Pore-scale study of thermal effects on ion diffusion in clay with inhomogeneous surface charge

Yang, Yuankai; Wang, Moran

doi:10.1016/j.jcis.2017.12.047

Cited by 15 publications

(23 citation statements)

References 41 publications

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“…This study simplifies Na‐bentonite to montmorillonite because they have the similar characteristics of microstructures. The reproduced microstructure contains the major statistical information of porous media and the predictions of ion diffusivity using these microstructures have validated this strategy (González Sánchez et al, 2008; Wang & Pan, 2008; Yang & Wang, 2018b, 2019). Figures 2a and 2b show the photograph and the SEM image of compacted I/S.…”

Section: Modelingmentioning

confidence: 86%

“…A numerical framework based on the lattice Boltzmann method (LBM) was employed to combine a species evolution equation in order to solve the Nernst‐Planck equations. An electrical potential evolution equation was used to solve the Poisson equation on the same set of discrete lattices (Yang & Wang, 2018b, 2019). The corresponding numerical lattice evolution equation for C i P is as follows:

f_{α, i} ((),, bold-italicr + c_{f_{i}} δ t_{f_{i}} e_{α}, t + δ t_{f_{i}}) - f_{α, i} ((), bold-italicr, t) = - \frac{1}{τ_{f_{i}}} ([], f_{α, i} ((), bold-italicr, t) - f_{α, i}^{eq} ((), bold-italicr, t)),

where r is the position vector, δt is the corresponding time step, δx is the lattice size, and e α are the discrete velocities.…”

Section: Modelingmentioning

confidence: 99%

“…Therefore, it is necessary to improve the understanding the influence of the overlapping EDL on anionic concentration and electrical potential distributions. Recently, a 3‐D pore‐scale model has been used to predict the diffusion of ions in clays (Yang et al, 2019; Yang & Wang, 2018b, 2019). Compared with other models, the pore‐scale model can capture the local ionic concentration and electrical potential distributions automatically at the pore scale.…”

Section: Introductionmentioning

confidence: 99%

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Anion Diffusion in Compacted Clays by Pore‐Scale Simulation and Experiments

Yang

Wang

et al. 2020

Water Resources Research

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Accurate understanding of diffusion of anionic radionuclides in different clays is significant to predict long-term performance of high-level radioactive waste (HLW) repositories. The importance of electrical double layer (EDL) on anionic tracer diffusion in different clays has been studied by both through-diffusion experiments and pore-scale simulations in this work. The through-diffusion experiments measured the effective diffusion coefficient and the accessible porosity of Re (VII) in compacted montmorillonite, Na-bentonite, and illite/smectite mixed layer (I/S) at different salinities. The results showed that the accessible porosity and the effective diffusion coefficient of Re (VII) in montmorillonite and Na-bentonite were similar but lower than those in I/S under the same conditions. For mechanism analysis and predictions, a pore-scale modeling was implemented to simulate the diffusion of anions in compacted clays. In the simulations, the characteristics (porosity, density, and total surface area) of microstructures of montmorillonite and I/S were used to regenerate three-dimensional pore structures numerically by a Quartet Structure Generation Set method. The Re (VII) diffusion was then simulated by directly solving coupled Poisson-Nernst-Planck equations via the lattice Boltzmann method. The diminished effect of EDL was therefore calculated and compared with Donnan and multiporosity models. As EDLs overlap in compacted clays, the Donnan model overestimates the influence of EDL on Re (VII) diffusion, while the multiporosity model underestimates it. The pore-scale modeling, which captures the structure of overlapping EDLs automatically, can simulate the diffusion of anionic radionuclides in compacted clays without any fitting parameters.

