Evaluation of the Behavior of Uranium Peroxocarbonate Complexes in Na–U(VI)–CO₃–OH–H₂O₂Solutions by Raman Spectroscopy

Abstract

In this work, the formation of uranium species and their stabilities in Na-U(VI)-CO(3)-OH-H(2)O(2) solutions at different pHs are studied by Raman spectroscopy. In this solution, the UO(2)(O(2))(CO(3))(2)(4-) species was formed together with three other uranium species of UO(2)(O(2))(2)(2-), UO(2)(CO(3))(3)(4-), and a speculated uranium species of the uranyl carbonate hydroxide complex, UO(2)(CO(3))(x)(OH)(y)(2-2x-y), which showed remarkable Raman peaks at approximately 769, 848, 811, and 727 cm(-1), respectively. The UO(2)(O(2))(CO(3))(2)(4-) species disappeared at pH conditions where bicarbonate dominated, and its Raman peak could be clearly observed in only a narrow pH range from approximately 9 to 12. When the pH of the solution increased further, the UO(2)(O(2))(CO(3))(2)(4-) species changed to UO(2)(CO(3))(3)(4-) and the UO(2)(CO(3))(x)(OH)(y)(2-2x-y) species. Moreover, the UO(2)(O(2))(CO(3))(2)(4-) species continuously decomposed into uranyl tricarbonate in the carbonate solution at an elevated temperature because of the instability of the peroxide ion, O(2)(2-), in alkaline conditions.

SERS detection of uranyl using functionalized gold nanostars promoted by nanoparticle shape and size

“…3, where representative difference SERS spectra in the uranyl window (900-775 cm −1 ) for 3-MPA, 6-MHA, and 11-MUA functionalized Au nanostars are shown. Because the symmetric U-O stretch is sensitive to the coordinating ligand [49][50][51] as well as on the distance between uranyl and the gold surface, both average uranyl vibrational frequency and SERS signal intensity vary.…”

Detection and identification of solids, surfaces, and solutions of uranium using vibrational spectroscopy

“…In higher pH solutions, mixed peroxocarbonato species [UO 2 (O 2 ) x (CO 3 ) y ] 2−2x−2y forms with x:y = 1:2, 2:0, and 0:3 complexes present depending on the solution pH values [171]. Raman spectroscopy can be used to differential these complexes as the symmetric stretching bands for (UO2(O2)(CO3)24−), (UO2(CO3)34−), and (UO2(O2)22−) are centered at 769, 811, and 848 cm −1 , respectively [171]. The uranyl peroxocarbonato complex is not stable in solution for long periods of time and decomposes to the uranyl tricarbonato species under alkaline conditions or elevated temperatures (Fig.…”

Time-resolved laser fluorescence spectroscopy of UO2(CO3)34−

“…The peaks observed at 811, 934 and 1066 cm −1 correspond to the Raman bands of UO 2 (CO 3 ) 3 4− , ClO 4 − and CO 3 2− , respectively. [21][22][23][24][25] The Raman bands of UO 2 (CO 3 ) 2 2− and U-hydrolysis compounds at 834 and 850 to 870 cm −1 , respectively, were not observed. 22,26 The Raman spectrum in Fig.…”

“…The Raman spectra of UO 2 (CO 3 ) 3 4− and CO 3 2− were obtained to confirm the existence of these species in the sample solutions. 21 Micro-Raman spectroscopy using an optical microscope (Olympus, BX43) and a Czerny-Turner-type spectrograph (Andor, SR-500) was performed in the present study. An Ar + laser (Coherent, Innova 70) at a wavelength of 514.5 nm was used as the light source.…”