Caesium incorporation and retention in illite interlayers

Fuller, Adam J.; Shaw, Samuel; Ward, Michael B.; Haigh, Sarah J.; Mosselmans, J. Frederick W.; Peacock, Caroline L.; Stackhouse, Stephen; Dent, Andrew J.; Trivedi, Divyesh; Burke, Ian T.

doi:10.1016/j.clay.2015.02.008

Cited by 165 publications

(105 citation statements)

References 52 publications

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“…The predominant hypothesis is that they occur in ''wedge" regions where illite or vermiculite interlayers transition from a collapsed state to an expanded state [18,102,68,107]. The existence of these regions is supported by electron microscopy observations showing that weathering induces a discernible ''fraying" at the edges of illite and mica crystals [62,34], perhaps associated with the replacement of K by solvated Ca near the extremities of the anhydrous interlayers [34]. Second, the cation exchange kinetics and selectivity of the slow sites remain poorly understood, in part because of a lack of long-term adsorption and desorption studies.…”

Section: Introductionmentioning

confidence: 92%

“…Recent efforts have deployed a combination of wet chemistry experiments [102,4,26], high-resolution imaging [47,63,95,34], synchrotron Xray spectroscopy [29,42], and atomistic-level simulations [68,93,44,107] to gain detailed insight into Cs adsorption mechanisms, selectivity, and kinetics. The emerging view from these studies is that Cs adsorption involves at least three types of surface sites: basal sites located on the external basal surfaces of illite particles, slow sites located in anhydrous illite interlayers, and high affinity sites of unclear nature.…”

Section: Introductionmentioning

confidence: 99%

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Molecular dynamics simulations of cesium adsorption on illite nanoparticles

Lammers

Bourg

Okumura

et al. 2017

Journal of Colloid and Interface Science

124

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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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Section: Introductionmentioning

confidence: 92%

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

124

View full text Add to dashboard Cite

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“…The exchange of cations at edge sites can also cause them to collapse, physically enveloping the metal and preventing it from desorbing back into solution. Increased sorption and resistance to desorption may suggest that beryllium is more physically protected by occupying the collapsed frayed edges of illite upon exchange with other interlayer cations as is observed with other metals like cesium (Fuller et al, 2015). Illites' planar surfaces are otherwise tightly held by potassium ions and less accessible relative to the hydrated interlayers of montmorillonite, thus frayed edge sites may be more readily populated.…”

Section: Naclmentioning

confidence: 99%

“…Illite interlayers are occupied and tightly held together almost entirely by potassium ions. However previous work has shown that the edge sites of illite are void of potassium ions due to chemical weathering and are susceptible to infiltration and subsequent expansion by other hydrated cations such as sodium, calcium and magnesium (Fuller et al, 2015). The increase in the interlayer spacing of illite due to cation exchange and has been well documented (Smith, 1967).…”

Section: Naclmentioning

confidence: 99%

Beryllium desorption from minerals and organic ligands over time

Boschi

Willenbring

2016

Chemical Geology

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Beryllium isotopes sorbed to sediments have provided useful tools in the field of geochronology and geomorphology over the last few decades. The use of beryllium isotopes relies on the premise that beryllium sorbed to sediments is unaltered over large timescales. Changes in the environmental chemistry, either in-situ or en route from soil to fluvial system, to the ocean, can cause beryllium desorption and may preclude some beryllium isotopic applications. Four mechanisms were tested to determine the relative desorption potential of beryllium including a reduction in pH, an increase in ionic strength (NaCl) and complexation by soluble organic (malonic acid) and inorganic species (NaF). To assess the relative effect of each mechanism on beryllium desorption from both organic and mineral fractions, we prepared separate solutions of beryllium bound to minerals and organic compounds and measured beryllium concentrations in solution before and after each chemical perturbation. We conclude a reduction in pH resulted in the greatest amount of desorption among the four treatments, removing 97% and 75% of sorbed beryllium from illite and montmorillonite, respectively, and none from the organic ligands tested. The addition of malonic acid and increasing the ionic strength also resulted in desorption from montmorillonite. Although increasing the ionic strength did remove 32% and 8.4% of beryllium from montmorillonite and sulfonate, respectively, the presence of sodium significantly enhanced sorption to illite. The addition of NaF did not result in any beryllium desorption. Our results demonstrate that various chemical processes can promote the exchange of beryllium between solid and dissolved phases, the extent to which depends on the composition of the system. We also related differences in beryllium desorption behavior to complexation mechanisms driving retention among organic and mineral species. We estimate inner sphere complexation is the predominant sorption mechanism among the organic ligands tested due to the minimal amounts of desorption and the large stability constants previously reported in the literature. Additionally, we found that different complexation processes are involved in beryllium sorption to illite versus montmorillonite. Because beryllium desorbed from montmorillonite due to changes in pH, ionic strength and organic acid complexation, we hypothesize that a portion of beryllium-montmorillonite associations involve outer sphere processes, driven by weaker electrostatic attractions. However, beryllium exhibited a unique relationship with illite in that sorption not only involves inner sphere processes but also physical inclusion within collapsed interlayer spaces.

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“…These silicates stabilize Cs on the surface and silicate sheets because of their negative charges. In particular, in the case of 2:1-type layer silicates, Cs is strongly adsorbed at frayed edge sites (FESs) [7][8][9][10]. In this context, it is necessary to understand the stabilization mechanism to analyze the structure of Cs in the clay surface, silicate sheet, and FESs.…”

Section: Introductionmentioning

confidence: 99%

Nuclear Magnetic Resonance Study of Cs Adsorption onto Clay Minerals

Tokuda

Norikawa

Masai

et al. 2016

Radiological Issues for Fukushima’s Revitalized Future

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The release of radioactive cesium into the environment in the aftermath of disasters such as the Fukushima Daiichi disaster poses a great health risk, particularly since cesium easily spreads in nature. In this context, we perform solidstate nuclear magnetic resonance (NMR) experiments to study Cs C ions adsorbed by clay minerals to analyze their local structure. The NMR spectra show two kinds of peaks corresponding to the clays (illite and kaolinite) after immersion in CsCl aqueous solution; the peak at 30 ppm is assigned to Cs C on the clay surface while that at 100 ppm is assigned to Cs C in the silicate sheet in the clay crystal. This result is consistent with the fact that Cs C with smaller coordination number yields a small field shift in the NMR spectra. Moreover, after immersion in KCl aqueous solution, these peaks disappear in the NMR spectra, thereby indicating that our assignment is reasonable. This is because Cs C on the clay surface and in the silicate sheet is easily subject to ion exchange by K C . We believe that our findings will contribute to a better understanding of the pathway through which Cs transfers from the soil to plants and also to the recovery of the agriculture in Fukushima.

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Caesium incorporation and retention in illite interlayers

Cited by 165 publications

References 52 publications

Molecular dynamics simulations of cesium adsorption on illite nanoparticles

Molecular dynamics simulations of cesium adsorption on illite nanoparticles

Beryllium desorption from minerals and organic ligands over time

Nuclear Magnetic Resonance Study of Cs Adsorption onto Clay Minerals

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