Confinement effects and mechanistic aspects for montmorillonite nanopores

Li, Xiong; Zhu, Chang; Jia, Zengqiang; Yang, Gang

doi:10.1016/j.jcis.2018.03.082

Cited by 42 publications

(22 citation statements)

References 64 publications

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“…In bulk solutions, cation-water interactions decrease as Ca 2+ > Na + > Cs + > K + but change as Ca 2 + > Cs + > Na + ≈ K + near the illite surface. This implies the formation of a complex and specific solution chemistry at the illite-liquid interface, due to the confinement of illite particles and the presence of intrinsic potassium, which agrees well with so-called "surface disruption" phenomena (Greathouse, Hart, Bowers, Kirkpatrick, & Cygan, 2015;Li et al, 2018;. Therefore, it is believed that the adsorption of cations will be far beyond the driven hydration energy (Teppen & Miller, 2006).…”

Section: Implications For the Interfacial Interactionssupporting

confidence: 71%

“…The potential of mean force (PMF) was calculated via umbrella sampling to estimate the free energy profiles of cations at the surface of illite, as in other studies (Kobayashi et al, 2017;Li et al, 2018;Loganathan & Kalinichev, 2017). The distance normal to the external surface of illite was selected as the reaction coordinate.…”

Section: Discussionmentioning

confidence: 99%

“…The potential of mean force (PMF) for Na + /K 0+ (Figure 7a,b) and Cs + /K 0+ (Figure 7c,d) adsorption onto the surface of illite was calculated in order to analyse the effect of concentration on the stability of adsorbed cations. Cations with higher adsorption free energy correspond to weaker adsorption affinity and thus have lower stability on the surface (Li et al, 2018;Li, Liu, & Zhang, 2019). During the adsorption of Na + onto the surface, three local minima were located at ~0.19, ~0.39 and ~0.61 nm, corresponding to IS, OS and extended OS species, respectively, in which the last two adsorption types were not obvious in the ADPs (Figure 2).…”

Section: Stability Of Adsorbed Cationsmentioning

confidence: 99%

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Adsorption of cations at the illite–water interface and its effect on intrinsic potassium ions

Xing

Tang

et al. 2021

European J Soil Science

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Na + , K + , Cs + and Ca 2+ are common exogenous cations that could be introduced into soils either via long-term tillage with inorganic fertilizers or the leakage of nuclear waste. However, the manner in which they co-adsorb and compete with the intrinsic potassium ions in illite, the response of intrinsic potassium (K 0+ ), as well as the underlying mechanisms of these interactions, remain unclear. These aspects were explored using molecular dynamics simulations based on a series of concentrations. Because of the competition between exogenous cations and K 0+ , the number of adsorbed exogenous cations such as Na + increased by 11.2, whereas the corresponding number of adsorbed potassium decreased by 14.2, with the increase in concentration from 0.1 to 1.0 molÁL À1 , indicating that long-term application of inorganic fertilizers tends to promote the release of intrinsic potassium. This was further validated from the increased adsorption free energy of IS (inner-sphere) K 0+ , which increased from À54.3 kJÁmol À1 (0.1 molÁL À1 ) to À42.9 kJÁmol À1 (1.0 molÁL À1 ). The stability of both exogenous cations and intrinsic potassium decreased with the increase in concentration. This was mainly caused by the reduction of illite-cation interactions, as evidenced by the radial distribution function analysis. Nonetheless, intrinsic potassium always dominated the competition, as its abundance was lower than that of exogenous cations only beyond 0.7 molÁL À1 . Different exogenous cations exerted diverse effects on the intrinsic potassium and may vary with the concentration, as reflected by the distribution, adsorption number, coordination environment and adsorption stability.Generally, the effect of exogenous cations on intrinsic potassium decreased as Ca 2+ > Na + > Cs + , which may have been caused by the different adsorption sites. These results provide new insight into the environmental effect of the excessive use of inorganic fertilizers and the leakage of radioactive waste in soils. Highlights• Increase in exogenous cations tended to promote the release of intrinsic potassium in illite.

