Vanadium
Vanadium
is a rare, soft, ductile gray-white element found combined in certain
minerals and used mainly to produce certain alloys. Vanadium resists
corrosion due to a protective film of oxide on the surface. Common
oxidation states of vanadium include +2, +3, +4 and +5.
Applications
Most of the vanadium (about 80%) produced is used as ferrovanadium or as a
steel additive. Mixed with aluminium in titanium alloys is used in jet
engines and high speed air-frames, and steel alloys are used in
axles, crankshafts, gears and other critical components. Vanadium alloys
are also used in nuclear reactors because vanadium has low
neutron-adsorption abilities and it doesn not deform in creeping under
high temperatures.
Vanadium
oxide (V2O5) is used as a catalyst in
manufacturing sulfuric acid and maleic anhydride and in making ceramics.
It is added to glass to produce green or blue tint. Glass coated with
vanadium dioxide (VO2) can block infrared radiation at some
specific temperature.
Vanadium in the environment
Vanadium
is never found unbound in nature. Vanadium occurs in about 65 different
minerals among which are patronite,
vanadinite, carnotite and bauxite. Vanadium occurs in
carbon containing deposits such as crude oil, coal, oil shale and tar
sands.
Various vanadium ores are known but none is mined as such for the metal,
which is generally obtained as a byproducts of other ores. The largest
resources of vanadium are to be found in South Africa and in Russia.
World production of vanadium ore is around 45.000 tonnes a year.
Production of the metal itself comes to about 7000 tonnes per year.
Watering is an important way in which vanadium is redistributed around
the environment because venedates are generally very soluble.
Vanadium
is abundant in most soils, in variable amounts, and it is taken up by
plants at levels that reflect its availability.
In
biology, a vanadium atom is an essential component of some enzymes,
particularly the vanadium nitrogenase used by some
nitrogen-fixing microorganisms.
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Vanadium compounds are not regarded as
serious hazard, however, workers exposed to vanadium peroxide
dust were found to suffer severe eye, nose and throat
irritation.
The uptake of vanadium by humans mainly takes
place through foodstuffs, such as buckwheat, soya beans, olive
oil, sunflower oil, apples and eggs.
Vanadium can have a number of effects on human health, when the
uptake is too high. When vanadium uptake takes places through air
it can cause bronchitis and pneumonia.
The acute effects of vanadium are irritation of lungs, throat,
eyes and nasal cavities.
Other health effects of vanadium uptake are:
- Cardiac and vascular disease
- Inflammation of stomach and intestines
- Damage to the nervous system
- Bleeding of livers and kidneys
- Skin rashes
- Severe trembling and paralyses
- Nose bleeds and throat pains
- Weakening
- Sickness and headaches
- Dizziness
- Behavioural changes
The health
hazards associated with exposure to vanadium are dependent on its
oxidation state. This product contains elemental vanadium.
Elemental vanadium could be oxidized to vanadium pentoxide
during welding. The pentoxide form is more toxic than the elemental form. Chronic exposure to vanadium
pentoxide dust and fumes
may cause severe irritation of the eyes, skin, upper respiratory
tract, persistent inflammations of the trachea and
bronchi, pulmonary edema,
and systemic poisoning. Signs and
symptoms of overexposure include; conjunctivitis,
nasopharyngitis, cough, labored breathing, rapid heart beat,
lung changes, chronic bronchitis, skin pallor,
greenish-black tongue and an allergic
skin rash. |
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Vanadium can be found in the environment in
algae, plants, invertebrates, fishes and many other species. In
mussels and crabs vanadium strongly bioaccumulates, which can lead
to concentrations of about 105 to 106 times
greater than the concentrations that are found in seawater.
Vanadium causes the inhibition of certain enzymes with animals,
which has several neurological effects. Next to the neurological
effects vanadium can cause breathing disorders, paralyses and
negative effects on the liver and kidneys.
Laboratory tests with test animals have shown, that vanadium
can cause harm to the reproductive system of male animals, and
that it accumulates in the female placenta.
Vanadium can cause DNA alteration in some cases, but it cannot
cause cancer with animals.
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periodic elements.
Recommended daily intake of
vanadium |
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