Selenates and Selenites

Selenates and Selenites.—The separation of selenate and selenite ions by circular paper chromatography has been described.299 The significance of 

Elements of Group VI suitable eluents and the migration behaviour of selenate and selenite ions was brought out, and a method for the clear separation of the ions by the technique of precipitation chromatography described. 

The atomic positions of the paraelectric phase of crystalline NaNH4-Se04,2H20 have been determined by X-ray diffraction methods.300 The positions of the hydrogen atoms were unambiguously established by the n.m.r. spectrum of the partially deuteriated crystal. A low-temperature X-ray diffraction study301 of potassium selenate, K2Se04, has shown the existence of a superstructure in the low-temperature phases formed at 129.5 and 93 K. The superstructure is attributed to rather small atomic displacements parallel to the a-plane. 

Al2(Se04)3,18H20 + 3BaCl2 — 3BaSe04 + 2A1C13 +18H20 (82) 

The effect on the phase transitions of the application of an electric313 field to Na(DIHi I)3(Se03)2, and of irradiation with a large dose of gamma radiation314 of NaH3(Se03)2, has been studied. 

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Alanyahoglu M, Demir U, Shannon C (2004) Electrochemical formation of Se atomic layers on Au(lll) surfaces the role of adsorbed selenate and selenite. J Electroanal Chem 561 21-27... 

Van Fleet-Stalder V, TG Chasteen, IJ Pickering, GN George, RC Prince (2000) Pate of selenate and selenite metabolized by Rhodobacter sphaeroides. Appl Environ Microbiol 66 4849-4853. 

Selenium, in the form of selenate or selenite, is toxic to D. desulfuricans (Tomei et al. 1995) and Wolinella succinogenes (Tomei et al. 1992) at elevated levels. At sublethal levels of 0.1-1. OmM selenite or 10 mM selenate, minimal levels of growth is observed with both D. desulfuricans and Wolinella succinogenes. With both selenate and selenite, colloidal elemental selenium (Se°) is produced inside the cell and released into the culture fluid after cell death. This reduction of Se(VI) and Se(IV) by these anaerobes is not coupled to growth and proceeds by mechanisms that have not yet been identified. Selenite and selenate reduction with formation of elemental selenium by these nonrespiratory processes serve to detoxify the environment for future bacteria and may be important for the geochemical cycle of selenium. 

Tomei FA, Barton LL, Lemanski CL, Zocco TG. 1992. Reduction of selenate and selenite to elemental selenium by Wolinella succinogenes. Can J Microbiol 38 1328-33. 

Su, C. Suarez, D.L. (2000) Selenate and selenite sorption on iron oxides An infrared and electrophoretic study. Soil Sci. Soc. Am. J.101-111... 

Zhang, P.C. Sparks, D.L. (1990) Kinetics and mechanism of sulfate adsorption and desorption on goethite using pressure jump relaxation. Soil Sci. Soc. Am. J. 54 1266-1273 Zhang, P.C. Sparks, D.L. (1990) Kinetics of selenate and selenite adsorption/desorption at the goethite/water interface. Environ. Sci. Technol. 24 1848-1856... 

Zhang, R-C. and Sparks, D.L. (1990) Kinetics of selenate and selenite adsorption/ desorption at the goethite/water interface. Environ. Sci. Technol., 24, 1848-1856. 

Inorganic and organic selenium have been reported to loca ze in several types of human tumors (62, 63) Uptake of both Se selenate and selenite were similar (64) Ehrlich carcinoma,... 

Arvy, M.P. 1993. Selenate and selenite uptake and translocation in bean plants (Phaseolus vulgaris). Journal of Experimental Botany, 44 1083-7. 

Anaerobic reduction of Se04 and SeO to Se° and methylated selenides Selenate and selenite reduction by microorganisms has been noted for some time. Organisms with this capacity include bacteria and fungi (Trudinger et al., 1979 Stolz Oremland, 1999). In bacteria the reductions are mostly a form of anaerobic respiration and result in selenium immobilization with the formation of water-insoluble Se°. In fungi the reductions involve the formation of methylated selenium,... 

Selenates, selenites, and tellurates. Uranyl selenates and selenites have been prepared and can be expected to have the same coordination features as the sulfates and sulfites. In addition to the selenate, U02Se04, the ternary selenite (U02)2(OH)2(Se03), has been reported to form in... 

Figure 5. Evidence for surface species (right) in the normalized, background-subtracted, k3-weighted EXAFS spectra (left) of selenate and selenite ions reacted with goethite. The EXAFS spectra of selenate or selenite ions in aqueous solution are shown as dashed curves, with vertical arrows denoting contributions from Fe(III) in the selenite spectrum. Reactive surface OH groups on goethite are...

Dungan, R. S., Yates, S. R. and Frankenberger, W. T., Jr. (2003). Transformations of selenate and selenite by Stenotrophomonas maltophilia isolated from a seleniferous agricultural drainage pond sediment. Environ. Microbiol. 5, 287-295. 

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