Bond orientations in uranyl nitrate hexahydrate using attenuated total reflection

Deane, A.M.; Richards, E.W.T.; Stephen, I.

doi:10.1016/0371-1951(66)80029-2

Cited by 10 publications

(8 citation statements)

References 8 publications

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“…A portion of the chemical transformation spectrum is also displayed in Figure for the very strong reststrahlen feature shifting (first as a shoulder) to higher frequencies and ultimately resulting in a doublet band with peaks at 957 and 966 cm –1 . We ascribe the original upward-going peak (seen at 949.0 cm –1 in the earliest spectra) to the reststrahlen band associated with the ν 3 band of the asymmetric uranyl stretch of the parent hexahydrate . These are some of the same UO 2 2+ IR bands that were first seen in absorption mode for UNH by Gatehouse and Comyns and Allpress and Hambly as well as for several analogous uranyl complexes as studied later by other workers. − ,, This band is typical of a reststrahlen band in that it displays quite a large reflectivity often seen for bands with strong absorption features. − ,− For the earliest time slices in Figure , adjacent to the 949 cm –1 band is a minimum at 975 cm –1 , seen as a sharp drop in reflectivity occurring on the high frequency side of the ν 3 reststrahlen band.…”

Section: Resultsmentioning

confidence: 58%

“…Nevertheless, assuming upward-going peaks for the experimental data, it is seen that the absolute frequencies are in reasonably good agreement, and the observed frequency shifts upon dehydration from UNH to UNT are in very good agreement for this part of the spectrum. Many of these bands have been previously assigned primarily as NO 3 – modes , and are noted in Table . Bullock also investigated these by studying the spectra as both the ligand L and cation M were varied in complexes of the form M x UO 2 L y (NO 3 ) 2 .…”

Section: Resultsmentioning

confidence: 99%

“…The infrared spectra of UNH along with the related compounds UNT and UND have been reported many times. ,− ,,− However, almost all previous papers report transmission measurements only, and most of these show two absorption peaks for the asymmetric UO 2 2+ stretch in the vicinity of 950 cm –1 . The two peaks are usually separated by ∼30 cm –1 , and both are ascribed to the ν 3 IR-active asymmetric stretch, distinct from the ν 1 symmetric uranyl stretch , near 875 cm –1 .…”

Section: Discussionmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 58%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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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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“…The binding between uranyl and the adsorbents was then investigated by FT-IR. When comparing to the spectrum of uranyl nitrate, which has a distinct peak at 935 cm –1 corresponding to the asymmetric stretch of O  UO (Figure S13), the spectra for the uranium-contacted adsorbents have an obvious shift to ∼904 cm –1 (Figures S14 and B). This red shift for the peak associated with uranyl is indicative of strong binding between it and the adsorbents.…”

Section: Resultsmentioning

confidence: 99%

Design Strategies to Enhance Amidoxime Chelators for Uranium Recovery

Aguila

Sun

Cassady

et al. 2019

ACS Appl. Mater. Interfaces

105

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To move nuclear as a primary energy source, uranium resources must be secured beyond what terrestrial reserves can provide. Given the vast quantity of uranium naturally found in the ocean, adsorbent materials have been investigated to recover this vital fuel source. Amidoxime (AO) has been found to be the state-of-theart functional group for this purpose, however, improvements must still be made to overcome the issues with selectively capturing uranium at such a low concentration found in the ocean. Herein, we report PAF-1 as a platform to study the effects of two amidoxime ligands. The synthesized adsorbents, PAF-1-CH 2 NHAO and PAF-1-NH(CH 2 ) 2 AO, with varying chain lengths and grafting degrees, were investigated for their uranium uptakes and kinetic efficiency. PAF-1-NH(CH 2 ) 2 AO was found to outperform PAF-1-CH 2 NHAO, with a maximum uptake capacity of 385 mg/g and able to reduce a uranium-spiked solution to ppb level within 10 min. Further studies with PAF-1-NH(CH 2 ) 2 AO demonstrated effective elution for multiple adsorption cycles and showed promising results for uranium recovery in the diverse composition of a spiked seawater solution. The work presented here moves forward design principles for amidoxime-functionalized ligands and provides scope for strategies to enhance the capture of uranium as a sustainable nuclear fuel source.

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“…One of these frequencies observed in the earliest time-slice spectra (seen at 949 cm -1 ) is an upward-going reststrahlen peak that we ascribe to the ν3 band of the asymmetric uranyl stretch of the parent hexahydrate. 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.…”

Section: Resultsmentioning

confidence: 73%

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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Bond orientations in uranyl nitrate hexahydrate using attenuated total reflection

Cited by 10 publications

References 8 publications

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

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

Design Strategies to Enhance Amidoxime Chelators for Uranium Recovery

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

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