Modelling the Behaviour of Organic Degradation Products

Cross, J E; Ewart, F.T.; Greenfield, B. F.

doi:10.1557/proc-127-715

Cited by 11 publications

(9 citation statements)

References 2 publications

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“…(7) was used to fit the experimental data, allowing the determination of the number of GLU ligands, n, involved in the complexation reaction: n = 1.08 ± 0.15 at pH 13.3 and n = 0.92 ± 0.15 at pH 11. These results indicate the formation of a 1 : 1 Np(IV) : GLU complex in the absence of Ca, in good agreement with previous studies carried out for the systems Th(IV)-, U(IV)-, and Pu(IV)-GLU [5,7,[14][15][16][17]. In the subsequent step, the experimental data were re-fitted, fix- ing the value of "n" to 1 in order to determine the conditional formation constant of the Np -GLU complex in each experiment.…”

Section: Effect Of Glu Onsupporting

confidence: 92%

Thermodynamics of Np(IV) complexes with gluconic acid under alkaline conditions: sorption studies

Rojo¹,

Tits²,

Gaona³

et al. 2013

Radiochimica Acta

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The complexation of Np(IV) with gluconic acid (GLU) under alkaline conditions was investigated in the absence of Ca by carrying out a series of sorption experiments. The decrease of Np(IV) sorption on the sorbing material at increasing concentrations of GLU was interpreted as the formation of Np(IV)-GLU aqueous complexes. The modelling of experimental data according to the Schubert method [1] confirmed the formation of a complex with a Np : GLU ratio 1 : 1. The stoichiometry of the complex Np(OH)4GLU− was proposed based on the experimental observation that no proton exchange occurred during the course of the complexation reaction and that Np(OH)4(aq) was the predominant hydrolysis product in the absence of GLU. A log * β 1,4,1 0 = −2.92 ± 0.30 for the formation reaction Np4+ + 4H2O + GLU−⇔Np(OH)4GLU− + 4H+ was calculated based on the conditional stability constants determined from sorption experiments and using the Np(IV) thermodynamic data selected in the NEA reviews [2]. Linear free energy relationships (LFER) confirmed that the stoichiometry and stability of the Np(IV)-GLU complex characterized in this work are consistent with data available for Th(IV)-, U(IV)- and Pu(IV)-GLU complexes.

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Section: Effect Of Glu Onsupporting

confidence: 92%

Thermodynamics of Np(IV) complexes with gluconic acid under alkaline conditions: sorption studies

Rojo¹,

Tits²,

Gaona³

et al. 2013

Radiochimica Acta

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“…Unfortunately, formation constants for uranium(VI) gluconate complexes have not been reported so values were estimated from the data available for uranium(VI) complexes with other monohydroxycarboxylic acids. The same approach had previously been successfully used to estimate constants for plutonium complexes with organic ligands [18]. Full details of the derivations are given in the HATCHES database [12].…”

Section: (A) Description Of the Modelmentioning

confidence: 99%

Thermodynamic Modelling of the Effect of Organic Complexants on Sorption Behaviour

Bond¹,

Cross²,

Ewart³

1991

Radiochimica Acta

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The results of an experimental study of the sorption of uranium onto clay at pH 8 and pH 11 have been successfully simulated using a triple layer sorption model. The model has been incorporated in a Harwell derivation (HARPHRQ) of the PHREEQE geochemical code. The model has been parameterized using data for sorption onto ferric oxyhydroxide.The experimental study also investigated the effects of hydroxycarboxylic acids on the sorption process. The model has satisfactorily simulated the competing sorption and complexation reactions at pH 8, but sorption at pH 11 is underestimated for low uranium inventories.

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“…d -Gluconate (Gluc – ; Scheme ), being used as an additive in cement, is likely to be present in underground repositories; thus, it is regarded as a general model compound for organic contaminants. Gluc – is known to chelate thorium(IV), , uranium(IV), uranium(VI), , neptunium(IV), plutonium(IV), , and americium(III) in an alkaline medium.…”

Section: Introductionmentioning

confidence: 99%

Magnesium(II) d-Gluconate Complexes Relevant to Radioactive Waste Disposals: Metal-Ion-Induced Ligand Deprotonation or Ligand-Promoted Metal-Ion Hydrolysis?

et al. 2019

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The complexation equilibria between Mg2+ and d-gluconate (Gluc–) ions are of particular importance in modeling the chemical speciation in low- and intermediate-level radioactive waste repositories. NMR measurements and potentiometric titrations conducted at 25 °C and 4 M ionic strength revealed the formation of the MgGluc+, MgGlucOH0, MgGluc(OH)2–, and Mg3Gluc2(OH)40 complexes. The trinuclear species provides indirect evidence for the existence of multinuclear magnesium(II) hydroxido complexes, whose formation was proposed earlier but has not been confirmed yet. Additionally, speciation calculations demonstrated that MgCl2 can markedly decrease the solubility of thorium(IV) at low ligand concentrations. Regarding the structure of MgGluc+, both IR spectra and density functional theory (DFT) calculations indicate the monodentate coordination of Gluc–. By the potentiometric data, the acidity of the water molecules is higher in the MgGluc+ and MgGlucOH0 species than in the Mg(H2O)62+ aqua ion. On the basis of DFT calculations, this ligand-promoted hydrolysis is caused by strong hydrogen bonds forming between Gluc– and Mg(H2O)62+. Conversely, metal-ion-induced ligand deprotonation takes place in the case of calcium(II) complexes, giving rise to salient variations on the NMR spectra in a strongly alkaline medium.

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Modelling the Behaviour of Organic Degradation Products

Cited by 11 publications

References 2 publications

Thermodynamics of Np(IV) complexes with gluconic acid under alkaline conditions: sorption studies

Thermodynamics of Np(IV) complexes with gluconic acid under alkaline conditions: sorption studies

Thermodynamic Modelling of the Effect of Organic Complexants on Sorption Behaviour

Magnesium(II) d-Gluconate Complexes Relevant to Radioactive Waste Disposals: Metal-Ion-Induced Ligand Deprotonation or Ligand-Promoted Metal-Ion Hydrolysis?

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