Effects of the orientation of clay particles and ionic strength on diffusion and activation enthalpies of I- and Cs+ ions in compacted bentonite

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Abstract

Apparent diffusivities (Da) for I- and Cs+ in compacted Na-smectite were studied as a function of smectite's dry density (0.9-1.4 Mg/m3), ionic strength (IS: [NaCl]=0.01, 0.51 M), temperature (22-60°C) and diffusion direction to the orientated direction of smectite particles. The Da-values for both ions in parallel direction to the orientated direction showed a tendency to be higher than those in the perpendicular direction at low IS. The Da-values for I- showed different trends depending on diffusion direction and dry density at high IS, but Da-values for Cs+ increased with increasing IS in both diffusion directions. The activation enthalpies (ΔEa) for I-, slightly higher than that of diffusivity in free water (Do) at low IS, similar level to that of Do at high IS, increased with increasing dry density. While, ΔEa-values for Cs+, clearly higher than that of Do for all conditions, increased with increasing dry density. Since it is known that interlayer distance depends on both dry density and IS, diffusive pathway is considered to differ depending on the charge of diffusion species.

Original languageEnglish
Title of host publicationMaterials Research Society Symposium Proceedings
EditorsJ.M. Hanchar, S. Stroes-Gascoyne, L. Browning
Pages485-490
Number of pages6
Volume824
Publication statusPublished - 2004
Externally publishedYes
EventScientific Basis for Nuclear Waste Management XXVIII - San Francisco, CA, United States
Duration: Apr 13 2004Apr 16 2004

Other

OtherScientific Basis for Nuclear Waste Management XXVIII
CountryUnited States
CitySan Francisco, CA
Period4/13/044/16/04

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials

Cite this

Sato, H. (2004). Effects of the orientation of clay particles and ionic strength on diffusion and activation enthalpies of I- and Cs+ ions in compacted bentonite. In J. M. Hanchar, S. Stroes-Gascoyne, & L. Browning (Eds.), Materials Research Society Symposium Proceedings (Vol. 824, pp. 485-490). [CC8.46]