A Kinetic Study of the Reduction of Neptunium(VI) by Hydrogen Peroxide<sup>1</sup>

Zielen, A.J.; Sullivan, James C.; Cohen, Donald S.; Hindman, J. C.

doi:10.1021/ja01554a012

Cited by 20 publications

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“…Studies of systems containing Np(V) and H 2 O 2 are limited. Oxidation of Np(III) and Np(IV) by hydrogen peroxide has been observed, , and studies of Np(VI) interaction with H 2 O 2 mostly indicate that Np(VI) is reduced to Np(V), and some Np(IV) is produced at high H 2 O 2 concentrations. , One study postulated the formation of a Np(VI) peroxo complex in alkaline conditions on the basis of reaction rates. , A study of Np(V) in solutions containing NaHCO 3 and H 2 O 2 indicated Np(V) was oxidized to Np(VI) . As observed for 1 , Np(V/VI) 24 clusters formed when hydroxide base and excess H 2 O 2 were added to a Np(V) stock solution.…”

Section: Resultsmentioning

confidence: 99%

Neptunyl Peroxide Chemistry: Synthesis and Spectroscopic Characterization of a Neptunyl Triperoxide Compound, Ca₂[NpO₂(O₂)₃]·9H₂O

et al. 2019

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Little is known about the crystal chemistry of neptunyl peroxide compounds compared to uranyl peroxide compounds, for which dozens of structures have been described. Uranyl peroxides are formed over a broad range of pH and solution conditions, but neptunyl peroxide chemistry is complicated by the ability of H 2 O 2 to act as an oxidizing or reducing agent for Np, depending on the conditions present. The combination of Np(V) in 1 M HCl, H 2 O 2 , and CaCl 2 under alkaline conditions leads to the immediate crystallization of a neptunyl triperoxide monomer, Ca 2 [NpO 2 (O 2 ) 3 ]•9H 2 O, which is the first Np(VI)-based peroxide compound to be characterized in the solid state and is isostructural to Ca 2 [UO 2 (O 2 ) 3 ]•9H 2 O. The crystal structure reveals bond distances of 1.842(7) Å that are the longest reported to date for nonbridging Np(VI)-O yl bonds. Computational studies probe the oxidation state and bond distances of the monomer unit and differences in Raman spectra of the neptunyl and uranyl triperoxide compounds.

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Section: Resultsmentioning

confidence: 99%

Neptunyl Peroxide Chemistry: Synthesis and Spectroscopic Characterization of a Neptunyl Triperoxide Compound, Ca₂[NpO₂(O₂)₃]·9H₂O

et al. 2019

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“…As shown in Fig. 8, all Np(VI) is first reduced to Np(V), which can be explained by the reaction with H 2 O 2 (13,14). …”

Section: Effect Of High Concentrations Of Methylurea On the Redox Spementioning

confidence: 86%

Effect of Gamma Irradiation on the Oxidation State of Neptunium in Nitric Acid in the Presence of Selected Scavengers

Přeček

Paulenová

Tkáč

et al. 2010

Separation Science and Technology

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A series of experiments was performed with selected reagents that were added to inhibit the reduction of Np(VI) to Np(V) during irradiation of its solutions in HNO 3 . Acetamide and methylurea as nitrous acid scavengers, and vanadium(V) as a neptunium(V) oxidizer, were examined in this effort. Solutions of these reagents in 4 M HNO 3 were irradiated in a Co-60 gamma irradiator. Additions of 1-10 mM of methylurea and vanadium(V) essentially had no effect on the final oxidation state of Np after irradiation with a dose of 60 kGy, while the addition of higher concentrations of methylurea (50 and 100 mM) led to an almost complete reduction of Np to the tetravalent oxidation state.

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“…The solubility has a minimum at 1.5-2 M HNO 3 [10]. 2 mol of Np(V) is formed per mole of Н 2 О 2 , i.e., the reaction is described by the equation (18) …”

Section: Reactions With O 2 and H 2 Omentioning

confidence: 99%

“…Addition of Н 2 О 2 to a Np(IV) solution leads to the formation of a Np(IV) peroxide complex, and its addition to a Np(III) + Np(IV) mixture in 1 and 0.1 M HClO 4 , to accumulation of Np(V) (from 14 to 78%). Burgener and Sullivan [4] suggest the occurrence of the reactions DOI: 10.1134/S1066362212030034…”

