Local structural information of Cs in smectite hydrates by means of an EXAFS study and molecular dynamics simulations

Nakano, Masashi; Kawamura, Katsuyuki; Ichikawa, Yasuaki

doi:10.1016/s0169-1317(03)00082-6

Cited by 50 publications

(48 citation statements)

References 21 publications

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“…-MMT, the first-and the second-neighbor back-scattered atoms derived from EXAFS analyses are presumed to be oxygen atoms from the interlayer water and oxygen atoms from MMT surface. There are about 5 water molecules [27] b MCY model estimates based on MD simulation [40] surrounded K ? ion and additional 6 oxygen atoms from each closest silicates tetrahedral sheet.…”

Section: Discussionmentioning

confidence: 99%

“…, Cs 1? , and others in clays has been reported [20][21][22][23][24][25][26][27]. In addition to this experimental investigation, molecular simulation such as Monte Carlo (MC) and molecular dynamics (MD) is also an alternative way to gain an insight at an atomistic level for the structure and dynamics of ions in solution and in hydrated clay minerals [28][29][30][31][32], in particular, an interest in the swelling of MMT clays and hydration of their interlayer cations.…”

Section: Introductionmentioning

confidence: 98%

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A combined X-ray absorption spectroscopy and molecular dynamic simulation to study the local structure potassium ion in hydrated montmorillonite

2015

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Atomistic local structure of potassium ion adsorbed in hydrated montmorillonite (MMT) was investigated based on a combination of an extended X-ray absorption fine structure (EXAFS) spectroscopy and classical molecular dynamics (MD) simulation. The accuracy of the representative MMT atomistic model with PCFF-INTERFACE force field was validated. MD-simulated EXAFS spectra were calculated from trajectories of hydrated MMT atomic coordinates and the results were in satisfactory agreement with corresponding experimental EXAFS spectra. Interlayer spacing determined by X-ray diffraction was consistent with the mono-layer hydrated MMT structure. The first coordination shell of K ? ion in monohydrated MMT was formed by 5 water oxygen atoms at an average K-O W distance of 2.85 Å and the second coordination shell of 6 oxygen atoms from both sides of the closest silicate tetrahedral sheet at K-O MMT = 3.41 Å . For hydrated K ? -MMT, MD and EXAFS results confirm that K ? counter ions form the inner-sphere surface complex and that the adsorbed sites were located with the vicinity edge of a basal oxygen hexagonal cavity in the silicate tetrahedral sheets of MMT. For higher-layer hydrated MMT, K ? ions can form surface complexes that are inner-sphere, outersphere, and transient diffuse-layer species depending on the number of intercalated water in the clay. Water molecules are of less ordered arrangement in the monohydrated MMT due to the confinement effect from the clay surface. K ? counter ions in the single layer hydrates are almost trapped within the cavities of the basal planes surface.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

A combined X-ray absorption spectroscopy and molecular dynamic simulation to study the local structure potassium ion in hydrated montmorillonite

2015

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“…EXAFS analyses have been successfully conducted to explore the local structures of Cs adsorption on clay minerals (Bostick et al, 2002;Nakano et al, 2003) and crown ethers (Kemner et al, 1996;Antonio et al, 1997). Figures 2A and B show the k 3 -weighted χ(k) spectra of Cs L III -edge EXAFS and their radical structural functions (RSF, phase shift not corrected) for CsCl solution, Csadsorbed vermiculite, and Cs adsorbed on the natural samples.…”

Section: Cs L Iii -Edge Exafsmentioning

confidence: 99%

Investigation of cesium adsorption on soil and sediment samples from Fukushima Prefecture by sequential extraction and EXAFS technique

et al. 2012

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“…Atomistic simulation techniques such as molecular dynamics (MD) simulations and density functional theory (DFT) calculations can, in principle, circumvent these difficulties by allowing a direct observation of individual Cs ions on different surface sites. Existing simulation studies have probed cesium adsorption in the interlayer nanopores of swelling clay minerals [64,97,78,79,10,44], in anhydrous clay interlayers [79,93], and at illite and vermiculite wedge sites [68,107]. However, no existing atomistic simulation study has examined cesium adsorption selectivity on different surfaces of a single illite particle, because of two methodological challenges.…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics simulations of cesium adsorption on illite nanoparticles

Lammers

Bourg

Okumura

et al. 2017

Journal of Colloid and Interface Science

116

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The charged surfaces of micaceous minerals, especially illite, regulate the mobility of the major radioisotopes of Cs (Cs, Cs,Cs) in the geosphere. Despite the long history of Cs adsorption studies, the nature of the illite surface sites remains incompletely understood. To address this problem, we present atomistic simulations of Cs competition with Na for three candidate illite adsorption sites - edge, basal plane, and interlayer. Our simulation results are broadly consistent with affinities and selectivities that have been inferred from surface complexation models. Cation exchange on the basal planes is thermodynamically ideal, but exchange on edge surfaces and within interlayers shows complex, thermodynamically non-ideal behavior. The basal planes are weakly Cs-selective, while edges and interlayers have much higher affinity for Cs. The dynamics of NaCs exchange are rapid for both cations on the basal planes, but considerably slower for Cs localized on edge surfaces. In addition to new insights into Cs adsorption and exchange with Na on illite, we report the development of a methodology capable of simulating fully-flexible clay mineral nanoparticles with stable edge surfaces using a well-tested interatomic potential model.

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Local structural information of Cs in smectite hydrates by means of an EXAFS study and molecular dynamics simulations

Cited by 50 publications

References 21 publications

A combined X-ray absorption spectroscopy and molecular dynamic simulation to study the local structure potassium ion in hydrated montmorillonite

A combined X-ray absorption spectroscopy and molecular dynamic simulation to study the local structure potassium ion in hydrated montmorillonite

Investigation of cesium adsorption on soil and sediment samples from Fukushima Prefecture by sequential extraction and EXAFS technique

Molecular dynamics simulations of cesium adsorption on illite nanoparticles

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