ferrovanadium. This alloy is
sufficient for most engineering applications.
Pure vanadium can be displayed either electrochemically or by the Van
Arkel-de Boer method. To the pure vanadium is melted together with
iodine in an evacuated glass ampoule. The formed in the heated ampoule
vanadium (III) iodide decomposed on a hot tungsten filament to
high-purity vanadium, and iodine.

Physical Properties
Crystal structure of vanadium, a = 302.4 pm
Vanadium is a non-magnetic, ductile, malleable and clear steel blue
heavy metal with a density of 6.11 g/cm3. [12] Pure vanadium is
relatively soft, but harder by amounts of other elements and then has
a high mechanical strength. In most properties, it resembles its
neighbors in the periodic system, the Titan. The melting point of pure
vanadium is at 1910 ° C, this will be increased significantly by
impurities such as carbon. At a concentration of 10% carbon it is
about 2700 ° C. crystallized [16], vanadium, such as chromium or
niobium in a body-centered cubic crystal structure with space group
and lattice parameters a = 302.4 pm and two formula units per unit
cell. [18 ]
Below a critical temperature of 5.13 K becomes superconducting
vanadium. [19] Just as pure vanadium are also alloys of vanadium with
gallium, niobium and zirconium superconducting. At temperatures below
5.13 K shows vanadium, as well as the vanadium group metals niobium
and tantalum, in small lumps up to 200 atoms, a hitherto unexplained,
spontaneous electric polarization, as otherwise they have only
non-metallic substances. [20] [21]
Chemical Properties
Vanadium is a base metal and able to react with many non-metals. In
air, it stays for weeks metallic luster. When viewed over a long
period clearly visible green rust is perceived. Vanadium should be
preserved, it must be kept under argon. In the heat it is attacked by
oxygen and vanadium (V)-oxide. While carbon and nitrogen react with
vanadium only at white heat, the reaction takes place with fluorine
and chlorine in the cold.
Against acids and bases, vanadium is stable at room temperature is
usually attacked because of a thin passivating oxide layer, it is only
by hydrofluoric acid and strong oxidizing acids such as hot nitric
acid, concentrated sulfuric acid and aqua regia.
Up to a temperature of 500 ° C, vanadium is able to absorb hydrogen.
Here, the metal is brittle and can easily powders. Can remove the
hydrogen at 700 ° C in vacuum. [12]
Of vanadium total of 25 isotopes and nuclear isomer further 6 are
known. [22] Of these, two occur naturally. These are the isotopes 50V
with a natural frequency of 0.25% and 51V at a frequency of 99.75%.
50V is slightly radioactive, it decays with a half-life of 1.5 x 1017
years to 83% below to Electron 50Ti, 17% in β - decay can be used 50cr
[22] Both cores for studies with NMR spectroscopy. be.
The artificial isotopes are stable 48V with a half life of 16 days and
49v with a half-life of 330 days. These are used as tracers. [16] All
other isotopes and nuclear isomer is very unstable and decompose in
minutes or seconds.
→ List of vanadium isotopes

Pure vanadium is used only a small percentage due to its low neutron
capture as a cladding material for nuclear fuel. [23] but it can also
be more stable vanadium alloys are used. About 90% of production is
used in a variety of alloys, usually with the metals iron, titanium,
nickel, chromium, aluminum and manganese. Only a small part in
compounds, mostly as vanadium (V) oxide is used.

Gun made of chrome-vanadium steel.
With 85% of vanadium produced the vast majority is consumed in the
steel industry. Since no high purities are required, Ferro vanadium is
used as raw material. Vanadium increases in small quantities in
steels, the strength and toughness and hence the wear resistance. This
is caused by the formation of hard vanadium carbide. Depending on the
application of different amounts of vanadium are added. Structural
steels and tool steels thus contain only small amounts (0.2 to 0.5%),
vanadium, high speed steel up to 5%. [14] Vanadium steels are mainly
used for mechanically stressed tools and springs. Steels containing,
in addition to iron and vanadium and cobalt are magnetic.
Titanium alloys, which also usually contain vanadium and aluminum, are
extremely stable and heat resistant and are used in aircraft for
structural components and turbine blades of aircraft engines. [12]
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
A preliminary test provides the phosphorus salt bead, with the
vanadium in the reduction characteristic green flame appears. The
oxidizing flame is pale yellow and thus nonspecific. [24]
A qualitative test for vanadium based on the formation of
Peroxovanadiumionen. To an acidic solution, the vanadium in the +5
oxidation state will contain, mixed with a little hydrogen peroxide.
This forms the reddish-brown [V (O2)] 3 + cation. This reacts with
larger amounts of hydrogen peroxide to pale yellow Peroxovanadiumsäure
H3 [VO2 (O2) 2] [24].
Vanadium can be quantitatively determined by titration. This one
vanadium-containing sulfuric acid solution with potassium permanganate
is oxidized to pentavalent vanadium and then back-titrated with iron
(II) sulfate solution and diphenylamine as indicator. Also, a
reduction of pentavalent vanadium present with iron (II) sulfate to
tetravalent oxidation state, followed by potentiometric titration with
potassium permanganate solution is possible. [12]
In the modern analysis of vanadium can be detected by several methods.
These include atomic absorption spectrometry at 318.5 nm and the
spectrophotometry with N-benzoyl-N-phenylhydroxylamine as a color
reagent at 546 nm [14]

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