Insights into the Mechanism of Neptunium Oxidation to the Heptavalent State

Dmytro Kravchuk; Logan J Augustine; Harindu Rajapaksha; Grant Benthin; Enrique R. Batista; Ping Yang; Tori Forbes

doi:10.1002/chem.202304049

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Insights into the Mechanism of Neptunium Oxidation to the Heptavalent State

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Insights into the Mechanism of Neptunium Oxidation to the Heptavalent State

Dmytro Kravchuk, Logan J Augustine, Harindu Rajapaksha, Grant Benthin, Enrique R. Batista, Ping Yang and Tori Forbes

Chemistry : a European journal, Vol.30(23), e202304049

03/12/2024

DOI: 10.1002/chem.202304049

PMID: 38183632

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Abstract

Neptunium can exist in multiple oxidation states, including the rare and poorly understood heptavalent form. In this work, we monitored the formation of heptavalent neptunium [Np(VII)O4(OH)2]3‐ during ozonolysis of aqueous MOH (M = Li, Na, K) solutions using a combined experimental and theoretical approach. All experimental reactions were closely monitored via absorption and vibrational spectroscopy to follow both the oxidation state and the speciation of neptunium guided by the calculated vibrational frequencies for various neptunium species. The mechanism of the reaction partly involves oxidative dissolution of transient Np(VI) oxide/hydroxide solid phases, the identity of which are dependent on the co‐precipitating counter‐cation Li+/Na+/K+. Additional calculations suggest that the most favorable energetic pathway occurs through the reaction of a [Np(V)O2(OH)4]3‐ with the hydroxide radical to form [Np(VI)O2(OH)4]2‐, followed by an additional oxidation with HO● to create [Np(VII)O4(OH)2]3‐.

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Details

Title: Subtitle: Insights into the Mechanism of Neptunium Oxidation to the Heptavalent State
Creators: Dmytro Kravchuk - University of Iowa
Logan J Augustine - University of Iowa
Harindu Rajapaksha - University of Iowa
Grant Benthin - University of Iowa
Enrique R. Batista - Los Alamos National Laboratory
Ping Yang - Los Alamos National Laboratory
Tori Forbes - University of Iowa
Resource Type: Journal article
Publication Details: Chemistry : a European journal, Vol.30(23), e202304049
DOI: 10.1002/chem.202304049
PMID: 38183632
NLM abbreviation: Chemistry
ISSN: 0947-6539
eISSN: 1521-3765
Publisher: Wiley
Grant note: US Department of Energy. Grant Numbers: DE-SC0021420, DE-SC0014664, DE-AC52-06NA25396
Language: English
Electronic publication date: 01/06/2024
Date published: 03/12/2024
Academic Unit: Civil and Environmental Engineering; Core Research Facilities; Chemistry
Record Identifier: 9984544629102771

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