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Section: Implications For the Interfacial Interactionssupporting

confidence: 71%

Section: Discussionmentioning

confidence: 99%

Section: Stability Of Adsorbed Cationsmentioning

confidence: 99%

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Adsorption of cations at the illite–water interface and its effect on intrinsic potassium ions

Xing

Tang

et al. 2021

European J Soil Science

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“…Twenty nanosecond MD simulations were run for each system, and the Newton’s equations of motion were resolved using the leapfrog algorithm with a 2.0 fs time step. The three-dimensional diffusion coefficients ( D ) of water molecules were calculated using the Einstein relation 23,25,26 where r (τ) 2 refers to the mean-square displacement of the center of mass for water molecules over a time interval (τ).…”

Section: Computational Sectionmentioning

confidence: 99%

“…The CLAYFF force field was developed especially for mica and other clay minerals, and its combination with flexible simple point charge water model , has been verified sufficiently to describe the interfacial interactions between clay minerals and water. ,,− Gromacs 4.6.5 software was used. The Ewald electrostatic summation and van der Waals interactions were defined with the cutoff radii of 12.0 Å, and the long-range electrostatic interactions were handled by the particle-mesh-Ewald method.…”

Section: Computational Sectionmentioning

confidence: 99%

Structure, Dynamics, and Stability of Water Molecules during Interfacial Interaction with Clay Minerals: Strong Dependence on Surface Charges

et al. 2019

ACS Omega

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Water participates actively in a wide range of interfacial adsorption and reaction processes, and its structure, dynamics, and stability, all of which are crucial to these processes, have been addressed in the present study by means of molecular dynamics simulations. The structure and dynamic behaviors of interfacial water are distinct from those of bulk water and rely strongly on the amounts of surface charges in clay minerals; for example, H-bonds exist predominately among the interfacial water molecules for zero and low surface charges, whereas prevail between the water molecules and clay surfaces for high surface charges. Stabilities of the interfacial water molecules oscillate remarkably during an increase of surface charges that first decline and then are pronouncedly enhanced. Surface charges play a critical role during the interfacial clay/water interaction, and the interfacial water molecules are “liquid-like” at zero and low surface charges but “ice-like” at high surface charges. The present results greatly promote our understanding of clays/water interfaces that exist ubiquitously in environmental conditions.

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Development of a simple, molecular dynamics‐based method to estimate the thickness of electrical double layers

Liu

Yang

2020

Soil Science Soc of Amer J

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Electrical double layers (EDL) exist for all interfaces and determination of EDL thicknesses remains a difficult task. In this study, molecular dynamics (MD) simulations are employed aiming to develop a simple method for effective evaluation of EDL thicknesses. The EDL thicknesses at clay minerals/water interfaces are calculated by MD simulations and empirical Debye lengths, considering different electrolyte solutions (NaCl, KCl, CsCl, PbCl2 and CaCl2), electrolyte concentrations (0∼1.28 mol/L) and charge locations (tetrahedral and octahedral substitutions). Both methods predict the comparable EDL thicknesses at very low concentrations and more EDL compressions at higher concentrations, while MD simulations show the significant improvements in three aspects, as more rational declining trends with increase of concentrations (Critical for estimating EDL thicknesses especially in highly concentrated solutions), inclusion of ion‐specific effects (More EDL compression for divalent than univalent metal ions, and distinct EDL thicknesses for different alkali ions) and reflection of strong dependence on charge locations (EDL thicknesses differ for montmorillonite and beidellite and have a milder declining rate for montmorillonite). Insights are also offered regarding the microstructure of EDLs, and results promote the understanding of EDLs that determine all interfacial properties and processes.

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Confinement effects and mechanistic aspects for montmorillonite nanopores

Cited by 42 publications

References 64 publications

Adsorption of cations at the illite–water interface and its effect on intrinsic potassium ions

Adsorption of cations at the illite–water interface and its effect on intrinsic potassium ions

Structure, Dynamics, and Stability of Water Molecules during Interfacial Interaction with Clay Minerals: Strong Dependence on Surface Charges

Development of a simple, molecular dynamics‐based method to estimate the thickness of electrical double layers

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