Mobilities of uranium species in sedimentary interbed from the Snake River Plain

Fjeld, Robert A.; Coates, John T.; Elzerman, Alan W.; Navratil, J.D.

doi:10.1007/978-3-642-55668-5_33

Cited by 3 publications

(2 citation statements)

References 15 publications

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“…Kersting et al () used X-ray absorption spectroscopy (XAS) to show reduction of Pu(V) by a number of minerals including goethite, birnessite (δ-MnO 2 ), pyrolusite (β-MnO 2 ), and silica. Additionally, reduction of Pu(V) during transport through Idaho National Engineering and Environmental Laboratory interbed sediments and basalt and Savannah River Site (SRS) sediments has been inferred from laboratory column and field lysimeter studies ( − ).…”

Section: Introductionmentioning

confidence: 99%

Pu(V)O₂⁺ Adsorption and Reduction by Synthetic Hematite and Goethite

Powell

Fjeld

Kaplan

et al. 2005

Environ. Sci. Technol.

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132

171

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Changes in aqueous- and solid-phase plutonium oxidation state were monitored over time in hematite (alpha-Fe2O3) and goethite (alpha-FeOOH) suspensions containing 239Pu(V)-amended 0.01 M NaCl. Solid-phase oxidation state distribution was quantified by leaching plutonium into the aqueous phase and applying an ultrafiltration/solvent extraction technique. The technique was verified using oxidation state analogues of plutonium and sediment-free controls of known Pu oxidation state. Batch kinetic experiments were conducted at hematite and goethite concentrations between 10 and 500 m2 L(-1) in the pH range of 3-8. Surface-mediated reduction of Pu(V) was observed for both minerals at pH values of 4.5 and greater. At pH 3 no adsorption of Pu(V) was observed on either goethite or hematite; consequently, no reduction was observed. For hematite, adsorption of Pu(V) was the rate-limiting step in the adsorption/reduction process. In the pH range of 5-8, the overall removal of Pu(V) from the system (solid and aqueous phases) was found to be approximately second order with respect to hematite concentration and of order -0.39 with respect to the hydrogen ion concentration. The overall reaction rate constant (k(rxn)), including both adsorption and reduction of Pu(V), was 1.75+/-2.05 x 10(-10) (m(-2) L)(-2.08) (mol(-1) L)(-0.39) (s(-1)). In contrast to hematite, Pu(V) adsorption to goethite occurred rapidly relative to reduction. At a given pH,the reduction rate was approximately independent of the goethite concentration, although the hydrogen ion concentration (pH) had only a slight effect on the overall reaction rate. For goethite, the overall reaction rates at pH 5 and pH 8 were 6.0 x 10(-5) and 1.5 x 10(-4) s(-1), respectively. For hematite, the reaction rate increased by 3 orders of magnitude across the same pH range.

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Section: Introductionmentioning

confidence: 99%

Pu(V)O₂⁺ Adsorption and Reduction by Synthetic Hematite and Goethite

Powell

Fjeld

Kaplan

et al. 2005

Environ. Sci. Technol.

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132

171

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“…The Pu(VI) was slowly reduced over time until Pu(IV) was the predominant solid-phase species (16). Based upon Pu behavior in laboratory column transport studies using Idaho National Engineering and Environmental Laboratory interbed basalt (21) and Savannah River Site (SRS) sediments (22,23), it was inferred that Pu(V) was reduced to Pu(IV) during transport. Conversely, production of Pu(V) or Pu(VI) has been shown to occur through a water catalyzed reaction on PuO2(s) (24) and also through oxidation of Pu(IV) on manganese oxide (19).…”

Section: Introductionmentioning

confidence: 99%

Pu(V)O₂⁺ Adsorption and Reduction by Synthetic Magnetite (Fe₃O₄)

Powell

Fjeld

Kaplan

et al. 2004

Environ. Sci. Technol.

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137

140

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Changes in aqueous- and solid-phase Pu oxidation state were monitored over time in magnetite (Fe3O4) suspensions containing 239Pu(V)-amended 0.01 M NaCl. Oxidation state distribution was determined by leaching of Pu into an aqueous phase followed by an ultrafiltration/solvent extraction technique. The capability of the technique to measure Pu oxidation state distribution was verified using 230Th(IV), 237Np(V), and 233U(VI) as oxidation state analogues. Reduction of Pu(V) was observed at all pH values (pH 3 to 8) and magnetite concentrations (10 to 100 m2 L(-1)). In the pH range 5 to 8, adsorption was a rate-limiting step, and reduction was mediated by the solid phase; at pH 3 reduction occurred in the aqueous phase. The overall reaction (describing both adsorption and reduction of Pu(V)) was found to be approximately first order with respect to the magnetite concentration and of order -0.34+/-0.02 with respect to the hydrogen ion concentration. Assuming first order dependence with respect to Pu, the overall reaction rate constant was calculated as k(rxn) = 4.79+/-0.62 x 10(-8) (m(-2) L)0.99(mol(-1) L)-0.34(s(-1)). The Pu(IV) solid-phase species became more stable over time.

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