Review of the complexation of tetravalent actinides by ISA and gluconate under alkaline to hyperalkaline conditions

Gaona, Xavier; Montoya, Vanessa; Colàs, E.; Grivé, M.; Duro, Lara

doi:10.1016/j.jconhyd.2008.09.017

Cited by 72 publications

(59 citation statements)

References 28 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%

“…4 shows a very similar trend along the An(IV) series for both An(OH) 4 GLU − and An(OH) 4 (aq) complexes. Log * β 0 1,4,1 determined for Np(IV) is very similar to the value re-calculated in [17] for Pu(IV), in agreement with the similarities in Δ f G 0 m (An 4+ ) and ionic radii of the two actinides.…”

Section: Comparison With Other Actinides: Linear Free-energy Relationsupporting

confidence: 86%

“…Linear free-energy relationship (LFER) are often used to assess the reliability of stability constants along the An(IV) series [17][18][19]. The log * β 0 1,4,1 value determined in this work was compared with other data available in the literature for An(IV)(OH) 4 GLU − complexes.…”

Section: Comparison With Other Actinides: Linear Free-energy Relationmentioning

confidence: 99%

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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%

Section: Comparison With Other Actinides: Linear Free-energy Relationsupporting

confidence: 86%

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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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“…Gluconic acid (HGH 4 , Fig. 1) is a polyhydroxy carboxylic acid commonly used as an additive in concrete formulations [2]. As a consequence, it may be found in radioactive waste repositories, where cement materials are used.…”

Section: Introductionmentioning

confidence: 99%

Solubility of ThO₂·xH₂O(am) in the presence of gluconate

Colàs¹,

Grivé

Rojo

et al. 2011

Radiochimica Acta

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Thorium(IV) / Solubility / Gluconate / ComplexationSummary. Thorium complexation with gluconate has been studied from solubility experiments at gluconate concentrations between 10 −6 and 10 −1 mol/l, with pH c between 9 and 13 and I = 0.5 M (NaClO 4 ).Solubility experiments indicate the formation of a 1 : 1 thorium : gluconate complex. The stability constant for this species, extrapolated to I = 0 by using the SIT (specific interaction theory), has been determined to be log 10 K • = −11.5 ± 0.6 for the reaction:In the presence of ThO 2 ·xH 2 O, sorption of the organic ligand onto solid surface seems to limit thorium dissolution.

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“…The conditional constant would need to increase to log K = 14 before a reasonable correspondence between the experimental and calculated values for the post-addition conditions is obtained. This apparent discrepancy merits further investigation, including consideration of ternary complexes that could modify the speciation (Gaona et al, 2008). Using the same estimated stability constant for the pre-addition conditions, where the concentration of SP is only 10 −4 -10 −3 %, the contribution of the organic component Factors affecting the suitability of superplasticiser-amended cement for the encapsulation of radioactive waste Isaacs, Hinchliff, Felipe-Sotelo and Read is negligible when compared to the concentration of Ni(OH) 3 − .…”

Section: Solubility Considerationsmentioning

confidence: 99%

Factors affecting the suitability of superplasticiser-amended cement for the encapsulation of radioactive waste

Isaacs

Hinchliff²,

Felipe-Sotelo

et al. 2018

Advances in Cement Research

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Organic superplasticisers improve the flow properties of cement, offering operational advantages for the disposal of radioactive wastes. However, there are concerns that they could increase the mobility of encapsulated contaminants significantly. The effect of polycarboxylate ether superplasticisers on the solubility of Ni(II), Am(III), Pu(IV) and U(VI) in two cement-equilibrated waters (ordinary Portland cement/pulverised fuel ash (OPC/PFA) and OPC/ground granulated blast-furnace slag (GGBS)) has been assessed. The study included four commercial superplasticisers, three adjuncts (a de-foaming agent, biocide and viscosity modifier) and a bespoke, synthesised superplasticiser from which residual monomer had been removed by dialysis. The commercial products (0·5% w/w dosage) had a much greater effect on metal solubility than the dialysed equivalent, increasing solubility by 2-3 orders of magnitude. As the adjuncts alone showed no effect, the difference between the commercial and synthesised superplasticisers is attributed to small molecules, primarily residual monomers, in the commercial formulations owing to incomplete polymerisation. The distribution of radionuclides in hardened cement pastes corresponds closely to the distribution of superplasticiser, as shown by 14 C-labelling in combination with digital autoradiography and accounting for the bleed observed for certain slag-rich formulations.

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Review of the complexation of tetravalent actinides by ISA and gluconate under alkaline to hyperalkaline conditions

Cited by 72 publications

References 28 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

Solubility of ThO₂·xH₂O(am) in the presence of gluconate

Factors affecting the suitability of superplasticiser-amended cement for the encapsulation of radioactive waste

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Review of the complexation of tetravalent actinides by ISA and gluconate under alkaline to hyperalkaline conditions

Cited by 72 publications

References 28 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

Solubility of ThO2·xH2O(am) in the presence of gluconate

Factors affecting the suitability of superplasticiser-amended cement for the encapsulation of radioactive waste

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Solubility of ThO₂·xH₂O(am) in the presence of gluconate