Photoreduction of uranyl ion in aqueous solution. I. With ethanol in sulphuric acid solutions

Nagaishi, Ryuji; Katsumura, Yosuke; Ishigure, Kenkichi; Aoyagi, Hisao; Yoshida, Zenko; Kimura, Takaumi

doi:10.1016/1010-6030(95)04272-5

Cited by 21 publications

(13 citation statements)

References 30 publications

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“…The electronic excitation can be quenched by various organic molecules through hydrogen-atom ( • H) transfer to the *[UO 2 ] 2+ unit, saturating the °O ax hole, thereby leaving [|O⟩ • U⟨OH] 2+ and yielding some organic radicals. This process may be baptized “hole-driven hydrogen transfer” (HDHT), the new relative of common “proton-coupled electron transfer” (PCET). − ,,,− The HDHT is also called “light-driven oxyl formation causing H-abstraction and substrate oxidation” . In aqueous solution, two • U +5 species can spontaneously disproportionate to a pair of •• U +4 and U +6 . ,, The reduced [OU +5 O] 1+ unit can also be directly oxidized to [OU +6 O] 2+ in the presence of oxygen, competing with the disproportionation. ,,, Concerning O 2 -involving reactions, dioxygen peroxide (O 2 –2 ) and superoxide ( • O 2 –1 ) anions and their conjugate acids have been suggested as intermediates in experimental works. ,,, …”

Section: Introductionmentioning

confidence: 99%

Excited-State Chemistry: Photocatalytic Methanol Oxidation by Uranyl@Zeolite through Oxygen-Centered Radicals

Zhang

Schwarz

et al. 2020

Inorg. Chem.

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We have elucidated the complex reaction network of partial methanol oxidation, H 3 COH + O 2 → H 2 CO + H 2 O 2 , at a visible-light-activated actinide photocatalyst. The reaction inertness of CH bonds and OO diradicals at ambient conditions is overcome through catalysis by photoexcited uranyl units (*UO 2 2+ ) anchored on a mesoporous silicate. The electronic ground-and excited-state energy hypersurfaces are investigated with quasirelativistic density-functional and ab initio correlated wave function approaches. Our study suggests that the molecular cluster can react on the excited energy surface due to the longevity of excited uranyl, typical for f-element compounds. The theoretically predicted energy profiles, chemical intermediates, related radicals, and product species are consistent with various experimental findings. The uranyl excitation opens various reaction pathways for the oxidation of volatile organic compounds (VOCs) by "hole-driven hydrogen transfer" (HDHT) through several exothermic steps over low activation barriers toward environmentally clean or chemically interesting products. Quantum-chemical modeling reveals the high efficiency of the uranyl photocatalysis and directs the way to further understanding and improvement of VOC degradation, chemical synthesis, and biologic photochemical interactions between uranyl and the environment.

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Section: Introductionmentioning

confidence: 99%

Excited-State Chemistry: Photocatalytic Methanol Oxidation by Uranyl@Zeolite through Oxygen-Centered Radicals

Zhang

Schwarz

et al. 2020

Inorg. Chem.

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“…However, the mechanism by which these cytochromes transfer electrons to U(VI) is unknown. U(V) is unstable as an aqueous complex (Nagaishi et al 1996), and it is therefore possible that enzymatic reduction proceeds from U(VI) to U(V), followed by disproportionation to U(IV) and U(VI). Tentative evidence in support of this mechanism has been provided by Renshaw et al (2005) and Grossmann et al (2007), but further work is required to unambiguously demonstrate the relevance of this reduction pathway.…”

Section: Biological Reduction and Uraninite Precipitationmentioning

confidence: 99%

Biogenic Uraninite Nanoparticles and Their Importance for Uranium Remediation

et al. 2008

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Biogenic uraninite is of interest to geoscientists for its importance to bioremediation strategies, remarkably small particle size, and biological origin. Recent studies have begun to illuminate the chemical/structural complexities of this important natural nanomaterial. Intriguingly, in spite of its incredibly diminutive size, the molecular-scale structure, energetics, and surfacearea-normalized dissolution rates of hydrated biogenic uraninite appear to be similar to those of coarser-particle, abiotic, stoichiometric UO 2 . These findings have important implications for the role of size as a moderator of nanoparticle aqueous reactivity and for the bioremediation of subsurface U(VI) contamination.

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“…The residue obtained was dissolved in 1 Μ H 2 S0 4 to yield U(VI) stock solution. Uranium(IV) solution was prepared just before the measurement from 0.02 Μ U(VI) in 1 Μ H 2 S0 4 by photochemical reduction using excess amount (0.28 M) of ethanol as a reducing agent for U(VI) and UV light from a high pressure mercury lamp(100 W) [14]. The photoreduction was completed in three hours as monitored by a spectrophotometer (Shimadzu, UV-3100PC).…”

Section: Methodsmentioning

confidence: 99%

Laser-Induced Photothermal Displacement Spectroscopy (LIPDS) for Speciation of Lanthanides and Actinides

1998

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We have developed a novel photothermal spectroscopy, named Laser-Induced Photothermal Displacement Spectroscopy (LIPDS), having characteristics of high sensitivity, non-contact detection, remote and easy operation by using an optical heterodyne interferometer as a detection tool. The LIPDS system was constructed using a Nd:YAG laser pumped tunable dye laser and an interferometer. Optimal conditions for the measurement have been studied using lanthanide and actinide ions. By experiments, it was verified that the principle of LIPDS is based on the following processes: generation of an acoustic wave by absorption of light, vibration of a sample cell induced by propagation and reflection of the acoustic wave, and detection of the vibrational displacement of the cell by an optical heterodyne interferometer. For demonstration absorption spectra of different metal ions in aqueous solution were measured by the system. The LIPDS system is applicable for quantitative detection and speciation of the ions with the detection limit of absorptivity down to 3X10" 4 cm"'.

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Photoreduction of uranyl ion in aqueous solution. I. With ethanol in sulphuric acid solutions

Cited by 21 publications

References 30 publications

Excited-State Chemistry: Photocatalytic Methanol Oxidation by Uranyl@Zeolite through Oxygen-Centered Radicals

Excited-State Chemistry: Photocatalytic Methanol Oxidation by Uranyl@Zeolite through Oxygen-Centered Radicals

Biogenic Uraninite Nanoparticles and Their Importance for Uranium Remediation

Laser-Induced Photothermal Displacement Spectroscopy (LIPDS) for Speciation of Lanthanides and Actinides

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