A preliminary study of the hydrolysis of hydroxamic acid complexants in the presence of oxidising metal ions

Andrieux, Fabrice; Boxall, Colin; May, Iain; Taylor, Robin

doi:10.1088/1757-899x/9/1/012081

Cited by 3 publications

(9 citation statements)

References 10 publications

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“…This is represented experimentally by the end of the induction period and the appearance of Pu(III) in solution as the 'free' Pu(IV) is rapidly reduced either by the hydroxylamine formed from XHA hydrolysis or the hydroxamic acid itself. A full kinetic analysis of the AHA data has now been completed and will be reported separately [28] but it is sufficient to note here that the detailed treatment is generally consistent with the overall scheme described herein.…”

Section: Discussionmentioning

confidence: 81%

Section: Discussionmentioning

confidence: 94%

“…Preliminary speciation diagram calculations indicate that, at 0.008 M total AHA, Pu(IV) exists predominantly as the 1 : 1 Pu : AHA complex at 1 M HNO 3 [28]. In the same system at 0.1 M HNO 3 , Pu(IV) exists as a mix of the 1 : 1 and 1 : 2 Pu : AHA complexes with the 1 : 1 complex being approximately twice the concentration of the 1 : 2 complex [28]. By use of those equilibrium constants for formation of the 1 : 1 and 1 : 2 Pu(IV) : AHA species in nitric acid derived from stability constant measurements in HClO 4 [12] and Pu(IV) nitrate complexation constants [31], it is possible through use of Eq.…”

Section: Discussionmentioning

confidence: 97%

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Oxidation–reduction reactions of simple hydroxamic acids and plutonium(IV) ions in nitric acid

Carrott¹,

Fox²,

LeGurun³

et al. 2008

Radiochimica Acta

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SummarySimple hydroxamic acids such as formo- and aceto-hydroxamic acids have been proposed as suitable reagents for the separation of either Pu and/or Np from U in modified or single cycle Purex based solvent extraction processes designed to meet the emerging requirements of advanced fuel cycles. The stability of these hydroxamic acids is dominated by their decomposition through acid hydrolysis. Kinetic studies of the acid hydrolysis of formo- and aceto-hydroxamic acids are reported in the absence and the presence of Pu(IV) ions. The slow reduction of these plutonium(IV) hydroxamate complexes to Pu(III) aquo-ions has been characterised by spectrophotometry and cyclic voltammetry. The reductions of Pu(IV) in the presence of FHA and AHA are consistent with a mechanism in which free hydroxamic acid in solution is hydrolysed whilst Pu(IV) ions remain fully complexed to hydroxamate ligands; then at some point close to a 1 : 1 Pu(IV) : XHA ratio, some free Pu

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Section: Discussionmentioning

confidence: 81%

Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 97%

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Oxidation–reduction reactions of simple hydroxamic acids and plutonium(IV) ions in nitric acid

Carrott¹,

Fox²,

LeGurun³

et al. 2008

Radiochimica Acta

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“…18,19 The majority of reactions involving actinides and AHA have been studied in advanced PUREX separation processes, which utilize high concentrations of nitric acid (1−4 M) with actinides at mM concentrations. 12,19,20 In acidic solutions AHA undergoes hydrolysis reactions (Figure 1b), leading to the formation of hydroxylamine and the reduction of Pu(IV) to Pu(III). These studies reveal that the reduction of Pu(VI) and Np(VI) occurs by a rapid electron exchange with AHA (Figure 1c) followed by a slow continued reduction from acid hydrolysis products (hydroxylamine).…”

Section: ■ Introductionmentioning

confidence: 99%

“…These studies reveal that the reduction of Pu(VI) and Np(VI) occurs by a rapid electron exchange with AHA (Figure 1c) followed by a slow continued reduction from acid hydrolysis products (hydroxylamine). 12,20,21 The formation of an AHA−metal ligand has variable effects on hydrolysis rates with Fe(III)− AHA ligands increasing the hydrolysis rates while Np(IV)− AHA decreases the rate. 10,11,22,23 The reactions of Pu−AHA ligands at an environmentally relevant pH (5−8) have not yet been investigated and may play a role in the fate of actinides complexed by siderophore breakdown products (mono and dihydroxamates) at contamination sites.…”

Section: ■ Introductionmentioning

confidence: 99%

Reduction of Plutonium(VI) to (V) by Hydroxamate Compounds at Environmentally Relevant pH

Morrison

Jiao

Kersting

et al. 2018

Environ. Sci. Technol.

