Infra-Red Spectra of Uranyl Compounds. I. Uranyl Nitrates

Allpress, J.G.; Hambly, AN

doi:10.1071/ch9590569

Cited by 39 publications

(14 citation statements)

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“…27 The same UO2 2+ infrared band has been observed in transmission for similar (but not exact) frequencies many decades ago and ascribed to UNH. 6,7 Similar frequencies for the asymmetric uranyl stretch have also been observed and ascribed for many analogous uranyl salts and complexes by other researchers. [7][8][9]28 The reflectance band is typical for a reststrahlen band in that it displays quite a large reflectivity.…”

Section: Resultssupporting

confidence: 55%

“…More than a half-century ago, these various hydrates were all studied by infrared transmission spectroscopy, but were limited both by the instrumental resolution of the day and (we surmise) by the inability to prepare the samples as transmission mulls or pellets without affecting the sample. [6][7][8][9] In this study we use an alternate method that does not require pellet preparation (and, we suspect, consequent desiccation of the material). Instead we employ time-resolved infrared spectroscopy in reflectance mode.…”

Section: Introductionmentioning

confidence: 99%

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Dehydration of uranyl nitrate hexahydrate to uranyl nitrate trihydrate under ambient conditions as observed via dynamic infrared reflectance spectroscopy

et al. 2015

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Uranyl nitrate is a key species in the nuclear fuel cycle, but is known to exist in different states of hydration, including the hexahydrate [UO2(NO3)2(H2O)6] (UNH) and the trihydrate [UO2(NO3)2(H2O)3] (UNT) forms. Their stabilities depend on both relative humidity and temperature. Both phases have previously been studied by infrared transmission spectroscopy, but the data were limited by both instrumental resolution and the ability to prepare the samples as pellets without desiccating it. We report time-resolved infrared (IR) measurements using an integrating sphere that allow us to observe the transformation from the hexahydrate to the trihydrate simply by flowing dry nitrogen gas over the sample. Hexahydrate samples were prepared and confirmed via known XRD patterns, then measured in reflectance mode. The hexahydrate has a distinct uranyl asymmetric stretch band at 949.0 cm -1 that shifts to shorter wavelengths and broadens as the sample dehydrates and recrystallizes to the trihydrate, first as a blue edge shoulder but ultimately resulting in a doublet band with reflectance peaks at 966 and 957 cm -1 . The data are consistent with transformation from UNH to UNT since UNT has two non-equivalent UO2 2+ sites. The dehydration of UO2(NO3)2(H2O)6 to UO2(NO3)2(H2O)3 is both a morphological and structural change that has the lustrous lime green crystals changing to the dull greenish yellow of the trihydrate. Crystal structures and phase transformation were confirmed theoretically using DFT calculations and experimentally via microscopy methods. Both methods showed a transformation with two distinct sites for the uranyl cation in the trihydrate, as opposed to a single crystallographic site in the hexahydrate.

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Section: Resultssupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Dehydration of uranyl nitrate hexahydrate to uranyl nitrate trihydrate under ambient conditions as observed via dynamic infrared reflectance spectroscopy

et al. 2015

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“…However, while infrared transmission of UNH was studied long ago, − the dehydration processes of this material have never been studied by reflectance spectroscopy, nor ab initio quantum mechanical methods. By determining the hydration–desiccation state of the uranyl nitrate phases, and monitoring these changes with reflectance infrared spectroscopy, it may be possible to better understand these phases’ chemical states.…”

Section: Introductionmentioning

confidence: 99%

“…By determining the hydration–desiccation state of the uranyl nitrate phases, and monitoring these changes with reflectance infrared spectroscopy, it may be possible to better understand these phases’ chemical states. Earlier work on the phases of uranyl nitrates typically used transmission infrared spectroscopy with specimens mixed as Nujol mulls or pressed into IR-transparent KBr pellets. ,− The early studies were limited in their ability to distinguish the nature of these uranyl phases due in part to lower spectral resolution of the day and in part due to the requisite sample manipulation needed for transmission measurements. As a result, we have revisited these studies to assess the change in phase with relative humidity for the IR spectra and the thresholds for such conditions.…”

