Consistent interpretation of the results of through-, out-diffusion and tracer profile analysis for trace anion diffusion in compacted montmorillonite

Glaus, Martin A.; Frick, Sabrina; Rossé, Roger; Loon, Luc R. Van

doi:10.1016/j.jconhyd.2010.11.009

Cited by 29 publications

(21 citation statements)

References 16 publications

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“…These end effects can cause the porosity of clay samples to increase significantly near their extremities (Glaus et al, 2010(Glaus et al, , 2011. This type of artifact most significantly influences the results of ID experiments (Van Loon and Jakob, 2005).…”

Section: Experimental Challengesmentioning

confidence: 99%

“…This type of artifact most significantly influences the results of ID experiments (Van Loon and Jakob, 2005). In situations where end effects and mass transfer through the porous filters play important roles, the precision of calculated diffusion parameters can be significantly increased by measuring the concentration profile of the species of interest in the porous medium at the end of the experiment (Glaus et al, 2011).…”

Section: Experimental Challengesmentioning

confidence: 99%

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Self-Diffusion of Water and Ions in Clay Barriers

Bourg

Tournassat

2015

Developments in Clay Science

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Section: Experimental Challengesmentioning

confidence: 99%

Section: Experimental Challengesmentioning

confidence: 99%

Self-Diffusion of Water and Ions in Clay Barriers

Bourg

Tournassat

2015

Developments in Clay Science

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“…The answer to this question has important implications for the migration of salts and groundwater through clay-rich rocks (Fritz, 1986;Leroy et al, 2006), the design of engineered nanofluidic systems (Schoch et al, 2008;Bocquet and Charlaix, 2010), the performance of desalination membranes (Richards et al, 2012), and the transport of ions through channels in cell membranes (Nikaido and Rosenberg, 1981;Nikaido, 2003). It also is of importance to highlevel radioactive waste (HLRW) management, where the performance of geologic repositories is determined, in many cases, by the migration of anionic, long-lived fission products ( 129 I À , 99 TcO 4 À , 36 Cl À ) through nanoporous clay barriers (Tournassat et al, 2007;Altmann, 2008;Claret et al, 2010;Glaus et al, 2011;Altmann et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulations of Anion Exclusion in Clay Interlayer Nanopores

Tournassat

Bourg

Holmboe

et al. 2016

Clays and clay miner.

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Abstract-The aqueous chemistry of water films confined between clay mineral surfaces remains an important unknown in predictions of radioelement migration from radioactive waste repositories. This issue is particularly important in the case of long-lived anionic radioisotopes ( 129 I À , 99 TcO 4 À , 36 Cl À ) which interact with clay minerals primarily by anion exclusion. For example, models of ion migration in clayey media do not agree as to whether anions are completely or partially excluded from clay interlayer nanopores. In the present study, this key issue was addressed for Cl À using MD simulations for a range of nanopore widths (6 to 15 Å ) overlapping the range of average pore widths that exists in engineered clay barriers. The MD simulation results were compared with the predictions of a thermodynamic model (Donnan Equilibrium model) and two pore-scale models based on the Poisson-Boltzmann equation under the assumption that interlayer water behaves as bulk liquid water. The simulations confirmed that anion exclusion from clay interlayers is greater than predicted by the pore-scale models, particularly at the smallest pore size examined. This greater anion exclusion stems from Cl À being more weakly solvated in nano-confined water than it is in bulk liquid water. Anion exclusion predictions based on the PoissonBoltzmann equation were consistent with the MD simulation results, however, if the predictions included an ion closest approach distance to the clay mineral surface on the order of 2.0 Ô 0.8 Å . These findings suggest that clay interlayers approach a state of complete anion exclusion (hence, ideal semi-permeable membrane properties) at a pore width of 4.2 Ô 1.5 Å .

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“…The diffusion of water and ions in water-saturated compacted clay barriers has, therefore, been extensively characterized, though mostly at ambient temperatures (Molera and Eriksen, 2002;Molera et al, 2003;Nakashima, 2003;Wang et al, 2005;Melkior et al, 2009;Tachi et al, 2010;Glaus et al, 2011;Tanaka et al, 2011;Holmboe et al, 2011).…”

Section: Temperature Dependence Of Water and Solute Diffusion In The Ebsmentioning

confidence: 99%