Vanadium occurrence

Other examples of vanadium occurrence in nature are the relatively high concentrations of vanadium in the blood cells of tunicates, and in the fly agaric kman ta mu taKjLa). In both cases the vanadium enrichment is especially interesting, and propably the most spectacular example of metal enrichment in nature. 

Trace amounts of vanadium have been found in meteorites and seawater, and it has been identified in the spectmm of many stars including the earth s sun. The occurrence of vanadium in oak and beech trees and some forms of aquatic sea life indicates its biological importance. 

Figure 22.2 Occurrence of various vanadate and poly vanadate species as a function of pH and total concentration of vanadium.

By far the most important ores of iron come from Precambrian banded iron formations (BIF), which are essentially chemical sediments of alternating siliceous and iron-rich bands. The most notable occurrences are those at Hamersley in Australia, Lake Superior in USA and Canada, Transvaal in South Africa, and Bihar and Karnataka in India. The important manganese deposits of the world are associated with sedimentary deposits the manganese nodules on the ocean floor are also chemically precipitated from solutions. Phosphorites, the main source of phosphates, are special types of sedimentary deposits formed under marine conditions. Bedded iron sulfide deposits are formed by sulfate reducing bacteria in sedimentary environments. Similarly uranium-vanadium in sandstone-type uranium deposits and stratiform lead and zinc concentrations associated with carbonate rocks owe their origin to syngenetic chemical precipitation. 

Iodargyrite, natural occurrence of, 22 668 Iodates, 14 374-375 Iodate solutions, 14 362 Iodic acid, 14 375 Iodide analysis, of water, 26 41 Iodide ion, 14 367-368 25 488 Iodide-refining method, 26 149 for vanadium, 25 520 Iodides, 14 374 thorium, 24 763 tungsten, 25 379-380 uranium, 25 439... 

Kentemich, T., Danneberg, G., Hundeshagen, B. and Bothe, H. (1988) Evidence for the occurrence of the alternative, vanadium-containing nitrogenase in the cyanohacterium Anabaena variabilis. PEMS Microbiol. Lett., 51, 19-24. 

Male and female mice exposed at concentrations up to 4mg/m 6 hours/day for 104 weeks had clear evidence of carcinogenicity based on increased incidences of alveolar/bron-chiolar neoplasms. In rats similarly exposed at concentrations up to 2 mg/m there was some evidence of carcinogenicity in male rats and equivocal evidence in females based on the occurrence of alveolar/bronchiolar neoplasms. Exposure to vanadium pentoxide also caused a spectrum of nonneoplastic lesions in the respiratory tract including alveolar and bronchiolar epithelial hyperplasia, inflammation, fibrosis, and alveolar histocytosis of the lung. Elyper-plasia of the bronchial lymph node occurred in female mice, and an unusual squamous metaplasia of the lung occurred in rats. ... 

Baskerville, Charles, The occurrence of vanadium, chromium, and titanium... 

Jhe distribution of beryllium, boron, titanium, vanadium, chromium, cobalt, nickel, copper, zinc, gallium, germanium, tin, molybdenum, yttrium, and lanthanum in the principal coal-producing beds of the Interior Province has been studied by the U. S. Geological Survey. Data, methods of sampling, and analyses are discussed by Zubovic and others (II, 12). This chapter discusses the occurrence of 13 of these elements with respect to geological and geochemical environments of coal deposition and chemical properties of the elements. Zinc and tin are not included in this study because they were detected in only a few samples. 

Andersson M, Conte V, Di Furia F, Moro S (1995) Vanadium Bromoperoxidases Mimicking Systems Bromohydrins Formation as Evidence of the Occurrence of a Hypobromite-Like Vanadium Complex. Tetrahedron Lett 36 2675... 

The presence of vanadium and nickel in crude oils, especially as metal porphyrin complexes, has focused much attention in the petroleum refining industry on the occurrence of these metals in feedstocks (Reynolds, 1997). Only a part of the total nickel and vanadium in crude oil is recognized to occur in porphyrin structures (Table 3-5). In general, it is assumed that about 10% w/w of the total metal in a crude oil is accommodated as porphyrin complexes although as much as 40% of the vanadium and nickel may be present as metal porphyrin complexes in petroleum. 

Unlike V(II), both the V(III) and V(IV) oxidation states are stable in water. However, neither the V(III) nor the V(IV) oxidation states are easily maintained in the presence of oxygen if the pH is neutral or above, although, under acidic conditions, both these states are rather easily maintained. Somewhat surprisingly, the V(IV) species is more readily oxidized by 02 than is the V(III) species. In aqueous acidic solution, the vanadium(III) ion exists as a hexaqua octahedral complex that can deprotonate to form the 2+ and 1+ species, dependent on pH. Additionally, di, tri and tetra polymeric forms are known. Structures have been proposed and their formation constants determined [10], The occurrence of the various polymeric forms in the presence of sulfate has also been described and is particularly relevant to concentration of vanadium by bioaccumulators [10],... 

The chemistry of vanadium is characterized by multiple oxidation states (Fig. 1). The redox chemistry of this metal undoubtedly plays a role in its biochemistry. Of the four common oxidation states, only V(III), V(IV), and V(V) are important biologically, V(II) being too reducing to exist in any known organism. The best known example of the occurrence of V(III) is in the vanadocytes of the blood of tunicates22 otherwise, vanadium is largely found in the +4 and +5 oxidation states, both of which are readily accessible under physiological conditions. 

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