Vanadium pentoxide

ration (Greenberg et al., 1990), by GF–AAS with preconcentration (Ishida et al., 1989;

Tsukamoto et al., 1990) and by high-resolution ICP–MS (Moens et al., 1994) suggest that

the true normal vanadium concentration in blood and serum of occupationally non-

exposed populations is in the range of 0.02–0.1 

µg/L. The accuracy of the results obtained

by RNAA was confirmed by concomitant analysis of a variety of biological reference

materials and comparison of the values obtained with certified or literature values. For the

Second Generation Biological Reference Material (freeze-dried human serum), vanadium

concentrations of 0.67 

± 0.05 µg/kg (dry mass) and 0.66 ± 0.10 µg/kg (dry mass) obtained

by RNAA in two separate studies (Byrne & Versieck, 1990; Byrne & Kucera, 1991a) were

consistent with the mean of 0.83 

± 0.09 µg/kg (dry mass) obtained by high-resolution

ICP–MS (Moens et al., 1994). These values correspond to serum concentrations of

0.060–0.075 

µg/L, which are in the range of the normal vanadium concentrations in blood

and/or serum suggested above. [The concentration in 

µg/kg dry mass can be converted

into a concentration in 

µg/L by dividing by a factor of 11 (Versieck et al., 1988).] 

Vanadium concentrations in urine of occupationally non-exposed populations deter-

mined by RNAA (Kucera et al., 1994) and by GF–AAS with preconcentration (Buchet

et al., 1982; Buratti et al., 1985; Ishida et al., 1989; Minoia et al., 1990) have been shown

consistently to have mean values ranging from 0.2 to 0.8 

µg/L.

1.2

Production and use

1.2.1

Production

Although vanadium is widely dispersed and relatively abundant in the earth’s crust,

deposits of ore-grade minable vanadium are rare (see Section 1.3.1). The bulk of vana-

dium production is derived as a by-product or coproduct in processing iron, titanium,

phosphorus and uranium ores. Vanadium is most commonly recovered from these ores in

the form of pentoxide, but sometimes as sodium and ammonium vanadates.

Only about a dozen vanadium compounds are commercially significant; of these,

vanadium pentoxide is dominant (Woolery, 1997; Nriagu, 1998; O’Neil, 2001; Atomix,

2003).

Vanadium was discovered twice. In 1801, Andres Manuel del Rio named it erythro-

nium, but then decided he had merely found an impure form of chromium. Independently,

Nils Gabriel Sefstrom found vanadium in 1830, and named it after the Scandinavian

goddess of beauty and youth — the metal’s compounds provide beautiful colours in solu-

tion. Henry Enfield Roscoe first isolated the metal in 1867, from vanadium dichloride. It

was not until 1925 that relatively pure vanadium was obtained — by reducing vanadium

pentoxide with calcium metal (Atomix, 2003).

According to the US Geological Survey (2002), nearly all the world’s supply of vana-

dium comes from primary sources. Seven countries (China, Hungary, Japan, Kazakhstan,

the Russian Federation, South Africa and the USA) recover vanadium from ores, concen-

trates, slag or petroleum residues. In five of the seven countries, the mining and processing

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of magnetite-bearing ores was reported to be an important source of vanadium production.

Japan and the USA are believed to be the only countries to recover significant quantities

of vanadium from petroleum residues. World demand for vanadium fluctuates in response

to changes in steel production. It is anticipated to increase due to the demands for stronger

and lighter steels and new applications, such as the vanadium battery (Magyar, 2002).

Raw materials processed into vanadium compounds include the titanomagnetite ores

and their concentrates, which are sometimes processed directly, vanadium slags derived

from ores, oil combustion residues, residues from the hydrometallization process and

spent catalysts (secondary raw materials) (Hilliard, 1994; Bauer et al., 2003). Primary

industrial compounds produced directly from these raw materials are principally 98% (by

weight) fused pentoxide, air-dried (technical-grade) pentoxide and technical-grade

ammonium metavanadate (Woolery, 1997). 

The titanomagnetite ore in lump form, containing approximately 1.5–1.7% vanadium

pentoxide, is first reduced by coal at approximately 1000 °C in directly-heated rotary kilns.

A further reduction is then performed in an electric furnace to obtain a pig iron which

contains approximately 1.4% vanadium pentoxide. The molten pig iron is oxidized in a

shaking ladle, causing the vanadium to be transferred to the slag in the form of a water-

soluble trivalent iron spinel. A typical vanadium slag has the following approximate

composition: 14% vanadium (equivalent to 25% vanadium pentoxide), 9% metallic iron,

32% total iron, 7% silica, 3.5% manganese, 3.5% titanium, 2.5% magnesium, 2.0% alumi-

nium and 1.5% calcium. This is the world’s principal raw material for vanadium production

(Hilliard, 1994; Bauer et al., 2003).

The main process used today to produce vanadium pentoxide from vanadium slags is

alkaline roasting. The same process, with minor differences, can also be used for processing

titanomagnetite ores and vanadium-containing residues. The slag is first ground to

< 100

µm, and the iron granules are removed. Alkali metal salts are added, and the material

is roasted with oxidation at 700–850 °C in multiple-hearth furnaces or rotary kilns to form

water-soluble pentavalent sodium orthovanadate. The roasted product is leached with water,

and ammonium polyvanadate or sparingly-soluble ammonium metavanadate are precipi-

tated in crystalline form from the alkaline sodium orthovanadate solution by adding sulfuric

or hydrochloric acid and ammonium salts at elevated temperature. These compounds are

converted to high-purity, alkali-free vanadium pentoxide by roasting. The usual commercial

‘flake’ form of vanadium pentoxide is obtained from the solidified melt (Hilliard, 1994;

Bauer et al., 2003). 

Hydrometallurgical methods or a combination of pyrometallurgical and hydro-

metallurgical processes are used to produce vanadium oxides and salts from other raw

materials. In the combined processes, thermal treatment is followed by alkaline or, more

rarely, acid processing (Hilliard, 1994; Bauer et al., 2003).

Uranium production from carnotite and other vanadium-bearing ores also yields

significant amounts of vanadium pentoxide (Atomix, 2003).

Total world production of vanadium pentoxide in 1996 was approximately 131

million pounds [59 500 tonnes] (Woolery, 1997). Based on vanadium pentoxide produc-

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