The Thermodynamics of Plutonium(IV) Complexation by Fluoride and its Effect on Plutonium (IV) Speciation in Natural Waters

Nash, Kenneth L.; Cleveland, J.M.

doi:10.1524/ract.1984.36.3.129

Cited by 17 publications

(4 citation statements)

References 14 publications

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“…The trend in the filterable: nonfilterable Pu ratios may also be attributed to changes in aquatic chemistry along the transect. On entering the aquifer, the Pu may have remained in a dissolved fraction due to the region's high acidity, which would increase actinide solubility and decrease actinide attraction to solid surfaces [6,14], Additionally, high con- (Table 2) [15]. As the dissolved Pu migrated away from the seepage basins, it encountered groundwaters with higher pH levels, resulting in a greater likelihood that the Pu would co-precipitate as filterable particles or sorb to suspended groundwater colloids.…”

Section: Nuclide Size Fractionationmentioning

confidence: 99%

Actinide Association with Groundwater Colloids in a Coastal Plain Aquifer

et al. 1994

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Trace levels of Pu, Am, Cm, and U in an acidic plume have been traveling through a surface aquifer underlying the Savannah River Site, Aiken, SC, at rates appreciably greater than anticipated. The objective of this study was to determine the extent to which each of these actinides was associated with groundwater colloids, a potential cause for the apparent enhanced transport. Contaminated groundwater was recovered along a 1.02 km transect at approximately the rate of groundwater flow, passed though an ultrafiltration system, and then chemically characterized. The filterable (>500 molecular weight) fraction of nuclides increased with reported nuclide distribution coefficients (K d values): Pu > Th > U > Am = Cm > Ra > tritium. The filterable fractions of the strongersorbing nuclides (Pu and Th) increased, whereas those of the weaker-sorbing nuclides (Am, Cm, and Ra) generally decreased with increasing pH (3.4 to 4.0) and distance from the point source. Uranium was equally divided between the dissolved and filterable fractions throughout the transect. At the farthest sampling point in the contaminant plume (0.55 km), all the Pu and Th and none of the Am and Cm were in the filterable fraction. Plutonium appears to have a much greater potential than Am or Cm for moving through the study site in association with mobile colloids. However, Am and Cm pose a much greater threat than Pu of migrating through this system, because almost all of the Pu and relatively little of the Am and Cm were retained by the matrix.

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Section: Nuclide Size Fractionationmentioning

confidence: 99%

Actinide Association with Groundwater Colloids in a Coastal Plain Aquifer

et al. 1994

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“…The chemical and migration behavior of plutonium is controlled by a variety of chemical and geochemical processes, including redox reactions, solubility and hydrolysis, solution complexation and sorption [1]. Plutonium forms strong complexes with a variety of inorganic and organic ligands [2,3]. In most aquatic systems, species of natural organic matter (NOM) constitute an important pool of ligands *Author for correspondence (E-mail: honeyma@mines.edu).…”

Section: Introductionmentioning

confidence: 99%

Plutonium (IV) complexation with citric and alginic acids at low Pu_Tconcentrations

Kantar¹,

Honeyman²

2005

Radiochimica Acta

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Plutonium / Citric acid / Alginic acid / Complexation / BindingSummary. The conditional stability constants for trace-level concentrations of Pu(IV) complexing with citric and alginic acids were determined at pH 4 and an ionic strength of 0.1 M NaCl using an ion-exchange technique. The results of these experiments were analyzed with: 1) the graphical Schubert's approach, 2) a non-linear simulation of 'Schubert'-type data, and 3) an affinity distribution approach to describe the alginic acid. Analysis of the results of ion-exchange data for Pu(IV)-citric acid systems using Schubert's method indicates the formation of a 1 : 1 Pu-citrate complex with a stability constant (log β 1,1 ) of 16.536 ± 0.015 at I = 0.1 M. Alginic acid exhibits a strong affinity for plutonium and, unlike citric acid, the experimental results were interpreted as a mixture of 1 : 2 and 1 : 3 Pu : alginic acid complexes using non-linear Schubert's analysis of ion-exchange data; average conditional stability constants (log β) of 13.479 ± 0.057 and 14.755 ± 0.305 at I = 0.1 M NaCl, respectively, were determined. The results from the ion-exchange experiments were also modeled based on a non-electrostatic, discrete ligand approach in which alginic acid is conceptualized as being composed of a suite of monoprotic acids, HL i , of arbitrarily-assigned pK a (i) values (e.g., 2, 4, 6 and 8). The experimental ion-exchange data were best described by postulating complexation reactions between Pu(IV) and the model ligands L 2 (pK a = 4) and L 3 (pK a = 6), forming the species Pu(L 2 ) 2 2+ and Pu(L 3 ) 3 + , indicating that the Pu(IV) binding by alginic acid occurs mainly through carboxylic groups under the experimental conditions studied.

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“…A program written for the Texas Instruments TI-59 calculator described in a previous publication [7] was modified to permit an essentially unlimited number of data points to be used in the data-fitting procedure. In the present case 46 to 64 data points were fit at each temperature.…”

Section: Discussionmentioning

confidence: 99%

Thermodynamics of the System: Americium(lll)-Fluoride—Stability Constants, Enthalpies, Entropies, and Solubility Product

Nash¹,

Cleveland

1984

Radiochimica Acta

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Stability constants for the 1 : 1 and 1 : 2 complexes between Am 3+ and F" were determined in 0.1 M NaC10 4 media by the cation exchange technique. Complexation enthalpies and entropies were calculated by the application of the van't Hoff relationship to the stability constants determined at 5, 25, and 45°C. The stability constants at 25°C are K, = 386 (± 10), K 2 = 147 (+ 12). The associated enthalpies and entropies are ΔΗ ι = 22.9 (± 1.6) kJ/m, AS, = 126 (± 5) J/m-°K, and ΔΗ 2 = 1.6(±5)kJ/m, AS 2 = 47 (± 17) J/m-°K. In addition, an approximate value for the solubility product of AmF, has been determined (K sp = 5.

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The Thermodynamics of Plutonium(IV) Complexation by Fluoride and its Effect on Plutonium (IV) Speciation in Natural Waters

Cited by 17 publications

References 14 publications

Actinide Association with Groundwater Colloids in a Coastal Plain Aquifer

Actinide Association with Groundwater Colloids in a Coastal Plain Aquifer

Plutonium (IV) complexation with citric and alginic acids at low Pu_Tconcentrations

Thermodynamics of the System: Americium(lll)-Fluoride—Stability Constants, Enthalpies, Entropies, and Solubility Product

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The Thermodynamics of Plutonium(IV) Complexation by Fluoride and its Effect on Plutonium (IV) Speciation in Natural Waters

Cited by 17 publications

References 14 publications

Actinide Association with Groundwater Colloids in a Coastal Plain Aquifer

Actinide Association with Groundwater Colloids in a Coastal Plain Aquifer

Plutonium (IV) complexation with citric and alginic acids at low PuTconcentrations

Thermodynamics of the System: Americium(lll)-Fluoride—Stability Constants, Enthalpies, Entropies, and Solubility Product

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Plutonium (IV) complexation with citric and alginic acids at low Pu_Tconcentrations