Topic
Uranyl
About: Uranyl is a research topic. Over the lifetime, 7410 publications have been published within this topic receiving 153992 citations. The topic is also known as: Uranyl ion & dioxouranium(2+).
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TL;DR: In this paper, the adsorption of the uranyl ion (UO22+) in contact with amorphous silica (SiO2), γ-alumina (Al2O3), and montmorillonite surfaces was investigated using X-ray absorption fine structure (XAFS) spectroscopy to observe the local structure around the uranium atom.
420 citations
TL;DR: In this article, the authors reported a further validation of the stoichiometry and the formation constant of this complex using two analytical approaches with time-resolved laser-induced fluorescence spectroscopy (TRLFS) species detection: i) titration of a nonfluorescent uranyl tricarbonate complex solution with calcium ions, and quantitative determination of the produced fluorescent calcium complex via TRLFS; and ii) variation of the calcium concentration in the complex by competitive calcium complexation with EDTA 4−.
Abstract: Summary. We recently discovered a neutral dicalcium uranyl tricarbonate complex, Ca2UO2(CO3)3(aq.), in uranium mining related waters [1]. We are now reporting a further validation of the stoichiometry and the formation constant of this complex using two analytical approaches with time-resolved laser-induced fluorescence spectroscopy (TRLFS) species detection: i) titration of a non-fluorescent uranyl tricarbonate complex solution with calcium ions, and quantitative determination of the produced fluorescent calcium complex via TRLFS; and ii) variation of the calcium concentration in the complex by competitive calcium complexation with EDTA 4− . Slope analysis of the log (fluorescence intensity) versus log [Ca 2+ ] with both methods have shown that two calcium ions are bound to form the complex Ca2UO2(CO3)3(aq.) .T he formation constants determined from the two independent methods are: i) log β ◦ 213 = 30.45 ± 0.35 and ii) log β ◦ 213 = 30.77 ± 0.25. A bathochrome shift of 0.35 nm between the UO2(CO3)3 4− complex and the Ca2UO2(CO3)3(aq.) complex is observed in the laser-induced photoacoustic spectrum (LIPAS), giving additional evidence for the formation of the calcium uranyl carbonate complex. EXAFS spectra at the LII and LIII-edges of uranium in uranyl carbonate solutions with and without calcium do not differ significantly. A somewhat better fit to the EXAFS of the Ca2UO2(CO3)3(aq.) complex is obtained by including the U-Ca shell. From the similarities between the EXAFS of the Ca2UO2(CO3)3(aq.) species in solution and the natural mineral liebigite, we conclude that the calcium atoms are likely to be in the same positions both in the solution complex and in the solid. This complex influences considerably the speciation of uranium in the pH region from 6 to 10 in calcium-rich uranium-mining-related waters.
409 citations
TL;DR: In the absence of Pb, schoepite and becquerelite are the common initial corrosion products as mentioned in this paper, and they can dissolve completely under similar geochemical conditions.
399 citations
TL;DR: In this paper, a series of uranyl complexes KxUO2Ly(NO3)2, where L is the variable ligand (or ligands), has been prepared; it has been shown that a ligand series may be defined using the antisymmetric stretching frequency of the uranyl entity, and this series exhibits a remarkable parallelism with the spectrochemical series defined by Δ in octahedral complexes of transition metals of the first and 2nd series.
Abstract: A series of uranyl complexes KxUO2Ly(NO3)2, where L is the variable ligand (or ligands), has been prepared; it has been shown that a ligand series may be defined using the antisymmetric stretching frequency of the uranyl entity, and this series exhibits a remarkable parallelism with the spectrochemical series defined by Δ in octahedral complexes of transition metals of the 1st and 2nd series. This parallelism has been rationalized using a mixed ligand field theory in which the uranyl ion is considered subject to bonding with ligands which are arranged hexagonally in a plane equatorial to the O–U–O axis. It is shown that the large changes of ν3 and ν1 are due primarily to electron population of the φu and δu atomic orbitals of uranium. Such population is physically equivalent to the reductions AmO2+ +→AmO2+ and NpO2+ +→NpO2+, which cause a decrease of approximately 100 cm—1 in ν3. It is further shown that Δν3 = — electrostatic effect — σ(L→M) — π(L→M) ± π(M→L), where in the last term the plus sign is the ...
367 citations
367 citations