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Influence of Dynamical Conditions on the Reduction of UVI at the Magnetite--Solution Interface.

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Title: Influence of Dynamical Conditions on the Reduction of UVI at the Magnetite--Solution Interface.
Authors: ILTON, EUGENE S.1 Eugene.Ilton@PNL.gov, BOILY, JEAN-FRANÇOIS2, BUCK, EDGAR C.1, SKOMURSKI, FRANCES N.1, ROSSO, KEVIN M.1, CAHILL, CHRISTOPHER L.3, BARGAR, JOHN R.4, FELMY, ANDREW R.1
Source: Environmental Science & Technology. 1/1/2010, Vol. 44 Issue 1, p170-176. 7p.
Subject Terms: *Oxidation-reduction reaction, Chemical reduction, Scientific experimentation, Magnetite, Effect of temperature on chemical kinetics, Migration of uranium
Abstract: The heterogeneous reduction of UVI to UIV by ferrous iron is believed to be a key process influencing the fate and transport of U in the environment. The reactivity of both sorbed and structural FeII has been studied for numerous substrates, including magnetite. Published results from UVI-magnetite experiments have been variable, ranging from no reduction to clear evidence for the formation of UIV. In this contribution, we used XAS and high resolution (±cryogenic) XPS to study the interaction of UVI with nanoparticulate magnetite. The results indicated that UVI was partially reduced to UV with no evidence of UVI. However, thermodynamic calculations indicated that U phases with average oxidation states below (V) should have been stable, indicating that the system was out in redox equilibrium. A reaction pathway that involves incorporation and stabilization of UV and UVI into secondary phases is invoked to explain the observations. The results suggests an important and previously unappreciated role of UV in the fate and transport of uranium in the environment. [ABSTRACT FROM AUTHOR]
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Database: GreenFILE
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Abstract:The heterogeneous reduction of UVI to UIV by ferrous iron is believed to be a key process influencing the fate and transport of U in the environment. The reactivity of both sorbed and structural FeII has been studied for numerous substrates, including magnetite. Published results from UVI-magnetite experiments have been variable, ranging from no reduction to clear evidence for the formation of UIV. In this contribution, we used XAS and high resolution (±cryogenic) XPS to study the interaction of UVI with nanoparticulate magnetite. The results indicated that UVI was partially reduced to UV with no evidence of UVI. However, thermodynamic calculations indicated that U phases with average oxidation states below (V) should have been stable, indicating that the system was out in redox equilibrium. A reaction pathway that involves incorporation and stabilization of UV and UVI into secondary phases is invoked to explain the observations. The results suggests an important and previously unappreciated role of UV in the fate and transport of uranium in the environment. [ABSTRACT FROM AUTHOR]
ISSN:0013936X
DOI:10.1021/es9014597