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Section: Modelingmentioning

confidence: 86%

f_{α, i} ((),, bold-italicr + c_{f_{i}} δ t_{f_{i}} e_{α}, t + δ t_{f_{i}}) - f_{α, i} ((), bold-italicr, t) = - \frac{1}{τ_{f_{i}}} ([], f_{α, i} ((), bold-italicr, t) - f_{α, i}^{eq} ((), bold-italicr, t)),

where r is the position vector, δt is the corresponding time step, δx is the lattice size, and e α are the discrete velocities.…”

Section: Modelingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Anion Diffusion in Compacted Clays by Pore‐Scale Simulation and Experiments

Yang

Wang

et al. 2020

Water Resources Research

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“…shale) and clay soils is essential for underpinning the design and safety assessments of many geotechnical infrastructures such as nuclear waste repositories and groundsource heat or energy foundations. 6,7 Compared to the theoretical studies of thermophoresis, in particular thermal diffusion, [9][10][11][12][13] the microscopic mechanistic understanding of thermo-osmosis is rather incomplete, although its macroscopic thermodynamical description has been widely discussed and used both in modelling multiscalemultiphase couplings problems 14,15 and in experimental works. 16,17 In fact, there is a debate between two approaches for describing the underlying mechanism for thermo-osmosis, namely the interfacial approach and the energetic approach.…”

Section: Introductionmentioning

confidence: 99%

Thermo-osmosis in hydrophilic nanochannels: mechanism and size effect

2021

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“…It was argued that there must be surface charge inhomogeneity at both microscopic (pore‐scale) and macroscopic (field‐scale) scale to explain the deposition rate (Kretzschmar et al, ; Ryan & Elimelech, ; L. F. Song et al, ). On the other hand, better understanding of the ionic transport through complex geometries with inhomogeneously charged surfaces could improve our knowledge of the geological measurements (i.e., streaming potential [Andre Revil & Leroy, ; Revil, Pezard, & Glover, ; Revil, Schwaeger, et al, ]), solute transport for concrete pores (Appelo, ; Yang & Wang, ), diffusion (Yang & Wang, ) and dispersion in porous media (Muniruzzaman et al, ; Rolle et al, ), reactive transport (Alt‐Epping et al, ; Muniruzzaman & Rolle, ; Steefel & Maher, ; Zhang & Wan, ), salt removal and electro‐diffusion of shale layer [Andre Revil & Leroy, ], and underground water quality (Muniruzzaman & Rolle, ).…”

Section: Introductionmentioning

confidence: 99%

Pore‐scale Study of Ion Transport Mechanisms in Inhomogeneously Charged Nanoporous Rocks: Impacts of Interface Properties on Macroscopic Transport

Alizadeh

Wang

2019

JGR Solid Earth

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The electrokinetic transport mechanisms of multispecies ions through 3‐D nanoporous rocks with chemical reaction at the solid‐aqueous solution interfaces are investigated. We systematically study the multiphysics transport phenomena by considering either inhomogeneous (local surface charge based on local pH and ion concentrations) or prescribed homogeneous surface charge at solid‐aqueous solution interface while the pores are screened via electric double layers. We develop a lattice Boltzmann numerical framework to solve the set of governing equations (Poisson‐Nernst‐Planck plus Navier–Stokes). Our modeling results reveal that the averaged local electric potential of the nanoporous rock is significantly underestimated (about 83%) when a homogeneous surface charge is prescribed based on the bulk solution properties. It is shown that increasing the porosity of the nanoporous media considerably increases the absolute values and inhomogeneity of the surface charge, which means that while the electric double layers screened the pores, increasing the porosity enhances the ion selectivity of the porous medium. When the scenario with inhomogeneous charge is taken into account, the predicted electroosmotic permeability and tortuosity are higher in comparison with the prescribed homogeneous case. Moreover, we have studied the electrostatic tortuosity, coupling coefficient, and the effective excess charge density of the nanoporous rocks. The results demonstrate that ignoring the inhomogeneity of surface charges may cause erroneous prediction of the ion transport through porous rocks with chemically active surfaces.

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Pore-scale study of thermal effects on ion diffusion in clay with inhomogeneous surface charge

Cited by 15 publications

References 41 publications

Anion Diffusion in Compacted Clays by Pore‐Scale Simulation and Experiments

Anion Diffusion in Compacted Clays by Pore‐Scale Simulation and Experiments

Thermo-osmosis in hydrophilic nanochannels: mechanism and size effect

Pore‐scale Study of Ion Transport Mechanisms in Inhomogeneously Charged Nanoporous Rocks: Impacts of Interface Properties on Macroscopic Transport

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