Kinetics and Mechanism of RedOx Reactions of Np and Pu Ions with Several Organic Reductants

Koltunov, V. S.

doi:10.1080/00223131.2002.10875480

Cited by 17 publications

(18 citation statements)

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“…DISCUSSION OF THE REACTION SCHEME As one can see, the obtained kinetic equations (2) and (4) were similar: they had the first order with respect to the metal, the negative order with respect to the acid and fractional positive order with respect to the reductant. The found values of the carbohydrazide reaction orders differed from the data of the other studies on Pu(VI) and Np(VI) reduction with various organic hydrazine derivatives [3][4][5][6]. In most cases, the order of the reaction with respect to reducing agent was less than 1.…”

Section: The Interaction Of the Np(vi) With Carbohydrazidecontrasting

confidence: 55%

INTERACTION OF Pu(VI) AND Np(VI) WITH CARBOHYDRAZIDE IN NITRIC ACID SOLUTIONS

Zavalina¹,

Dvoeglazov²,

Pavlyukevich³

et al. 2017

RAD Conference Proceedings

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Abstract. The kinetics of Pu(VI) and Np(VI) recovery by carbohydrazide in an aqueous nitric acid solution was researched spectrophotometrically. Regarding to Pu(VI) it was established that in the interval of [HNO3] = 0.75-3.0 M and [CO(N2H3)2] = 0.1-0.4 M, the reaction rate was proportional to the concentration of Pu(VI). The reaction order with respect to carbohydrazide was determined to be 2.3, and -3 to nitric acid. The found activation energy of the reaction was 111 kJ·mol −1 . Regarding Np(VI), it was found that in the interval of [HNO3] = 0.75-3.0 M and [CO(N2H3)2] = 0.03-0.12 M, the reaction rate was proportional to the Np(VI) concentration. Reaction order with respect to carbohydrazide was determined to be 1.15, and -1.35 with respect to nitric acid. The found activation energy of the reaction was 85 kJ·mol −1 . Based on this kinetic data, a possible fundamental reaction mechanism was theorized.

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Section: The Interaction Of the Np(vi) With Carbohydrazidecontrasting

confidence: 55%

INTERACTION OF Pu(VI) AND Np(VI) WITH CARBOHYDRAZIDE IN NITRIC ACID SOLUTIONS

Zavalina¹,

Dvoeglazov²,

Pavlyukevich³

et al. 2017

RAD Conference Proceedings

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“…14,22 These results indicate that the different substituents of hydrazine can not only affect the energy barrier but also change the rate-determining step for their redox reaction. Pathway III of the second stage needs to overcome the 2.26 kcal/mol energy barrier, which is lower than pathways I and II, which are probably contributed by different natural charges on the H atom between the free radical and the free radical ion and the hydrogen bond between N1 and H w .…”

mentioning

confidence: 91%

“…Additionally, Koltunov investigated the kinetics of Np(VI) reduction with butanal oxime (C 3 H 7 CHNOH) and acetaldoxime (CH 3 CHNOH) and concluded that the reduction reactions are first-order and inhibited by H + ions. 21 The reduction reactions of Np(VI) with hydrazine and its hydrazine derivatives have been investigated, such as conditions, mechanism, and kinetics, 14,22,29,30 which demonstrate that hydrazine and its derivatives merely reduce Np(VI) to Np(V) without reducing U(VI) and Pu(IV) under certain conditions. We have theoretically investigated the reduction reaction of Np(VI) with hydrazine 31 hydroxyethyl hydrazine, methyl hydrazine, and formyl hydrazine), 32 and the calculated trend of their reduction ability is in good agreement with experimental observation.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, previous works showed that phenylhydrazine exhibits better reduction ability for Np(VI) compared to other hydrazine derivatives. 14,22 However, the reduction mechanism of Np(VI) with phenylhydrazine is not yet known. It is essential to elucidate the reaction mechanism of Np(VI) with phenylhydrazine employing theoretical calculations.…”

Section: Introductionmentioning

confidence: 99%

“…For Advanced PUREX (Plutonium Uranium Reduction EXtraction) − and SUPERPUREX, the Np separation can be achieved in the PUREX process according to the extraction difference of tributyl phosphate (TBP) for three oxidation states (Np(VI) > Np(IV) ≫ Np(V)). Some highly efficient and green free-salt reductants have been studied to reduce Np(VI) in the experiment such as aldehydes, − hydroxylamine, − oximes, , hydrazine, − and their derivatives. Reduction of Np(VI) by butyraldehyde isomers had been studied in nitric acid solution and demonstrated that iso -butyraldehyde has a higher reduction rate than n -butyraldehyde, reflecting that the structures of the isomers affect the reduction ability of Np(VI) .…”

Section: Introductionmentioning

confidence: 99%

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Theoretical Insights into the Reduction Mechanism of Np(VI) with Phenylhydrazine

Wang

et al. 2021

J. Phys. Chem. A

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Effectively adjusting and controlling the valence state of neptunium from the spent fuel reprocessing process is essential to separating neptunium. Hydrazine and its derivatives as free-salt reductants have been experimentally demonstrated to effectively reduce Np(VI) to Np(V). We have theoretically investigated the reduction mechanisms of Np(VI) with hydrazine and three derivatives (HOC2H4N2H3, CH3N2H3, and CHON2H3) in previous works. Herein, we further explored the reduction reaction of Np(VI) with phenylhydrazine (C6H5N2H3) including the free radical ion mechanism and the free radical mechanism. Potential energy profiles (PEPs) indicate that the rate-determining step of both mechanisms is the first stage. Moreover, for the free radical ion mechanism, phenylhydrazine possesses better reduction ability to Np(VI) compared to HOC2H4N2H3, CH3N2H3, and CHON2H3, which falls completely in line with the experimental results. Additionally, the analyses of the quantum theory of atoms in molecules (QTAIM), natural bond orbitals (NBOs), electron localization function (ELF), and localized molecular orbitals (LMOs) have been put forward to elucidate the bonding evolution for the structures of the reaction pathways. This work offers insights into the reduction mechanism of Np(VI) with phenylhydrazine from the theory point of view and contributes to design more high-efficiency reductants for the separation of U/Np and Np/Pu in spent fuel reprocessing.

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