Interaction of bentonite colloids with Cs, Eu, Th and U in presence of humic acid: A flow field-flow fractionation study

Bouby, M.; Geckeis, Horst; Lützenkirchen, Johannes; Mihai, S. A.; Schäfer, Thorsten

doi:10.1016/j.gca.2011.04.015

Cited by 47 publications

(30 citation statements)

References 46 publications

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“…The results are summarized in Table 4. According to literature, the clay aggregate dimensions reported in this work are plausible (Schramm and Kwak, 1982a, b;Sposito, 1992;Plaschke et al, 2001;Hauser et al, 2002;Missana et al, 2003;Tournassat et al, 2003;Bergaya et al, 2006;Bouby et al, 2011;Tournassat et al, 2011). The aspect ratio values determined agree with literature data (Plaschke et al, 2001;Tournassat et al, 2003;Cadene et al, 2005;Gélinas and Vidal, 2010;Tournassat et al, 2011;Ali and Bandyopadhyay, 2013;Veghte and Freedman, 2014;Weber et al, 2014).…”

Section: Samplesupporting

confidence: 88%

“…AsFlFFF/UV-vis./MALLS/ICP-MS has previously been used for the characterization of natural or synthetic clay colloids (Plaschke et al, 2001;Bouby et al, 2004;Bouby et al, 2011;Bouby et al, 2012;Finck et al, 2012). In this study, the clay dispersions obtained after fractionation (Si) i = 0-3.5 are diluted to~20 mg/L clay particles in SGW before injection into the system.…”

Section: Size Distribution Measurementsmentioning

confidence: 99%

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Montmorillonite colloids: I. Characterization and stability of dispersions with different size fractions

Norrfors

Bouby

Heck

et al. 2015

Applied Clay Science

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Bentonite is planned to be used as a technical barrier in the final storage of spent nuclear fuel and high level vitrified waste. In contact with ground water of low ionic strength, montmorillonite colloids may be released from the bentonite buffer and thereby enhance the transport of radionuclides (RNs) sorbed. In the present case, clay colloids represent aggregates of several clay mineral layers. It is of major importance to determine RN sorption properties for different sizes of montmorillonite aggregates, since size fractionation may occur during particle transport in natural media. In this study, a protocol for size fractionation of clay aggregates is developed, by sequential and direct centrifugation, in the presence and absence of organic matter. Seven colloidal fractions of different mean aggregate sizes are obtained ranging, when considering the mean equivalent hydrodynamic sphere diameter (ESD), from~960 nm down to~85 nm. Applying mathematical treatments (Jennings and Parslow, 1988) and approximating the clay aggregates to regular disc-shaped stacks of clay mineral sheets result in mean surface diameters varying from~1.5 μm down to~190 nm. All these colloidal fractions are characterized by XRD, IC and ICP-OES where they are found to have the same chemical composition. The number of edge sites (aluminol and silanol) is estimated (in mol/kg) for each colloidal fraction according to (Tournassat et al., 2003). It is calculated from the mean particle sizes obtained from AsFlFFF and PCS measurements, where the clay aggregates are approximated to regular disc-shaped stacks of clay mineral sheets. The estimated number of edge sites varies significantly for the different clay dispersions. In addition, stability studies using the various clay colloidal fractions are performed by the addition of NaCl, CaCl 2 or MgCl 2 , in the presence or absence of organic matter, where no difference in stability is found.

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Section: Samplesupporting

confidence: 88%

Section: Size Distribution Measurementsmentioning

confidence: 99%

Montmorillonite colloids: I. Characterization and stability of dispersions with different size fractions

Norrfors

Bouby

Heck

et al. 2015

Applied Clay Science

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“…The colloid stock suspensions were probed by Asymmetric Flow Field-Flow Fractionation (AsFlFFF) (Postnova Analytics, Landsberg, Germany; HRFFF 10.000 AF4) coupled to UV-Vis spectrophotometry and ICP-MS. The experimental equipment used in this study has been detailed in Bouby et al (2004Bouby et al ( , 2008Bouby et al ( , 2011. In this study, the carrier solution consists of ultra-pure water adjusted to pH 9.3 by addition of ultra-pure NaOH 1 M (Merck).…”