Section: Introductionmentioning

confidence: 99%

Time-Resolved Infrared Reflectance Studies of the Dehydration-Induced Transformation of Uranyl Nitrate Hexahydrate to the Trihydrate Form

et al. 2015

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Uranyl nitrate is a key species in the nuclear fuel cycle. However, this species is known to exist in different states of hydration, including the hexahydrate ([UO2(NO3)2(H2O)6] often called UNH), the trihydrate [UO2(NO3)2(H2O)3 or UNT], and in very dry environments the dihydrate form [UO2(NO3)2(H2O)2]. Their relative stabilities depend on both water vapor pressure and temperature. In the 1950s and 1960s, the different phases were studied by infrared transmission spectroscopy but were limited both by instrumental resolution and by the ability to prepare the samples for transmission. We have revisited this problem using time-resolved reflectance spectroscopy, which requires no sample preparation and allows dynamic analysis while the sample is exposed to a flow of N2 gas. Samples of known hydration state were prepared and confirmed via X-ray diffraction patterns of known species. In reflectance mode the hexahydrate UO2(NO3)2(H2O)6 has a distinct uranyl asymmetric stretch band at 949.0 cm(-1) that shifts to shorter wavelengths and broadens as the sample desiccates and recrystallizes to the trihydrate, first as a shoulder growing in on the blue edge but ultimately results in a doublet band with reflectance peaks at 966 and 957 cm(-1). The data are consistent with transformation from UNH to UNT as UNT has two inequivalent UO2(2+) sites. The dehydration of UO2(NO3)2(H2O)6 to UO2(NO3)2(H2O)3 is both a structural and morphological change that has the lustrous lime green UO2(NO3)2(H2O)6 crystals changing to the matte greenish yellow of the trihydrate solid. The phase transformation and crystal structures were confirmed by density functional theory calculations and optical microscopy methods, both of which showed a transformation with two distinct sites for the uranyl cation in the trihydrate, with only one in the hexahydrate.

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“…), and can also be used for quantitative analysis of solution samples without special treatment [16]. Generally, with the strengthening of coordination, the O=U=O bond of uranyl ion weakens, and the v as in the IR spectra shows a red shift [17][18][19]. Wu In this paper, the spectroscopic and electrochemical behavior of the complex formed by urea ligands with uranyl and europium(III) was investigated.…”

Section: Electronic Supplementary Materialsmentioning

confidence: 99%

Spectroscopic and electrochemical studies on the complexes of urea ligands with uranyl (VI) and europium (III) in ionic liquid

Guo

Liu

et al. 2020

J Radioanal Nucl Chem

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The spectroscopic and electrochemical behavior of the complex of tetraalkylurea ligands with uranyl(VI) and europium(III) in ionic liquid 1-butyl-3-methylimidazolium bis(tri-fluoromethylsulfonyl)imide ([Bmim][NTf 2 ]) was studied. As the steric hindrance of the substituent increases, the number of ligands in the [UO 2 (L) n ] 2+ complex decreases, however, Eu(III) maintains 8-coordinated complexes [Eu(L) 8 ] 3+ . The effect of urea ligands on the redox potential of Eu(III) is significantly greater than that of UO 2 2+ . Tetrabutylurea can better stabilize the low-valence Eu(II) and improve the redox reversibility of UO 2 2+ .

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Infra-Red Spectra of Uranyl Compounds. I. Uranyl Nitrates

Cited by 39 publications

References 0 publications

Dehydration of uranyl nitrate hexahydrate to uranyl nitrate trihydrate under ambient conditions as observed via dynamic infrared reflectance spectroscopy

Dehydration of uranyl nitrate hexahydrate to uranyl nitrate trihydrate under ambient conditions as observed via dynamic infrared reflectance spectroscopy

Time-Resolved Infrared Reflectance Studies of the Dehydration-Induced Transformation of Uranyl Nitrate Hexahydrate to the Trihydrate Form

Spectroscopic and electrochemical studies on the complexes of urea ligands with uranyl (VI) and europium (III) in ionic liquid

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