Oxidative dissolution of UO2 in a simulated groundwater containing synthetic nanocrystalline mackinawite

Bi, Yuqiang; Hyun, Sung Pil; Kukkadapu, Ravi; Hayes, Kim F.

doi:10.1016/j.gca.2012.10.032

Cited by 68 publications

(99 citation statements)

References 80 publications

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“…The results are noticeably different from the inhibited oxidative dissolution of UO 2 by FeS as discussed in previous studies. 22,23 The dissolution rate of synthetic UO 2 is approximately an order of magnitude lower in the presence of FeS under similar conditions due to effective removal of oxygen (Figure 2). Extensive dissolution of UO 2 occurred only when FeS was depleted and DO levels started to increase.…”

Section: ■ Results and Discussionmentioning

confidence: 94%

“…22 The precipitate was allowed to age for 3 days under constant stirring before being rinsed with deoxygenated DI water. The final product was freeze-dried under a vacuum and stored in capped glass vials inside the anaerobic chamber until use.…”

Section: Synthesis Of Mackinawite and Noncrystalline U(iv)mentioning

confidence: 99%

“…Therefore, it is plausible that the oxidation products of FeS catalyzed the oxidative mobilization of noncrystalline U(IV), given FeS can transform to a range of redox reactive Fe(III) species after oxidation. 22,29 To examine the potential of Fe(III) species for oxidizing noncrystalline U(IV), we determined effluent Fe(II) concentrations from flow-through experiments in the presence of FeS. As shown in previous studies, FeS dissolved under oxic conditions as a result of oxidative dissolution and preferential release of ferrous iron.…”

Section: Environmental Science and Technologymentioning

confidence: 99%

“…33,34 Depending on the solution pH, FeS oxidation also led to the formation of various Fe(III) (hydr)oxides, including ferrihydrite, goethite, lepidocrocite, and green rust. 22,29 If the Fe(III) species can react with noncrystalline U(IV), higher concentrations of dissolved Fe(II) would be generated relative to background Fe(II). With only FeS (Figure 3), a peak concentration for dissolved Fe(II) of ∼60 μM was rapidly established after ∼5 τ, which then continuously decreased until complete FeS oxidation.…”

Section: Environmental Science and Technologymentioning

confidence: 99%

“…11,18,19 Previous studies have conclusively demonstrated that FeS is capable of both reducing uranyl ion 20,21 and inhibiting UO 2 oxidative dissolution by scavenging DO. 22,23 Field studies attributed the retardation of U mobilization to sulfide minerals formed in the subsurface environment. 18,24 Because FeS was also found in close association with noncrystalline U(IV) in biostimulated aquifers, 11 the protection of the U(IV) species against oxidation was expected.…”

Section: ■ Introductionmentioning

confidence: 99%

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Rapid Mobilization of Noncrystalline U(IV) Coupled with FeS Oxidation

Stylo

Bernier‐Latmani

et al. 2016

Environ. Sci. Technol.

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The reactivity of disordered, noncrystalline U(IV) species remains poorly characterized despite their prevalence in biostimulated sediments. Because of the lack of crystalline structure, noncrystalline U(IV) may be susceptible to oxidative mobilization under oxic conditions. The present study investigated the mechanism and rate of oxidation of biogenic noncrystalline U(IV) by dissolved oxygen (DO) in the presence of mackinawite (FeS). Previously recognized as an effective reductant and oxygen scavenger, nanoparticulate FeS was evaluated for its role in influencing U release in a flowthrough system as a function of pH and carbonate concentration. The results demonstrated that noncrystalline U(IV) was more susceptible to oxidation than uraninite (UO 2 ) in the presence of dissolved carbonate. A rapid release of U occurred immediately after FeS addition without exhibiting a temporary inhibition stage, as was observed during the oxidation of UO 2 , although FeS still kept DO levels low. X-ray photoelectron spectroscopy (XPS) characterized a transient surface Fe(III) species during the initial FeS oxidation, which was likely responsible for oxidizing noncrystalline U(IV) in addition to oxygen. In the absence of carbonate, however, the release of dissolved U was significantly hindered as a result of U adsorption by FeS oxidation products. This study illustrates the strong interactions between iron sulfide and U(IV) species during redox transformation and implies the lability of biogenic noncrystalline U(IV) species in the subsurface environment when subjected to redox cycling events.

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Section: ■ Results and Discussionmentioning

confidence: 94%

Section: Synthesis Of Mackinawite and Noncrystalline U(iv)mentioning

confidence: 99%

Section: Environmental Science and Technologymentioning

confidence: 99%