Pulse radiolysis study on the reactivity of NO<sub>3</sub>˙ radical toward uranous(<scp>iv</scp>), hydrazinium nitrate and hydroxyl ammonium nitrate at room temperature and at 45 °C

Choe

et al. 2021

JACS Au

NO 3 • can compete with omnipotent • OH/SO 4 •– in decomposing aqueous pollutants because of its lengthy lifespan and significant tolerance to background scavengers present in H 2 O matrices, albeit with moderate oxidizing power. The generation of NO 3 • , however, is of grand demand due to the need of NO 2 • /O 3 , radioactive element, or NaNO 3 /HNO 3 in the presence of highly energized electron/light. This study has pioneered a singular pathway used to radicalize surface NO 3 – functionalities anchored on polymorphic α-/γ-MnO 2 surfaces (α-/γ-MnO 2 -N), in which Lewis acidic Mn 2+/3+ and NO 3 – served to form • OH via H 2 O 2 dissection and NO 3 • via radical transfer from • OH to NO 3 – ( • OH → NO 3 • ), respectively. The elementary steps proposed for the • OH → NO 3 • route could be energetically favorable and marginal except for two stages such as endothermic • OH desorption and exothermic • OH-mediated NO 3 – radicalization, as verified by EPR spectroscopy experiments and DFT calculations. The Lewis acidic strength of the Mn 2+/3+ species innate to α-MnO 2 -N was the smallest among those inherent to α-/β-/γ-MnO 2 and α-/γ-MnO 2 -N. Hence, α-MnO 2 -N prompted the rate-determining stage of the • OH → NO 3 • route ( • OH desorption) in the most efficient manner, as also evidenced by the analysis on the energy barrier required to proceed with the • OH → NO 3 • route. Meanwhile, XANES and in situ DRIFT spectroscopy experiments corroborated that α-MnO 2 -N provided a larger concentration of surface NO 3 – species with bi -dentate binding arrays than γ-MnO 2 -N. Hence, α-MnO 2 -N could outperform γ-MnO 2 -N in improving the collision frequency between • OH and NO 3 – species and in facilitating the exothermic transition of NO 3 – functiona...

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Deciphering Evolution Pathway of Supported NO₃^• Enabled via Radical Transfer from ^•OH to Surface NO₃^– Functionality for Oxidative Degradation of Aqueous Contaminants

Choe

et al. 2021

JACS Au

“…In cases where it is of interest to minimize the NO x gases produced, a knowledge of the mechanism is critical in developing appropriate minimization strategies. Mechanistic knowledge of the products produced during metal dissolution in nitric acid is also relevant to studying the radiolytic degradation of solvent in spent nuclear fuels as these products can have properties that hinder the reprocessing process or cause the corrosion of high-level waste storage containers. , …”

Section: Introductionmentioning

confidence: 99%

“…Mechanistic knowledge of the products produced during metal dissolution in nitric acid is also relevant to studying the radiolytic degradation of solvent in spent nuclear fuels as these products can have properties that hinder the reprocessing process or cause the corrosion of high-level waste storage containers. 5,6 While the dissolution of copper by nitric acid is well-known, there has been much debate as to the exact reactions that control the dissolution process and what controls the concentration dependence of the reaction. A proper description of the dissolution process is critical to predicting and understanding the origin of the NO x products as a function of experimental conditions, such as acid concentration.…”

Section: ■ Introductionmentioning

confidence: 99%

Mechanistic Study of the Production of NO_x Gases from the Reaction of Copper with Nitric Acid

et al. 2020

Copper dissolution in nitric acid is a historic reaction playing a central role in many industrial processes, particularly for metal recovery from the electronics to nuclear industries. The mechanism through which this process occurs is debated. In order to better understand this process, quantum chemical calculations were performed to elucidate the key steps in the mechanism of copper dissolution in nitric acid. We combine both Kohn–Sham density functional theory and ab initio molecular dynamics simulations to understand the mechanism of the formation of the key products: NO2, HNO2, and NO. Our calculations suggest that the mechanisms of formation of NO2, HNO2, and NO are interconnected.

Radiation‐Induced Defects in Uranyl Trinitrate Solids

Kruse,

Rajapaksha,

LaVerne

et al. 2024

Chemistry A European J

Actinides are inherently radioactive; thus, ionizing radiation is emitted by these elements can have profound effects on its surrounding chemical environment through the formation of free radical species. While previous work has noted that the presence of free radicals in the system impacts the redox state of the actinides, there is little atomistic understanding of how these metal cations interact with free radicals. Herein, we explore the effects of radiation (UV and γ) on three U(VI) trinitrate complexes, M[UO2(NO3)3] (where M = K+, Rb+, Cs+), and their respective nitrate salts in the solid state via electron paramagnetic resonance (EPR) and Raman spectroscopy paired with Density Functional Theory (DFT) methods. We find that the alkali salts form nitrate radicals under UV and γ irradiation, but also note the presence of additional degradation products. M[UO2(NO3)3] solids also form nitrate radicals and additional DFT calculations indicate the species corresponds to a change from the bidentate bound nitrate anion into a monodentate NO3• radical. Computational studies also highlight the need to include the second sphere coordination environment around the [UO2(NO3)3]0,1 species to gain agreement between the experimental and predicted EPR signatures.