Environment vanadium

From a chemical point of view, the setting for the encounter between tunicate and vanadium at the sea water interface is fairly simple to visualize. In the oxygenated, mildly alkaline, highly dilute conditions of the external sea water environment vanadium is present as monomeric vanadate anion. It is there predominantly as the free ion the low concentrations of organic chelators in sea water favor complex dissociation rather than formation (Cf. p. 141)8. ... 

Salts of vanadium, manganese, and iron are all effective catalysts for this oxidation, since all can undergo redox reactions. These species are widely distributed in various environments vanadium especially is found in particulate matter produced during coal burning (see more details for HM and SPM emissions from lignite-burning power plant in Chapter 12). 

Vanadium phosphoms oxide-based catalysts ate unstable in that they tend to lose phosphoms over time at reaction temperatures. Hot spots in fixed-bed reactors tend to accelerate this loss of phosphoms. This loss of phosphoms also produces a decrease in selectivity (70,136). Many steps have been taken, however, to aHeviate these problems and create an environment where the catalyst can operate at lower temperatures. For example, volatile organophosphoms compounds are fed to the reactor to mitigate the problem of phosphoms loss by the catalyst (137). The phosphoms feed also has the effect of controlling catalyst activity and thus improving catalyst selectivity in the reactor. The catalyst pack in the reactor may be stratified with an inert material (138,139). Stratification has the effect of reducing the extent of reaction pet unit volume and thus reducing the observed catalyst temperature (hot... 

Fluidized-bed reactor systems put other unique stresses on the VPO catalyst system. The mixing action inside the reactor creates an environment that is too harsh for the mechanical strength of a vanadium phosphoms oxide catalyst, and thus requires that the catalyst be attrition resistant (121,140,141). To achieve this goal, vanadium phosphoms oxide is usually spray dried with coUoidal siUca [7631-86-9] or polysiUcic acid [1343-98-2]. Vanadium phosphoms oxide catalysts made with coUoidal sUica are reported to have a loss of selectivity, while no loss in selectivity is reported for catalysts spray dried with polysUicic acid (140). 

A high-nickel alloy is used for increased strength at elevated temperature, and a chromium content in excess of 20% is desired for corrosion resistance. An optimum composition to satisfy the interaction of stress, temperature, and corrosion has not been developed. The rate of corrosion is directly related to alloy composition, stress level, and environment. The corrosive atmosphere contains chloride salts, vanadium, sulfides, and particulate matter. Other combustion products, such as NO, CO, CO2, also contribute to the corrosion mechanism. The atmosphere changes with the type of fuel used. Fuels, such as natural gas, diesel 2, naphtha, butane, propane, methane, and fossil fuels, will produce different combustion products that affect the corrosion mechanism in different ways. 

The properties of the zeolite play a significant role in the overall performance of the catalyst. Understanding these properties increases our ability to predict catalyst response to changes in unit operation. From its inception in the catalyst plant, the zeolite must retain its catalytic properties under the hostile conditions of the FCC operation. The reaclor/regenerator environment can cause significant changes in chemical and structural composition of the zeolite. In the regenerator, for instance, the zeolite is subjected to thermal and hydrothermal treatments. In the reactor, it is exposed to feedstock contaminants such as vanadium and sodium. 

Vanadium atom depositions were further studied in alkane matrices 109) in an effort to observe the influence of other low-temperature, matrix environments on the optical spectra and clustering properties of metal atoms. Thus, vanadium atoms were deposited with a series of normal, branched, and cyclic alkanes over a wide range of temperature. The atomic spectra were somewhat broadened compared to those in argon, but the matrix-induced, frequency shifts from gas-phase values were smaller. As shown in Fig. 3, these shifts decrease with in-... 

Carpentier W, K Sandra, I De Smet, A Brige J Van Beeuman (2003) Microbial reduction and precipitation of vanadium by Shewanella oneidensis. Appl Environ Microbiol 69 3636-3639. 

