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The Elements in the Second Rank

11 Vanadium

11.1 Identity

Table 11.1
CAS No., EINECS No. and molecular weight for vanadium

11.2 Physico-chemical properties

Vanadium is found in group VA in the periodic table. The metal can have the valences +2 and +5 (V(II) to V(V)) [1]. In water vanadium is normally found as the vanadyl (V(IV)) or vanadate ion (V(V)). Chemical compounds based on the vanadate ion are normally water soluble. Vanadium is attacked by sulphuric acid and nitric acid [1]. Selected physico-chemical data for vanadium are shown in Table 11.2.

Table 11.2
Physico-chemical data for metallic vanadium. Data from [1, 3, 12, 21]

11.3 Uses and consumption

11.3.1 Uses

Vanadium is primarily used as alloy metal. It increases the hardness of steel and is found in up to 5% in titanium alloys, 2 % in hard steel, 0.03 % in trade steel and 0.08 % in other steel [2]. Vanadium is used in catalytic converters (V₂O₅) and in e.g. pigments (BiVO₄) [9]. Vanadium is also found as vanadium carbide and is furthermore used in some types of wires and metal plates where ductility is required [16]. The use of organic vanadium compounds has also been reported [17].

Vanadium is used in many dietary supplements and in vitamin tablets [14, 15].

Vanadium is also used as pigment in pottery, ceramics and colourful precious stones [18, 19].

11.3.2 Consumption

The steel industry is the most important purchaser of vanadium [9].

The global production of new vanadium was approximately 35,000 tons/year in 1990. The production has thus tripled since the 1960's. Based on the per capita-consumption in USA, the consumption in Denmark is estimated be to approximately 95 tons.

Table 11.3
The relative distribution of the vanadium use in USA and the estimated consumption in Denmark in 1998 based on [9]

Recovery is primarily from catalytic converters. Vanadium is produced from oil ash in some countries. In Sweden, high alloy steel (which contains 1.5-3.5 % vanadium) is remelted to vanadium steel [9].

11.4 Emissions and environmental concentrations

By weathering, a considerable amount of vanadium is emitted to the environment. The amount is 0.6 million tons/year on a global scale [13]. Point source emission of vanadium is observed from metallurgic manufacturing facilities.

Burning of fossil fuels is the most important anthropogenic source of vanadium emission to the atmosphere [7]. Vanadium is emitted from coal-fired power plants and when combusting oil for house heating. These sources are considered the most important sources of vanadium emission in Denmark. From the annual use of coal in Denmark in 2000 of 6.7´ 10⁶ tons [20] and an average vanadium content of 10-60 mg/kg [9], the amount of vanadium in emissions and residuals from coal-based power generation is 67-400 tons. Oil can contain up to 400 mg/kg.

In Europe, the atmospheric emission from anthropogenic sources is estimated to 34,500 tons/year. Atmospheric emissions are introduced into the aquatic and terrestrial environments by both dry and wet deposition [7].

The background level of vanadium in the earth crust is high. In the aquatic environment the background level is at the lower µg/L-level, see Table 11.4.

Table 11.4
Typical background concentration of vanadium in the environment. Data from [4, 6, 13]

A Swedish study showed that the concentration of vanadium in different types of waste was not higher than e.g. the background level in sediment [9]. The concentration of vanadium is high in the Danish waste streams compared to the other metals discussed in this report, see Table 11.5.

The vanadium concentration in wastewater has been reported to be 1.6-6.5 and 2.1-2.8 µg/L for influent and effluent, respectively [4]. The concentration in dewatered sewage sludge is 4.5-25.7 mg/kg [4], see also Table 11.5.

Table 11.5
Levels of vanadium in selected emissions and waste products from measurements conducted as part of this study in the autumn of 2001.

