Investigations into the chemical forms of 239Pu in a West Cumbrian saltmarsh soil radiolabelled by an environmental process

Bulman, Robert A.; Wedgwood, Angela J.; Szabó, Gyula

doi:10.1016/0048-9697(92)90427-t

Cited by 9 publications

(6 citation statements)

References 2 publications

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“…From the chemical features of humic acids, it was evident that they would influence the speciation of plutonium in the environment. Many investigations have confirmed the suppositions [1][2][3][4][5]. The recovery of chelatable plutonium from humates from a salt marsh soil, which had been radiolabelled by a marine environmental process, was sufficient evidence [4] for a series of in vitro investigations of the interaction of transuranic radionuclides with humic acid.…”

Section: Introductionmentioning

confidence: 78%

“…humic substances needs to be understood in sufficient detail to predict interactions of the transuranic element with humate-coated phases that might mediate its movement out of waste repositories [4,[6][7][8]. Satisfactory data on tetravalent and redox sensitive actinides, such as plutonium, are scarce and arise from experimental difficulties posed by the low solubility of their oxide-hydroxide [9,10] and, also, their high affinity for vessel walls [11].…”

Section: Introductionmentioning

confidence: 98%

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Effect of ionic strength on complexation of Pu(IV) with humic acid

Szabó¹,

Guczi

Reiller

et al. 2010

Radiochimica Acta

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International audienceSuccessful geochemical modelling of the migration of radioactive materials, such as the transuranic elements, from nuclear waste repositories is dependent upon an understanding of their interaction with biogeopolymers such as humic acids, the most likely complexing agents in groundwaters. An established silica/humic acid composite has been evaluated as a model substrate for naturally occurring humate-coated minerals that are likely to be present in the vicinity of the repositories. The binding of Pu(IV), the highly likely oxidation station, by the silica/humic substrate was examined at pH 4 in the range 0.02 to 3.00 M NaClO4 by the titration method. Pu(IV)-humate conditional stability constants have been evaluated from data obtained from these experiments by using non-linear regression of binding isotherms. The results have been interpreted in terms of complexes of 1:1 stoichiometry. Analysis of the complex formation dependency with ionic strength shows that the effect of ionic strength on humate complexation of Pu(IV) is not dramatically pronounced. The complexation constants are evaluated for the humate interaction with Pu4+ and Pu(OH)3+ at pH 4. The complexation constants are found, respectively, to be logHAβ0(Pu4+)=16.6±0.3 and logβ01.3.1=46.6±2.3. The estimations through analogy from previous results are in agreement with these new experimental data

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Section: Introductionmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 98%

Effect of ionic strength on complexation of Pu(IV) with humic acid

Szabó¹,

Guczi

Reiller

et al. 2010

Radiochimica Acta

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“…In actinide complexation, the DEF is capable of occupying all available coordination sites,7, 13 which has the effect of blocking adsorption to anionic sites common to mineral oxides typical of the geologic subsurface 14–16. This phenomenon may enhance actinide mobility which could augment the geographic extent of contamination 17–21. Hence finding approaches for sensitive, explicit detection of U complexes (such as those formed with DEF) in groundwater is a focus for our group and others 22–24…”

Section: Introductionmentioning

confidence: 99%

Collision‐induced dissociation tandem mass spectrometry of desferrioxamine siderophore complexes from electrospray ionization of UO₂²⁺, Fe³⁺ and Ca²⁺ solutions