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Natural organic matter is known to influence the mobility of plutonium (Pu) in the environment via complexation and reduction mechanisms. Hydroxamate siderophores have been specifically implicated due to their strong association with Pu. Hydroxamate siderophores can also break down into di and monohydroxamates and may influence the Pu oxidation state, and thereby its mobility. In this study we explored the reactions of Pu(VI) and Pu(V) with a monohydroxamate compound (acetohydroxamic acid, AHA) and a trihydroxamate siderophore desferrioxamine B (DFOB) at an environmentally relevant pH (5.5-8.2). Pu(VI) was instantaneously reduced to Pu(V) upon reaction with AHA. The presence of hydroxylamine was not observed at these pHs; however, AHA was consumed during the reaction. This suggests that the reduction of Pu(VI) to Pu(V) by AHA is facilitated by a direct one electron transfer. Importantly, further reduction to Pu(IV) or Pu(III) was not observed, even with excess AHA. We believe that further reduction of Pu(V) did not occur because Pu(V) does not form a strong complex with hydroxamate compounds at a circum-neutral pH. Experiments performed using desferrioxamine B (DFOB) yielded similar results. Broadly, this suggests that Pu(V) reduction to Pu(IV) in the presence of natural organic matter is not facilitated by hydroxamate functional groups and that other natural organic matter moieties likely play a more prominent role.

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Cr(VI) Reduction by Siderophore Alone and in Combination with Reduced Clay Minerals

Zhang

Guo

et al. 2022

Environ. Sci. Technol.

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Siderophores and iron-containing clays are known to influence the transformation of chromium in the environment. The role of clays in hexavalent chromium [Cr(VI)] reduction has been reported extensively. However, the mechanisms of Cr(VI) reduction by siderophores and their combination with iron-bearing clays are poorly known. Herein, we report the kinetics and products of Cr(VI) reduction by a siderophore alone or in combination with reduced clays. Results showed that Cr(VI) reduction by a tri-hydroxamate siderophore�desferrioxamine B (DFOB)�at a pH of 6 was achieved by one-electron transfer via the formation of Cr(V) intermediate. The formed Cr(V) was further reduced to organically complexed Cr(III). The Cr(VI) reduction rate and extent in the presence of both DFOB and reduced clays unexpectedly decreased relative to that with reduced clays alone, despite both serving as Cr(VI) reductants. The interaction between DFOB and clays (e.g., adsorption/intercalation, dissolution, and/or oxidation) was primarily responsible for Cr(VI) reduction inhibition. The extent of inhibition increased at higher DFOB concentrations in the presence of iron-rich nontronite but decreased in the presence of iron-poor montmorillonite, which may be related to their different Cr(VI) reduction mechanisms. This study highlights the importance of siderophores in chromium transformation and its impact on the reactivity of iron-bearing clays toward heavy metal reduction in the environment.

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A preliminary study of the hydrolysis of hydroxamic acid complexants in the presence of oxidising metal ions

Cited by 3 publications

References 10 publications

Oxidation–reduction reactions of simple hydroxamic acids and plutonium(IV) ions in nitric acid

Oxidation–reduction reactions of simple hydroxamic acids and plutonium(IV) ions in nitric acid

Reduction of Plutonium(VI) to (V) by Hydroxamate Compounds at Environmentally Relevant pH

Cr(VI) Reduction by Siderophore Alone and in Combination with Reduced Clay Minerals

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