Section: Asymmetric Flow Field-flow Fractionationmentioning

confidence: 99%

“…The determination of FEBEX bentonite colloid mobility/recovery in previous studies (Mö ri et al, 2003;Kurosawa et al, 2006;Missana et al, 2008;Huber et al, 2011) revealed partly high uncertainties and furthermore differences between radionuclide desorption rates determined in laboratory batch and column experiments. The different detection methods used in these studies (mobile laserinduced-breakdown-detection (LIBD), acoustic LIBD and ICP-MS Al-Si concentration) revealed considerably different recovery values Bouby et al, 2011). One particular problem concerns the ICP-MS Al and Si sensitivity.…”

Section: Introductionmentioning

confidence: 97%

Radionuclide desorption kinetics on synthetic Zn/Ni-labeled montmorillonite nanoparticles

Huber

Heck

Truche

et al. 2015

Geochimica et Cosmochimica Acta

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International audienceSorption/desorption kinetics for selected radionuclides (Tc-99(VII), Th-232(IV), U-233(VI), Np-237(V), Pu-242 and Am-243(III)) under Grimsel (Switzerland) ground water conditions (pH 9.7 and ionic strength of similar to 1mM) in the presence of synthetic Zn or Ni containing montmorillonite nanoparticles and granodiorite fracture filling material (FFM) from Grimsel were examined in batch studies. The structurally bound Zn or Ni in the octahedral sheet of the synthetic colloids rendered them suitable as colloid markers. Only a weak interaction of the montmorillonite colloids with the fracture filling material occurs over the experimental duration of 10,000 h (similar to 13 months). The tri- and tetravalent radionuclides are initially strongly associated with nanoparticles in contrast to Tc-99(VII), U-233(VI) and Np-237(V) which showed no sorption to the montmorillonite colloids. Radionuclide desorption of the nanoparticles followed by sorption to the fracture filling material is observed for Th-232(IV), Pu-242 and Am-243(III). Based on the conceptual model that the driving force for the kinetically controlled radionuclide desorption from nanoparticles and subsequent association to the FFM is the excess in surface area offered by the FFM, the observed desorption kinetics are related to the colloid/FFM surface area ratio. The observed decrease in concentration of the redox sensitive elements Tc-99(VII), U-233(VI) and Np-237(V) may be explained by reduction to lower oxidation states in line with Eh-pH conditions prevailing in the experiments and thermodynamic considerations leading to (i) precipitation of a sparingly soluble phase, (ii) sorption to the fracture filling material, (iii) possible formation of eigencolloids and/or (iv) sorption to the montmorillonite colloids. Subsequent to the sorption/ desorption kinetics study, an additional experiment was conducted investigating the potential remobilization of radionuclides/ colloids attached to the FFM used in the sorption/desorption kinetic experiments by contacting this FFM with pure Grimsel groundwater for 7 days. A positive correlation of Pu-242, Th-232(IV) and Np-237 was observed with the Zn and Ni concentrations in the desorption experiments indicating a remobilization of sorbed montmorillonite colloids. The results of the study in hand highlight (i) the novel use of structural labeled colloids to decrease the uncertainties in the determination of nanoparticle attachment providing more confidence in the derived radionuclide desorption rates. Moreover, the data illustrate (ii) the importance of radionuclide colloid desorption to be considered in the analysis and application of colloid facilitated transport both in laboratory or in-situ experiments and numerical model simulations and (iii) a possible remobilization of sorbed colloids and associated radionuclides by desorption from the matrix material (FFM) under non-equilibrium conditions

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“…As demonstrated Pu atoms, as indicated by diffraction studies (Soderholm et al, 2008). On the contrary, clay colloids tend to aggregate and form larger colloidal particles, due to their diminished repulsive energies during the aging period (Bouby et al, 2011;Xie et al, 2012). reduced was not further polymerized because an increase in P >1.5nm was not observed in Fig.…”

Section: Pu(iv) Polymer Stability As Affected By Aging At Room Tempermentioning

confidence: 88%

Trace-level plutonium(IV) polymer stability and its transport in coarse-grained granites

et al. 2015

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Interaction of bentonite colloids with Cs, Eu, Th and U in presence of humic acid: A flow field-flow fractionation study

Cited by 47 publications

References 46 publications

Montmorillonite colloids: I. Characterization and stability of dispersions with different size fractions

Montmorillonite colloids: I. Characterization and stability of dispersions with different size fractions

Radionuclide desorption kinetics on synthetic Zn/Ni-labeled montmorillonite nanoparticles

Trace-level plutonium(IV) polymer stability and its transport in coarse-grained granites

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