Diffusion of Neptunium(V) in Loosely Compacted Sodium Bentonite

Tsukamoto, Masaki; Ohe, Toshiaki; Fujita, Tomonari

doi:10.1524/ract.1994.6667.s1.397

Cited by 7 publications

(11 citation statements)

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“…On the other hand, ions sorbed directly on the edges of clay minerals have large bonding energies so that they hardly move on the solid surface. The latter phenomenon is supported by the same analysis as the above for Np and Pu diffusion data, indicating pore-diffusion control for those elements [8,10]. For an in-depth discussion of the diffusion mechanism of Cs, we need not only the above analysis but also other experimental and modelling analyses.…”

Section: Resultssupporting

confidence: 60%

“…Figure 3 shows the diffusion profiles with the calculated results shown by the solid lines. Apparent diffusion coefficients (Da) of Cs were estimated by fitting the calculated diffusion curve to the experimental data using the computer code GESPER [8] by the direct search of the optimisation method. The Cs concentration change was considered to be the boundary condition for the calculations (see Table 1).…”

Section: Resultsmentioning

confidence: 99%

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Diffusion measurement of caesium in compacted bentonite

Tsukamoto

Ohe

2003

Czech J Phys

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Caesium diffusion in compacted bentonite beds was studied to determine the transport mechanism. Apparent diffusion coefficients determined at various temperatures indicated a surface diffusion mechanism when compared with values estimated under pore diffusion control assumption. However, temperature dependence of the diffusion coefficients showed a tendency similar to that of pore diffusion. Chemical-transport calculations showed that the cation-exchange reactions possibly described the above disagreement in the mechanism.

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Section: Resultssupporting

confidence: 60%

Section: Resultsmentioning

confidence: 99%

Diffusion measurement of caesium in compacted bentonite

Tsukamoto

Ohe

2003

Czech J Phys

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“…Deprotonation of surface hydroxyl groups exposed at the edge sites of smectite causes overall negative charge in alkaline pH region [7], contributing to surface complexation of Sr 2+ with negatively charged sites. Therefore, both the cation-exchange reactions in the pH range studied and the surface complexation reaction in alkaline pH region were assumed to describe the pH dependence sorption data using a geochemical calculation code GESPER [11] considering formation of typical Sr aqueous species and using thermodynamic data from the literature [13].…”

Section: Resultsmentioning

confidence: 99%

Sorption and diffusion behaviours of strontium in sodium-type bentonite bed

2006

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Sorption and diffusion of Sr were examined using a typical Japanese bentonite. The experimental results showed that Sr sorption on the bentonite had linear relationship between the equilibrium Sr concentration and Sr sorption amount, i.e., Henry's type of sorption, in wide initial Sr concentration from 1.1 × 10 -9 to 1.1 × 10 -4 mol L -1 at pH 10. The Sr sorption also indicated pH dependence in pH range between 2 and 12. Sorption modelling calculation indicated that cationexchange reactions contributed to Sr sorption in the pH range studied and a surface complexation reaction was predominant above pH 8. Diffusion of Sr in loosely compacted bentonite bed was described by pore and surface diffusion and surface complexation of Sr. Chemical-transport calculations reproduce the diffusion data at pH 5 using the cation-exchange parameters obtained in the analysis of the batch sorption experiment.

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“…Carbonate species have been found to enhance the sorption of Np(V) on bentonite [6] and Eu on goethite and magnetite [7], possibly by formation of surface complexation of carbonate complexes at the solid surface [6] or increased sorption sites due to the carbonate sorption on the solid surface [7]. Sorption of CO 2 onto the iron mineral surface sites possibly occurs, as supported by infrared measurement [8] of gas sorption, pH titration experiment [9], and zeta-potential measurement [7].…”

Section: Discussionmentioning

confidence: 99%

Sorption of actinides on magnetite and goethite under reducing conditions

2006

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The present study investigated the sorption of 237 Np, 239 Pu and 241 Am onto magnetite and goethite as a typical iron corrosion product under reducing conditions as a function of solution pH, both in the presence and absence of CO 2 at 25 °C. The sorption experiments were carried out for each actinide independently and for the simultaneous presence of the three actinides. Alpha-spectrometry of the liquid phase was performed to determine the equilibrium concentrations of the actinides after the sorption period. The sorption was strongly pH dependent. The sorption of 237 Np onto iron minerals was enhanced by the presence of CO 2 to some extent. In other cases, the presence of CO 2 did not affect or prevented the actinides from sorption. There seems to be no simple tendency in the observed data under the conditions examined, probably due to the effects of aqueous and surface complexation reactions with carbonate ions.

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Diffusion of Neptunium(V) in Loosely Compacted Sodium Bentonite

Cited by 7 publications

References 0 publications

Diffusion measurement of caesium in compacted bentonite

Diffusion measurement of caesium in compacted bentonite

Sorption and diffusion behaviours of strontium in sodium-type bentonite bed

Sorption of actinides on magnetite and goethite under reducing conditions

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