Effect of particle size on the diffusion behavior of some radionuclides in compacted bentonite

Kozaki, Tamotsu; Sato, Yuichi; Nakajima, Maiko; Kato, Hirohisa; Sato, Shunsuke; Ôhashi, Hiroshi

doi:10.1016/s0022-3115(98)00782-x

Cited by 78 publications

(42 citation statements)

References 15 publications

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“…If Ca 2+ ions preferentially occupy the sites in interlayer spaces in Na-montmorillonite aggregates, it is likely that, unlike for HTO which can be considered to diffuse in pore water, Ca 2+ ions could diffuse predominantly in interlayer spaces, the basal spacing of which was determined to be constant by the XRD technique. Kozaki et al, 1999b). and the previous studies (Ca 2+ ionic equivalent fraction of 0, Kozaki et al, 2001a).…”

Section: +supporting

confidence: 67%

“…The uncertainties of the apparent diffusion coefficients were evaluated to be less than 3 % by statistics with a confidence limit of 95% in all cases. Reproducibility of the apparent diffusion coefficient for HTO was evaluated in the previous paper in which the same diffusion experiment was repeated several times (Kozaki et al, 1999b). For HTO in Na-montmorillonite at the dry density of 1.0 Mg m -3 , the average value of the apparent diffusion coefficients and the confidence interval calculated from 6 measurements with the confidence limit of 95% were 2.07±0.2510 -10 m 2 s -1 .…”

Section: Resultsmentioning

confidence: 99%

“…(Kozaki et al, 2005) and Cs + (Kozaki et al, 1999a). Kozaki et al, 1999b, n is the number of data) Figure 5…”

Section: +mentioning

confidence: 99%

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Effect of exchangeable cations on apparent diffusion of Ca2+ ions in Na- and Ca-montmorillonite mixtures

Kozaki

Sawaguchi

Fujishima

et al. 2010

Physics and Chemistry of the Earth, Parts A/B/C

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Compacted Na-bentonite, of which the major mineral is montmorillonite, is a candidate buffer material for the geological disposal of high-level radioactive waste. A potential alteration of the bentonite in a repository is the partial replacement of the exchangeable cations of Na However, the apparent diffusion coefficient of Ca 2+ and the activation energy for diffusion at the same dry density were independent of the ionic equivalent fraction of Ca 2+ ions. These findings suggest that unlike HTO, which can be postulated to diffuse mainly in pore water, Ca 2+ ion diffusion could occur predominantly in interlayer spaces, of which the basal spacing was determined to be constant by the XRD technique.

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Section: +supporting

confidence: 67%

Section: Resultsmentioning

confidence: 99%

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Effect of exchangeable cations on apparent diffusion of Ca2+ ions in Na- and Ca-montmorillonite mixtures

Kozaki

Sawaguchi

Fujishima

et al. 2010

Physics and Chemistry of the Earth, Parts A/B/C

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“…Kozaki and coworkers used purified Kunipia-F bentonite (11,(25)(26)(27)(28)(29) or mixtures of purified 112…”

Section: Introductionmentioning

confidence: 99%

Modeling Cation Diffusion in Compacted Water-Saturated Sodium Bentonite at Low Ionic Strength

Bourg

Sposito

Bourg

2007

Environ. Sci. Technol.

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23Sodium bentonites are used as barrier materials for the isolation of landfills and are under 24 consideration for a similar use in the subsurface storage of high-level radioactive waste. The 25 performance of these barriers is determined in large part by molecular diffusion in the bentonite 26 pore space. We tested two current models of cation diffusion in bentonite against experimental 27 data on the relative apparent diffusion coefficients of two representative cations, sodium and 28 strontium. On the 'macropore/nanopore' model, solute molecules are divided into two categories, 29 with unequal pore-scale diffusion coefficients, based on location: in macropores or in interlayer 30 nanopores. On the 'surface diffusion' model, solute molecules are divided into categories based 31 on chemical speciation: dissolved or adsorbed. The macropore/nanopore model agrees with all 32 experimental data at partial montmorillonite dry densities ranging from 0.2 (a dilute bentonite 33 gel) to 1.7 kg dm -3 (a highly compacted bentonite with most of its pore space located in 34 interlayer nanopores), whereas the surface diffusion model fails at partial montmorillonite dry 35 densities greater than about 1.2 kg dm -3 . 36 37

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“…Adsorption methodologies have been proposed as an alternative process for resolving such problems [3][4][5][6][7][8]. Adsorption of radionuclides on clay minerals has been studied intensively in the last decades [9][10][11][12][13][14][15][16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Study on adsorption behavior and separation efficiency of naturally occurring clay for some elements by batch experiments

et al. 2012

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KEYWORDSThis paper describes the versatile nature of clay that was obtained from Suez Gulf, Suez city, Egypt, as a new low cost natural resource which is non toxic to ecosystem and highly effective adsorbent material. The properties of the natural clay and its significance in removing Th(IV) and Ce(IV) as a representative of tetravalent actinides and lanthanides, respectively, La(III) as a representative of trivalent lanthanides as well as homologues of americium and Sr(II) as one of the fission products, in aqueous solutions have been studied, in order to consider its application for nuclear waste treatment. Batch experiments have been carried out to determine the effect of various factors such as initial metal ion concentration, clay dose, pH, contact time, and temperature on the adsorption process. The results have dictated that, the adsorption efficiency of the natural clay was significantly high at pH = 4. Maximum metal ion uptake capacity of clay has been obtained from batch studies was 99.24, 98.21, 77.76 and 57.94% for Th(IV), Ce(IV), La(III) and Sr(II), respectively. The thermodynamic parameters (H o , S o and G o ) have been calculated from the temperature dependent adsorption isotherms. Furthermore, separation factors () have been calculated in order to separate these elements from each other at pH = 4. Adsorption Natural clay Separation factor Radioactive waste Batch experiments Thermodynamic parameters

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Effect of particle size on the diffusion behavior of some radionuclides in compacted bentonite

Cited by 78 publications

References 15 publications

Effect of exchangeable cations on apparent diffusion of Ca2+ ions in Na- and Ca-montmorillonite mixtures

Effect of exchangeable cations on apparent diffusion of Ca2+ ions in Na- and Ca-montmorillonite mixtures

Modeling Cation Diffusion in Compacted Water-Saturated Sodium Bentonite at Low Ionic Strength

Study on adsorption behavior and separation efficiency of naturally occurring clay for some elements by batch experiments

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