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confidence: 99%

Effect of O2, H2O2, and HNO2 on the stability of Np(III–VII) in aqueous solutions

et al. 2012

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Published data on reactions of Np ions with О 2 , Н 2 О 2 , HNO 2 , and HNO 3 in solutions of various compositions in a wide pH range are considered. О 2 oxidizes Np(III) in acid solution and Np(IV) and Np(V) in alkaline solutions. Н 2 О 2 exhibits dual behavior. In weakly acidic solutions, it converts Np(III) and (IV) to Np(V), in 0.75-1 M NaHCO 3 it oxidizes Np(V) to Np(VI), whereas in dilute HClO 4 and HNO 3 and in carbonate and alkali solutions it reduces Np(VI), and in alkali solutions it reduces Np(VII). The first step of reduction in most cases is the formation of the Np(VI) peroxide complex, and the next step is the intramolecular charge transfer. In concentrated HNO 3 solutions, H 2 O 2 converts Np(V) to Np(IV) and Np(VI) and then reduces Np(VI). Some radiation-, photo-, and sonochemical reactions occur via formation of excimers, i.e., of dimers arising from excited and unexcited Np ions. The excimer decomposes into two ions with higher and lower oxidation states. In reduction reactions, the excimer eliminates Н 2 О 2 (in addition to the Н 2 О 2 arising as primary product of water radiolysis). In HNO 3 solutions, oxidation of Np ions occurs only in the presence of HNO 2 arising as reaction product or upon radiolysis, photolysis, or sonolysis. The active species are NO 2 -, NO 2 , and NO + present in equilibrium with HNO 2 .Any solutions contacting with air contain О 2 . The Np ions whose oxidation potential is lower than the О 2 /Н 2 О potential in the given medium react with О 2 . Hydrogen peroxide is formed in solutions containing actinides and fission products under the action of α-, β-, and γ-radiation, and HNO 2 is formed in HNO 3 solutions. Solutions of HNO 3 , Н 2 О 2 , and HNO 2 are used in processes for Np recovery and purification, and also in laboratory practice. In this connection, we analyze here the published data on reactions of Np(III-VII) ions with О 2 , Н 2 О 2 , HNO 2 , and HNO 3 . In reviews [1-3] these reactions are not considered.At the same time, in a 0.01 M HClO 4 solution saturated with О 2 , the Np(IV) concentration decreased from 9.81 × 10 -4 to 5.92 × 10 -4 M in 16 h at 25°С. We estimate the bimolecular rate constants of the reactions of О 2 with Np(III) and Np(IV) at 3.5 × 10 2 and 8.8 × 10 -3 l mol -1 s -1 , respectively.

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A Kinetic Study of the Reduction of Neptunium(VI) by Hydrogen Peroxide¹

Cited by 20 publications

References 2 publications

Neptunyl Peroxide Chemistry: Synthesis and Spectroscopic Characterization of a Neptunyl Triperoxide Compound, Ca₂[NpO₂(O₂)₃]·9H₂O

Neptunyl Peroxide Chemistry: Synthesis and Spectroscopic Characterization of a Neptunyl Triperoxide Compound, Ca₂[NpO₂(O₂)₃]·9H₂O

Effect of Gamma Irradiation on the Oxidation State of Neptunium in Nitric Acid in the Presence of Selected Scavengers

Effect of O2, H2O2, and HNO2 on the stability of Np(III–VII) in aqueous solutions

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A Kinetic Study of the Reduction of Neptunium(VI) by Hydrogen Peroxide1

Cited by 20 publications

References 2 publications

Neptunyl Peroxide Chemistry: Synthesis and Spectroscopic Characterization of a Neptunyl Triperoxide Compound, Ca2[NpO2(O2)3]·9H2O

Neptunyl Peroxide Chemistry: Synthesis and Spectroscopic Characterization of a Neptunyl Triperoxide Compound, Ca2[NpO2(O2)3]·9H2O

Effect of Gamma Irradiation on the Oxidation State of Neptunium in Nitric Acid in the Presence of Selected Scavengers

Effect of O2, H2O2, and HNO2 on the stability of Np(III–VII) in aqueous solutions

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A Kinetic Study of the Reduction of Neptunium(VI) by Hydrogen Peroxide¹

Neptunyl Peroxide Chemistry: Synthesis and Spectroscopic Characterization of a Neptunyl Triperoxide Compound, Ca₂[NpO₂(O₂)₃]·9H₂O

Neptunyl Peroxide Chemistry: Synthesis and Spectroscopic Characterization of a Neptunyl Triperoxide Compound, Ca₂[NpO₂(O₂)₃]·9H₂O