Fluorescence spectroscopy of U(VI)-silicates and U(VI)-contaminated Hanford sediment

Zheming Wang, John M. Zachara, Paul L. Gassman, Chongxuan Liu, Odeta Qafoku, Wassana Yantasee, Jeff G. Catalano

Research output: Contribution to journalArticle

92 Citations (Scopus)

Abstract

Time-resolved U(VI) laser fluorescence spectra (TRLFS) were recorded for a series of natural uranium-silicate minerals including boltwoodite, uranophane, soddyite, kasolite, sklodowskite, cuprosklodowskite, haiweeite, and weeksite, a synthetic boltwoodite, and four U(VI)-contaminated Hanford vadose zone sediments. Lowering the sample temperature from RT to ∼ 5.5 K significantly enhanced the fluorescence intensity and spectral resolution of both the minerals and sediments, offering improved possibilities for identifying uranyl species in environmental samples. At 5.5 K, all of the uranyl silicates showed unique, well-resolved fluorescence spectra. The symmetric O = U = O stretching frequency, as determined from the peak spacing of the vibronic bands in the emission spectra, were between 705 to 823 cm-1 for the uranyl silicates. These were lower than those reported for uranyl phosphate, carbonate, or oxy-hydroxides. The fluorescence emission spectra of all four sediment samples were similar to each other. Their spectra shifted minimally at different time delays or upon contact with basic Na/Ca-carbonate electrolyte solutions that dissolved up to 60% of the precipitated U(VI) pool. The well-resolved vibronic peaks in the fluorescence spectra of the sediments indicated that the major fluorescence species was a crystalline uranyl mineral phase, while the peak spacing of the vibronic bands pointed to the likely presence of uranyl silicate. Although an exact match was not found between the U(VI) fluorescence spectra of the sediments with that of any individual uranyl silicates, the major spectral characteristics indicated that the sediment U(VI) was a uranophane-type solid (uranophane, boltwoodite) or soddyite, as was concluded from microprobe, EXAFS, and solubility analyses.

Original languageEnglish (US)
Pages (from-to)1391-1403
Number of pages13
JournalGeochimica et Cosmochimica Acta
Volume69
Issue number6
DOIs
StatePublished - Mar 15 2005
Externally publishedYes

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Silicates
fluorescence spectroscopy
Fluorescence spectroscopy
Sediments
fluorescence
silicate
Fluorescence
sediment
Carbonates
Minerals
spacing
Hydroxides
Silicate minerals
carbonate
Uranium
Spectral resolution
silicate mineral
mineral
spectral resolution
vadose zone

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Fluorescence spectroscopy of U(VI)-silicates and U(VI)-contaminated Hanford sediment. / Wang, Zheming; Zachara, John M.; Gassman, Paul L.; Liu, Chongxuan; Qafoku, Odeta; Yantasee, Wassana; Catalano, Jeff G.

In: Geochimica et Cosmochimica Acta, Vol. 69, No. 6, 15.03.2005, p. 1391-1403.

Research output: Contribution to journalArticle

Wang, Zheming ; Zachara, John M. ; Gassman, Paul L. ; Liu, Chongxuan ; Qafoku, Odeta ; Yantasee, Wassana ; Catalano, Jeff G. / Fluorescence spectroscopy of U(VI)-silicates and U(VI)-contaminated Hanford sediment. In: Geochimica et Cosmochimica Acta. 2005 ; Vol. 69, No. 6. pp. 1391-1403.
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