et al. 2004

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Desferrioxamine (DEF) is a trihydroxamate siderophore typical of those produced by bacteria and fungi for the purpose of scavenging Fe(3+) from environments where the element is in short supply. Since this class of molecules has excellent chelating properties, reaction with metal contaminants such as actinide species can also occur. The complexes that are formed can be mobile in the environment. Because the natural environment is extremely diverse, strategies are needed for the identification of metal complexes in aqueous matrices having a high degree of chemical heterogeneity, and electrospray ionization mass spectrometry (ESI-MS) has been highly effective for the characterization of siderophore-metal complexes. In this study, ESI-MS of solutions containing DEF and either UO(2)(2+), Fe(3+) or Ca(2+) resulted in generation of abundant singly charged ions corresponding to [UO(2)(DEF - H)](+), [Fe(DEF - 2H)](+) and [Ca(DEF - H)](+). In addition, less abundant doubly charged ions were produced. Mass spectrometry/mass spectrometry (MS/MS) studies of collision-induced dissociation (CID) reactions of protonated DEF and metal-DEF complexes were contrasted and rationalized in terms of ligand structure. In all cases, the most abundant fragmentation reactions involved cleavage of the hydroxamate moieties, consistent with the idea that they are most actively involved with metal complexation. Singly charged complexes tended to be dominated by cleavage of a single hydroxamate, while competitive fragmentation between two hydroxamate moieties increased when the doubly charged complexes were considered. Rupture of amide bonds was also observed, but these were in general less significant than the hydroxamate fragmentations. Several lower abundance fragmentations were unique to the metal examined: abundant loss of H(2)O occurred only for the singly charged UO(2)(2+) complex. Further, NH(3) was eliminated only from the singly charged Fe(3+) complex; this and fragmentation of C-C and C-N bonds derived from neither the hydroxamate nor the amide groups suggested that Fe(3+) insertion reactions were competing with ligand complexation. In no experiments were coordinating solvent molecules observed, attached either to the intact complexes or to the fragment ions, which indicated that both intact DEF and its fragments were occupying all of the coordination sites around the metal centers. This conclusion was based on previous experiments that showed that undercoordinated UO(2)(2+) and Fe(3+) readily added H(2)O and methanol in the ESI quadrupole ion trap mass spectrometer that was used in this study.

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“…From these studies pH and ionic strength are important terms in describing the sorption of metal ions to humic coated surfaces, similar to results from aqueous complexation studies. The sorption has been empirically modeled [32,43,44], including experiments with humic coated materials [45,46]. However, with a mechanistic approach experimental results can be universally applied.…”

Section: Introductionmentioning

confidence: 99%

Interaction of europium with humic acid covalently bound to silica beads

Czerwinski¹,

Cerefice²,

Buckau³

et al. 2000

Radiochimica Acta

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Humic acid / Complexation / Europium / Stability constantsSummary. The uptake of Eu 3ϩ (a trivalent actinide homolog) by Aldrich humic acid covalently bonded to an inorganic support is examined. Two types of covalent linkages are used and the synthetic routes to produce the resins are discussed. The use of these resins excludes having to account for humic acid desorption from the surface, yields a well characterized system, and allows the experiment to focus on and account for the role of humic acid in the sorption of Eu. The proton exchange capacity of the resins is examined by titration and the differences observed are traced to the resin synthesis. Europium sorption experiments are performed at pH 4 and pH 6 in 0.1 M NaClO 4 . Kinetic experiments show equilibrium is reached in 24 hours. The kinetic data are used to evaluate the loading capacity, with results similar to equilibrium experiments. The complexation results are evaluated based on the metal ion charge neutralization model. For the resins an effect of pH and resin synthesis route on the Eu uptake is observed. The uptake increases with pH for both resins. The resin HAEpo (Epoxy linkage) has a higher metal binding at pH 4, while the resin HA-HAB (2-hydroxylazobenzene linkage) had more proton exchange sites occupied by metal ions at pH 6. Overall, more Eu is bound to HA-Epo at pH 6 since its proton exchange capacity is higher. The evaluated stability constants vary slightly and show a dependence on the linkage group but are similar to literature values that examined complexation by aquatic humic acid analyzed with the same model. This result supports the utility of the metal ion charge neutralization model and the applicability of the resulting stability constants.

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Investigations into the chemical forms of 239Pu in a West Cumbrian saltmarsh soil radiolabelled by an environmental process

Cited by 9 publications

References 2 publications

Effect of ionic strength on complexation of Pu(IV) with humic acid

Effect of ionic strength on complexation of Pu(IV) with humic acid

Collision‐induced dissociation tandem mass spectrometry of desferrioxamine siderophore complexes from electrospray ionization of UO₂²⁺, Fe³⁺ and Ca²⁺ solutions

Interaction of europium with humic acid covalently bound to silica beads

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Investigations into the chemical forms of 239Pu in a West Cumbrian saltmarsh soil radiolabelled by an environmental process

Cited by 9 publications

References 2 publications

Effect of ionic strength on complexation of Pu(IV) with humic acid

Effect of ionic strength on complexation of Pu(IV) with humic acid

Collision‐induced dissociation tandem mass spectrometry of desferrioxamine siderophore complexes from electrospray ionization of UO22+, Fe3+ and Ca2+ solutions

Interaction of europium with humic acid covalently bound to silica beads

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Collision‐induced dissociation tandem mass spectrometry of desferrioxamine siderophore complexes from electrospray ionization of UO₂²⁺, Fe³⁺ and Ca²⁺ solutions