A cryogenic fluorescence spectroscopic study of uranyl carbonate, phosphate and oxyhydroxide minerals

Abstract

Uranium / Fluorescence / Cryogenic temperature / Time-resolved / Carbonate / PhosphateSummary. In this work we applied time-resolved laserinduced fluorescence spectroscopy (TRLIF) at both room temperature (RT) and near liquid-helium temperature (6 K) to characterize a series of natural and synthetic minerals of uranium carbonate, phosphate and oxyhydroxides including rutherfordine, zellerite, liebigite, phosphuranylite, meta-autunite, meta-torbernite, uranyl phosphate, sodiumuranyl-phosphate, becquerelite, schoepite, meta-schoepite, dehydrated schoepite and compreignacite, and have compared the spectral characteristics among these minerals as well as our previously published data on uranyl silicates. For the carbonate minerals, the fluorescence spectra of rutherfordine showed significant difference from those of zellerite and liebigite. The fluorescence spectra of the phosphate minerals closely resemble each other despite the differences in their composition and structure. For all uranium oxyhydroxides, the fluorescence spectra are largely red-shifted as compared to those of the uranium carbonates and phosphates and their vibronic bands are broad and less resolved at RT. The enhanced spectra resolution at 6 K allows more accurate determination of the fluorescence band origin and offers a complemental method to measure the O=U=O symmetrical stretch frequency, ν 1 , from the spacings of the vibronic bands of the fluorescence spectra. The average ν 1 values appear to be inversely correlated with the average pK a values of the anions.

Characterization of uranium-contaminated sediments from beneath a nuclear waste storage tank from Hanford, Washington: Implications for contaminant transport and fate

“…11). In contrast to the pattern manifested by uranyl silicates, we found bands in the spectra of the 6A sample that are sharper and narrower, which are more consistent with uranyl phosphates (Wang et al, 2008). Hydrous forms of sodium uranyl phosphate, such as sodium meta-autunite and autunite [Na 2 (UO 2 ) 2 (PO 4 ) 2 (H 2 O) 10-12 ], are common in both naturally weathered uranium deposits and in contaminated sediments (Finch and Murakami, 1999).…”

“…Comparison of the sharpest spectra for the unknown phases in 6C-Coarse and -Fine with well-characterized standards (Wang et al, 2005(Wang et al, , 2008 was used to ascertain the identity of the unknown uranyl phases (Fig. 10).…”

Determining individual mineral contributions to U(VI) adsorption in a contaminated aquifer sediment: A fluorescence spectroscopy study

“…Such a m 1 value is typical for U(VI) silicate minerals (Wang et al, 2008), providing additional evidence for inner-sphere U(VI) complexation with deprotonated surface silanol groups.…”

On the photo and thermally stimulated luminescence properties of U doped SrBPO 5

“…3(b)). The band at 502 nm is attributed to zero phonon (ZP) transitions from first excited level of triplet 3 P u to the ground state 1 Sg + of UO 2 2+ , while other bands are associated with transition from excited state to various higher vibronic levels in ground state [24,25]. The transitions from the first excited electronic level to the ground singlet that is often referred to as the zero-phonon transition and the vibrational levels associated with the singlet.…”