Vanadium chemical forms

Under unusual circumstances, toxicity may arise from ingestion of excess amounts of minerals. This is uncommon except in the cases of fluorine, molybdenum, selenium, copper, iron, vanadium, and arsenic. Toxicosis may also result from exposure to industrial compounds containing various chemical forms of some of the minerals. Aspects of toxicity of essential elements have been pubhshed (161). 

Conversion of fused pentoxide to alloy additives is by far the largest use of vanadium compounds. Air-dried pentoxide, ammonium vanadate, and some fused pentoxide, representing ca 10% of primary vanadium production, are used as such, purified, or converted to other forms for catalytic, chemical, ceramic, or specialty appHcations. The dominant single use of vanadium chemicals is in catalysts (see Catalysis). Much less is consumed in ceramics and electronic gear, which are the other significant uses (see Batteries). Many of the numerous uses reported in the Hterature are speculative, proposed. 

Gehring AU, Fry IV, Luster J, Sposito G. 1993. The chemical form of vanadium(IV) in kaolinite. Clays and Clay Minerals 41 662-661. 

Like other amines, pyridines and anilines readily form hetero complexes, and this has provided a means of studying the influence of substituent electronegativity on vanadium chemical shifts. Hammett plots for a number of anilines and pyridines revealed a linear relationship between substituent electronegativity and chemical shifts and showed, for both classes of ligands, that51V chemical shifts became more... 

Vanadium plays an important role in many industrial catalysts used extensively in a variety of applications including the production of SO3 from SO2, selective oxidation of hydrocarbons, reduction of nitrogen oxides with ammonia, and in the manufacture of many chemicals and chemical intermediates. Such catalysts typically consist of vanadium compounds supported on oxides such as silica, alumina, titania, etc., and their activity depends on factors such as the chemical form and crystalline environment... 

The least squares refinement of this model using SHELXL-97 yields Rp = 42 % as shown in Table 6.39. All oxygen atoms and the isolated nitrogen atom look reasonable because their distances to the vanadium atoms are within acceptable limits. What is not shown in Table 6.39 is that the coordination polyhedra of V atoms make both chemical and physical sense vanadium oxide forms a layer, composed of VO5 pyramids and tetrahedral VO4, as illustrated in Figure 6.28. This layer is similar to layers known for... 

The chemical form of sulphur is important in determining the availability of metal ions in marine environments. In area I of Fig. 5.34 sulphur is generally in the form of S042 and nickel is available for bonding (as Ni2+), but vanadium is unavailable. Oils from source rocks deposited under these conditions, such as those from Mesozoic and Tertiary reservoirs in the Uinta Basin (USA), have V/(V + Ni) values <0.1 and S content <1%. In area II sulphate is again the major form of sulphur, while Ni2+ and V02+ (vanadyl) are available for bonding, but the vanadyl species may... 

VANADIUM (7440-62-2) V The finely divided material reacts with air, water, acids, alcohols may release flammable hydrogen gas and chemically basic materials. A reducing agent. Violent reaction with strong oxidizers, bromine trifluoride, chlorine, lithium, nitryl fluoride nitric, hydrofluoric, or concentrated sulfuric acids. May react with halogenated hydrocarbons, forming other reactive and possibly explosive materials. It reacts with chlorine at 356°F/180°C, forming vanadium tetrachloride. Forms water-soluble vanadates in alkalis. 

It is also becoming increasingly apparent that the specific chemical form of a metal is a factor in its toxicity. Water-lipid partitioning, cell-wall permeability, and metabolic transport are just a few of the factors influenced by chemical form which, in turn, influence toxicity. Hexavalent chromium, pentavalent vanadium, divalent manganese, arsine, and methylmercury are more toxic than other forms of the corresponding metal. ... 

Later, Chasteen, Lord, and Thompson used EPR to determine the chemical forms of both absorbed vanadium in tissue and excreted vanadium in the urine and feces of rats given VOSO4 in drinking water over long periods. EPR signals were well defined in the stomach, duodenum, liver, spleen, kidney, lung, and elimination products [78],... 

The second type of solution polymerization concept uses mixtures of supercritical ethylene and molten PE as the medium for ethylene polymerization. Some reactors previously used for free-radical ethylene polymerization in supercritical ethylene at high pressure (see Olefin POLYMERS,LOW DENSITY polyethylene) were converted for the catalytic synthesis of LLDPE. Both stirred and tubular autoclaves operating at 30—200 MPa (4,500—30,000 psig) and 170—350°C can also be used for this purpose. Residence times in these reactors are short, from 1 to 5 minutes. Three types of catalysts are used in these processes. The first type includes pseudo-homogeneous Ziegler catalysts. In this case, all catalyst components are introduced into a reactor as hquids or solutions but form soHd catalysts when combined in the reactor. Examples of such catalysts include titanium tetrachloride as well as its mixtures with vanadium oxytrichloride and a trialkyl aluminum compound (53,54). The second type of catalysts are soHd Ziegler catalysts (55). Both of these catalysts produce compositionaHy nonuniform LLDPE resins. Exxon Chemical Company uses a third type of catalysts, metallocene catalysts, in a similar solution process to produce uniformly branched ethylene copolymers with 1-butene and 1-hexene called Exact resins (56). 

Sulfur Polymer Cement. SPC has been proven effective in reducing leach rates of reactive heavy metals to the extent that some wastes can be managed solely as low level waste (LLW). When SPC is combined with mercury and lead oxides (both toxic metals), it interacts chemically to form mercury sulfide, HgS, and lead sulfide, PbS, both of which are insoluble in water. A dried sulfur residue from petroleum refining that contained 600-ppm vanadium (a carcinogen) was chemically modified using dicyclopentadiene and oligomer of cyclopentadiene and used to make SC (58). This material was examined by the California Department of Health Services (Cal EPA) and the leachable level of vanadium had been reduced to 8.3 ppm, well below the soluble threshold limit concentration of 24 ppm (59). 

Physical and Chemical Properties. Titanium dioxide [13463-67-7] occurs in nature in three crystalline forms anatase [1317-70-0] brookite [12188-41 -9] and mtile [1317-80-2]. These crystals are essentially pure titanium dioxide but contain small amounts of impurities, such as iron, chromium, or vanadium, which darken them. Rutile is the thermodynamically stable form at all temperatures and is one of the two most important ores of titanium. 

Vanadium(III) Chloride. Vanadium(III) chloride (vanadium trichloride, VCl ) is a pink-violet sohd, is readily hydrolyzed, and is insoluble in nonpolar solvents but dissolves in donor solvents, eg, acetonitrile, to form coordination compounds. Chemical behavior of the tribromide (VBr ) is similar to that of VCl. ... 

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