Ortiz-Bernad I, RT Anderson, HA Vrionis, DR Lovley (2004b) Vanadium respiration by Geobacter metal-lireducens novel strategy for in situ removal of vanadium from groundwater. Appl Environ Microbiol... 

The mechanism by which the enantioselective oxidation occurs is generally similar to that for the vanadium-catalyzed oxidations. The allylic alcohol serves to coordinate the substrate to titanium. The tartrate esters are also coordinated at titanium, creating a chiral environment. The active catalyst is believed to be a dimeric species, and the mechanism involves rapid exchange of the allylic alcohol and /-butylhydroperoxide at the titanium ion. 

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. 

In the bulk form, vanadium oxides display different oxidation states and V—O coordination spheres and exhibit a broad variety of electronic, magnetic, and structural properties [96, 97], which make these materials attractive for many industrial applications. Prominent examples range from the area of catalysis, where V-oxides are used as components of important industrial catalysts for oxidation reactions [98] and environment pollution control [99], to optoelectronics, for the construction of light-induced electrical switching devices [100] and smart thermo-chromic windows. In view of the importance of vanadium oxides in different technological applications, the fabrication of this material in nanostructured form is a particularly attractive goal. 

Although the oxygen atom environment is common in vanadium chemistry54 it is rarely used to support the V- C functionality.55 Two significant exceptions in... 

Mackey, E.A., P.R. Becker, R. Demiralp, R.R. Greenberg, B J. Koster, and S.A. Wise. 1996. Bioaccumulation of vanadium and other trace metals in livers of Alaskan cetaceans and pinnipeds. Arch. Environ. Contam. Toxicol. 30 503-512. 

Hoffman, D.J. 1979. Embryotoxic effects of crude oil containing nickel and vanadium in mallards. Bull. Environ. Contam. Toxicol. 23 203-206. 

Munch, D. 1993. Concentration prohles of arsenic, cadmium, chromium, copper, lead, mercury, nickel, zinc, vanadium and polynuclear aromatic hydrocarbons (PAH) in forest soil beside an urban road. Sci. Total Environ. 138 47-55. 

U.S. Environmental Protection Agency (USEPA). 1975. Preliminary investigation of effects on the environment of boron, indium, nickel, selenium, tin, vanadium and their compounds. Volume III. Nickel. U.S. Environ. Protection Agen. Rep. 560/2-75-005c. 89 pp. 

Anonymous. 1975. Preliminary Investigation of Effects on the Environment of Boron, Indium, Nickel, Selenium, Tin, Vanadium and Their Compounds. Vol. IV. Selenium. U.S. Environ. Protection Agency Rep. 560/2-75-005d. Available as PB — 245 987 from Nat. Tech. Inform. Serv., U.S. Dept. Commerce, Springfield, VA. 92 pp. 

Boisson, F., M. Gnassia-Barelli, and M. Romeo. 1995. Toxicity and accumulation of selenite and selenate in the unicellular marine algae Cricosphaera elongata. Arch. Environ. Contamin. Toxicol. 28 497-493. Bovee, E.C. and T.L. O Brien. 1982. Some effects of selenium, vanadium and zirconium on the swimming rate of Tetrahymena pyriformis a bioassay study. Univ. Kans. Sci. Bull. 52 (4) 39 44. 

VHOCs was also observed in response to grazing pressure in Ascophyllum nodosum beds (Nightingale et al. 1995). Their biogenesis involves vanadium haloperoxi-dases (vHPO), which catalyse the oxidation of halides (X ) and generate X+ to yield hypohalous acid (XIO) and other forms of oxidized halides (X2, X2 ). Marine organisms and especially seaweeds have been known for a long time to concentrate halides from their environment (for a recent review, see Leblanc et al. 2006). 

Leblanc C, Colin C, Cosse A, Delage L, La Barre SL, Morin P, Fievet B, Voiseux C, Ambroise Y, Verhaeghe E, Amouroux D, Donard O, Tessier E, Potin P (2006) Iodine transfers in the coastal marine environment the key role of brown algae and of their vanadium-dependent haloperoxi-dases. Biochimie 88 1773-1785... 

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