Spectroscopic characterization of alkaline earth uranyl carbonates

“…46 The e o energy was identified at the maximum of the absorption edge. 50 The experimental EXAFS spectrum of Liebigite recorded within the same beamline setup provided fitted parameters in agreement with the crystallographic data (Table 4). 47 Spectral noise was calculated using the CHEROKEE code 47,48 using the Fourier back transform filter above 6 Å corresponding to the noise spectrum.…”

Section: Spectroscopysupporting

confidence: 63%

XAS and TRLIF spectroscopy of uranium and neptunium in seawater

et al. 2015

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Seawater contains radionuclides at environmental levels; some are naturally present and others come from anthropogenic nuclear activity. In this report, the molecular speciation in seawater of uranium(VI) and neptunium(V) at a concentration of 5 × 10(-5) M has been investigated for the first time using a combination of two spectroscopic techniques: Time-resolved laser-induced fluorescence (TRLIF) for U and extended X-ray absorption fine structure (EXAFS) for U and Np at the LIII edge. In parallel, the theoretical speciation of uranium and neptunium in seawater at the same concentration is also discussed and compared to spectroscopic data. The uranium complex was identified as the neutral carbonato calcic complex UO2(CO3)3Ca2, which has been previously described in other natural systems. In the case of neptunium, the complex identified is mainly a carbonato complex whose exact stoichiometry is more difficult to assess. The knowledge of the actinide molecular speciation and reactivity in seawater is of fundamental interest in the particular case of uranium recovery and more generally regarding the actinide life cycle within the biosphere in the case of accidental release. This is the first report of actinide direct speciation in seawater medium that can complement inventory data.

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“…It is known from the literature that carbonate mainly binds in a bidentate fashion to uranyl in aqueous uranyl carbonate complexes, on carbonate solids such as aragonite but also in uranyl carbonates e.g. liebigite, cejkaite (Bargar et al, 2000;Catalano and Brown, 2004;Elzinga et al, 2004;Amayri et al, 2005;Kelly et al, 2007;Rossberg et al, 2009). The similarity of the EXAFS spectra of the carbonate free sample U_Mont1 and the samples U_Mont2 and U_Mont3 prepared in the presence of carbonate (Fig.…”

Section: Samplementioning

confidence: 80%