11.5 Danger classification

Vanadium pentaoxide (V₂O₅) is on the list of dangerous compounds and is classified as harmful, irritant, and mutagenic in category 3 (Mut3), toxic with danger of serious damage to health by prolonged exposure through inhalation, and reprotoxic in category 3 (Rep3) [10]. Vanadium pentaoxide is furthermore classified as dangerous for environment with risk phrases R51/53 (toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment) [10]. Vanadyl pyrofosfate is sensitizing and divanadyl pyrofosfate is sensitizing and toxic to aquatic organisms and may cause long-term adverse effects in the aquatic environment.

Table 11.6 shows an overview of the classification and risk phrases for vanadium compounds.

Table 11.6
Classification and risk phrases for vanadium compounds

11.6 Toxicology

The metallic form of vanadium does not seem to pose any significant risk to human health [12]. However, some vanadium compounds exist, which are toxic and have mutagenic and reprotoxic effects. Vanadium compounds are only poorly absorbed through the gastrointestinal tract but assimilation through the lungs occurs easier. Therefore, toxic effects are normally limited to the respiratory tract. Bronchitis and pneumonia are observed after industrial exposure. Therapeutic ingestion of vanadium can cause destabilization in the gastrointestinal tract, changes in the clinical-chemical parameters related with renal function, and effects of the central nervous system. These effects are primarily observed after exposure of high concentrations of vanadium.

11.7 Environmental properties

The environmental properties of vanadium are primarily determined by the vanadyl and vanadate compounds, in e.g vanadium with redox state IV and V. Vanadium is characterised by the fact that a large fraction is bound to organic matter such as sediment. Vanadium is an essential metal to certain species of algae, and in certain bacteria vanadium can substitute molybdenum [13]. It is not known if vanadium is essential to all organisms.

11.7.1 Environmental chemistry

Vanadium is found in the atmosphere bound to particulate matter and it will be removed by both wet and dry deposition. Vanadium emitted during combustion of oil can be distributed widely due to formation of small particles with high atmospheric retention times [7].

The mobility of vanadium in soil depends on the pH-value. In neutral or poorly alkaline environments, vanadium is relatively mobile compared to other metals, whereas the mobility decreases in acidic environments. In the presence of humic acids the mobile anionic metavanadate compounds (V(V)) are transformed into cationic vanadyl compounds (V(IV)). This can result in accumulation of vanadium [7].

A certain mobility of vanadium under unsaturated, oxidizing conditions has been observed. The mobility is low under reducing conditions. Vanadium can sorb to clayey soil particles.

In the aquatic environment vanadium is found as the vanadate compounds HVO₄^2- and VO₃^- in both fresh and sea water. However, the vanadyl compounds VO²⁺ and VO(OH)⁺ dominate under reducing conditions. In the aquatic environment algae and plankton assimilate vanadium, and a considerable part of the total vanadium pool will be associated with organic material under both oxidizing and reducing conditions. Vanadium will be released in connection with degradation of organic material [7].

Vanadium can precipitate by reaction with manganese oxide and ferro hydroxide (Fe(OH)₃).

11.7.2 Environmental toxicology

The available data on environmental toxicity is limited to two tests on trout (with the compound vanadium pentaoxide). Based on these, vanadium pentaoxide should be classified as toxic to aquatic organisms.

Table 11.7
Test results for environmental toxicity

11.7.3 Bioaccumulation

Bioconcentration factors of 1,900 and 400 for plant and animal plankton, respectively, have been reported from a study in Lake Michigan. However, lower bioconcentration factors were found for other organisms [7].

Accumulation of vanadium in plants was observed in the vicinity of a rolling mill in concentration of up to 19.3 mg/kg dw, which was the double of the concentration in the controls [7].

11.8 Conclusions

Vanadium is used in alloy steel and in catalytic converters. Combustion of coal is probably the most important anthropogenic emission source. Vanadium pentaoxide is classified as mutagenic and reprotoxic in category 3. The data on vanadium environmental toxicology is limited. If the environmental toxicity data is used to classify vanadium pentaoxide, it will be classified as toxic to aquatic organisms.

11.9 References

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