Pu(V) and Pu(IV) Sorption to Montmorillonite

Begg, James D.; Zavarin, Mavrik; Zhao, Pihong; Tumey, Scott J.; Powell, Brian A.; Kersting, Annie B.

doi:10.1021/es305257s

Cited by 67 publications

(116 citation statements)

References 54 publications

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“…The Fe(II)/Fe(III) redox couple can stabilize the oxidation state of Pu, since Fe(II) typically oxidizes before Pu(IV), while Fe(III) is typically reduced before Pu(IV). This couple also affects environmental Pu transport mechanisms, since Pu(IV) is relatively insoluble in water, but forms PuO 2 colloids [9,10] and sorbs to colloidal minerals [79][80][81]. The encasement of Pu into macroscale glassy matrices, however, may reduce the probability of initial colloid formation, and serve to inhibit the transport of actinides, as observed in waste vitrification studies.…”

Section: To Fe(iii) and Corresponding U(vi) Reduction To U(iv) It Imentioning

confidence: 99%

Chemical speciation of U, Fe, and Pu in melt glass from nuclear weapons testing

Pacold

Lukens

Booth

et al. 2016

Journal of Applied Physics

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Nuclear weapons testing generates large volumes of glassy material that influence the transport of dispersed actinides in the environment and may carry information on the composition of the detonated device. We determine the oxidation state of U and Fe (which is known to buffer the oxidation state of actinide elements and to affect the redox state of groundwater) in samples of melt glass collected from three U.S. nuclear weapons tests. For selected samples, we also determine the coordination geometry of U and Fe, and we report the oxidation state of Pu from one melt glass sample. We find significant variations among the melt glass samples, and in particular, find a clear deviation in one sample from the expected buffering effect of Fe(II)/Fe(III) on the oxidation state of uranium. In the first direct measurement of Pu oxidation state in a nuclear test melt glass, we obtain a result consistent with existing literature that proposes Pu is primarily present as Pu(IV) in post-detonation material. In addition, our measurements imply that highly mobile U(VI) may be produced in significant quantities when melt glass is quenched rapidly following a nuclear detonation, though these products may remain immobile in the vitrified matrices. The observed differences in chemical state among the three samples show that redox conditions can vary dramatically across different nuclear test conditions. The local soil composition, associated device materials, and the rate of quenching are all likely to affect the final redox state of the glass. The resulting variations in glass chemistry are significant for understanding and interpreting debris chemistry, and the later environmental mobility of dispersed material.

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Section: To Fe(iii) and Corresponding U(vi) Reduction To U(iv) It Imentioning

confidence: 99%

Chemical speciation of U, Fe, and Pu in melt glass from nuclear weapons testing

Pacold

Lukens

Booth

et al. 2016

Journal of Applied Physics

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“…The affinity of Pu(IV) to mineral surfaces is substantially greater than that of Pu(V), and this has been attributed to their difference in effective charge (11). However, it has been shown that Pu(V) can be reduced to Pu(IV) and even Pu(III) on a range of mineral surfaces, leading to a congruence in the apparent sorption behavior of Pu(IV) and Pu(V) (5). At high concentrations (Ͼ10 Ϫ8 Ϯ 1 M), Pu(IV) hydrolyzes to form Pu(IV) oxide precipitates (4,12).…”

mentioning

confidence: 99%

Interactions of Plutonium with Pseudomonas sp. Strain EPS-1W and Its Extracellular Polymeric Substances

Boggs

Jiao

Dai

et al. 2016

Appl Environ Microbiol

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Safe and effective nuclear waste disposal, as well as accidental radionuclide releases, necessitates our understanding of the fate of radionuclides in the environment, including their interaction with microorganisms. We examined the sorption of Pu(IV) and Pu(V) to Pseudomonas sp. strain EPS-1W, an aerobic bacterium isolated from plutonium (Pu)-contaminated groundwater collected in the United States at the Nevada National Security Site (NNSS) in Nevada. We compared Pu sorption to cells with and without bound extracellular polymeric substances (EPS). Wild-type cells with intact EPS sorbed Pu(V) more effectively than cells with EPS removed. In contrast, cells with and without EPS showed the same sorption affinity for Pu(IV). In vitro experiments with extracted EPS revealed rapid reduction of Pu(V) to Pu(IV). Transmission electron microscopy indicated that 2-to 3-nm nanocrystalline Pu(IV)O 2 formed on cells equilibrated with high concentrations of Pu(IV) but not Pu(V). Thus, EPS, while facilitating Pu(V) reduction, inhibit the formation of nanocrystalline Pu(IV) precipitates. IMPORTANCEOur results indicate that EPS are an effective reductant for Pu(V) and sorbent for Pu(IV) and may impact Pu redox cycling and mobility in the environment. Additionally, the resulting Pu morphology associated with EPS will depend on the concentration and initial Pu oxidation state. While our results are not directly applicable to the Pu transport situation at the NNSS, the results suggest that, in general, stationary microorganisms and biofilms will tend to limit the migration of Pu and provide an important Pu retardation mechanism in the environment. In a broader sense, our results, along with a growing body of literature, highlight the important role of microorganisms as producers of redox-active organic ligands and therefore as modulators of radionuclide redox transformations and complexation in the subsurface.T he civil production of nuclear energy and military production of nuclear materials have resulted in an estimated worldwide inventory of over 2,000 metric tons of plutonium (Pu) (1). This inventory continues to increase at a rate of approximately 70 metric tons per year as a result of global nuclear energy production (2). Due to its long half-life (24,100 years for 239 Pu) and high radiotoxicity (3), Pu is an important driver in public health risk assessments for nuclear waste repositories and radiologically contaminated sites. However, predicting how Pu behaves in the environment and ultimately calculating its human health risk are limited by our understanding of the dominant biogeochemical processes controlling its behavior.The behavior of Pu in the environment is strongly dependent on its oxidation state and concentration. Among all the actinides, Pu has one of the most complex chemical, redox, and surface sorption behaviors. At low concentrations, Pu can exist as aqueous species in the III, IV, V, and/or VI oxidation states, all of which have different solubilities (4), mineral sorption affinities (5-7), and hence...

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“…Many studies argued that Pu(V) aq has weak affinity for mineral surfaces (an implication of higher mobilization). An interpretation that slow reduction of Pu(V) aq to Pu(IV) aq , which has a higher tendency to complex with ≡X-OH sites (X = Al, Fe, and Mn), was usually given (Roberts et al, 2008;Begg et al, 2013;Powell et al, 2014). Instead, much lower mobilization of Pu(V) aq was observed in our transport experiments.…”

Section: Accepted Manuscriptmentioning

confidence: 55%