Cation diffusion in the electrical double layer enhances the mass transfer rates for Sr2+, Co2+ and Zn2+ in compacted illite

Glaus, Martin A.; Aertsens, Marc; Appelo, C.A.J.; Kupcik, T.; Maes, N.; Laer, L. Van; Loon, Luc R. Van

doi:10.1016/j.gca.2015.06.014

Cited by 42 publications

(27 citation statements)

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“…EDL structures are not only determined by the surface charge density but also by the ion properties such as their radii and hydrated structures as well as hydration energies. As a result of the EDL formation, properties of the liquid such as viscosity, diffusion coefficient, structuring at the interface differ significantly from bulk values. A detailed understanding of the molecular structure of EDLs is essential for many chemical and engineering processes, such as adsorption, adhesion, catalysis, electrochemical processes, clay swelling, colloidal dispersions, or the biomedical sciences …”

Section: Introductionmentioning

confidence: 99%

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Anion Layering and Steric Hydration Repulsion on Positively Charged Surfaces in Aqueous Electrolytes

Weber

Cheng

et al. 2017

ChemPhysChem

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The molecular structure at charged solid/liquid interfaces is vital for many chemical or electrochemical processes, such as adhesion, catalysis, or the stability of colloidal dispersions. How cations influence structural hydration forces and interactions across negatively charged surfaces has been studied in great detail. However, how anions influence structural hydration forces on positively charged surfaces is much less understood. Herein we report force versus distance profiles on freshly cleaved mica using atomic force microscopy with silicon tips. We characterize steric anion hydration forces for a set of common anions (Cl , ClO , NO , SO and PO ) in pure acids at pH ≈1, where protons are the co-ions. Solutions containing anions with low hydration energies exhibit repulsive structural hydration forces, indicating significant ion and/or water structuring within the first 1-2 nm on a positively charged surface. We attribute this to specific adsorption effects within the Stern layer. In contrast, ions with high hydration energies show exponentially repulsive hydration forces, indicating a lower degree of structuring within the Stern layer. The presented data demonstrates that anion hydration forces in the inner double layer are comparable to cation hydration forces, and that they qualitatively correlate with hydration free energies. This work contributes to understanding interaction processes in which positive charge is screened by anions within an electrolyte.

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Section: Introductionmentioning

confidence: 99%

“…Cation structuring at negatively charged surfaces was studied in much greater detail compared to anion structuring . For example, recently Bourg and Fenter combined X‐ray reflectivity (XRR) measurement and MD simulations and reported the Stern layer structure and energetics of alkali chloride solutions on mica surfaces.…”

Section: Introductionmentioning

confidence: 99%

Anion Layering and Steric Hydration Repulsion on Positively Charged Surfaces in Aqueous Electrolytes

Weber

Cheng

et al. 2017

ChemPhysChem

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“…In classical isotopic tracer diffusion experiments (Molera and Eriksen 2002;Van Loon et al 2003Descostes et al 2008;Wersin et al 2008;Tachi and Yotsuji 2014;Glaus et al 2015;Dagnelie et al 2018), the concentration of the diffusing species i is very low compared to the constant electrolyte background concentration. Under these conditions, Equation 35reduces to:…”

Section: Coupled Transport Processes In Reactive Transport Codes-the mentioning

confidence: 99%

“…In practice, the geometrical factor values of diffuse layer and bulk water, as well as the concentration distribution between the bulk porosity and the diffuse layer in the dual continuum model, are fitted on experimental data. Reactive transport calculations have been essential to decipher and quantify the mechanisms explaining the contrasting diffusional behavior of cations, anions and neutral species in clay materials (Appelo and Wersin 2007;Appelo et al 2010;Glaus et al 2013Glaus et al , 2015Tournassat and Steefel 2015;Tinnacher et al 2016;Soler et al 2019). The fact that the accumulation of cations in the diffuse layer enhances their effective diffusion coefficient…”

Section: Coupled Transport Processes In Reactive Transport Codes-the mentioning

confidence: 99%

Reactive Transport Modeling of Coupled Processes in Nanoporous Media

Tournassat

Steefel

2019

Reviews in Mineralogy and Geochemistry

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“…Numerical methods for modeling macroscopic properties of clay media with the consideration of the presence of a diffuse ion swarm have attracted growing interest from diverse communities in the past years [9,[14][15][16][17]. Yet, the number of codes that can handle the coupling between transport properties in clay affected by the presence of a diffuse layer in the porosity and chemical reactions is very limited.…”

Section: Introductionmentioning

confidence: 99%

Modeling diffusion processes in the presence of a diffuse layer at charged mineral surfaces: a benchmark exercise

Tournassat

Steefel

2019

Comput Geosci

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The electrostatic properties of clay mineral surfaces play a significant role in their diffusion properties. The negative electrostatic potential field at clay mineral surfaces results in the presence of a diffuse layer that balances the mineral surface charge. The diffusion properties of the porosity fraction that is affected by this phenomenon are different from the diffusion properties of electroneutral bulk water. These properties have attracted growing interest from diverse communities in the past years, especially in the field of study of radioactive waste disposal. The influence of the diffuse layer can be described at the continuum scale by a set of equations that are formulated in terms of the Nernst-Planck equation. The number of codes that can handle the coupling between transport properties in clay affected by the presence of a diffuse layer in the porosity and chemical reactions is very limited, and no benchmark exercises have been published yet that make it possible to validate the numerical implementation of these equations in reactive transport codes. The present study proposes a set of benchmark exercises of increasing complexity that highlight caveats related to the finite difference (volume) treatment of the Nernst-Planck equation in the presence of a diffuse layer in heterogeneous systems. Once these problems are identified and solved, the codes PHREEQC, CrunchClay, and a new Fortran routine written for this study gave results in very good agreement for most of the benchmark exercises. When present, the differences in results were directly traceable to the differences in averaging methods at grid cell boundaries, and to the consideration or the omission of the activity gradient term in the Nernst-Planck equation.

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Cation diffusion in the electrical double layer enhances the mass transfer rates for Sr2+, Co2+ and Zn2+ in compacted illite

Cited by 42 publications

References 30 publications

Anion Layering and Steric Hydration Repulsion on Positively Charged Surfaces in Aqueous Electrolytes

Anion Layering and Steric Hydration Repulsion on Positively Charged Surfaces in Aqueous Electrolytes

Reactive Transport Modeling of Coupled Processes in Nanoporous Media

Modeling diffusion processes in the presence of a diffuse layer at charged mineral surfaces: a benchmark exercise

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