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

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)

Abstract

The apparent diffusivities (Da) and activation enthalpies (ΔEa) for I- and Cs+ ions in compacted Na-smectite were obtained in the parallel and perpendicular directions to the orientation of smectite particles as a function of smectite's dry density (0.9-1.4 Mg/m3), salinity ([NaCl]=0.01, 0.51 M) and temperature (295-333 K). The Da-values for both ions tended to be higher in the parallel direction than in the perpendicular direction to the orientation of smectite particles. The Da-values off I- ions in the parallel direction decreased with increasing salinity only at low dry density, but those of Cs+ ions increased with increasing salinity for all conditions. Based on this, it is interpreted that I- ions predominantly diffuse in external pores and Cs+ ions diffuse in both interlayer and external pores. The ΔEa-values for I ions are at similar levels as those for the ionic diffusivity in free water (D o) of I- ions at low dry density and increased with increasing dry density. The ΔEa-values for Cs+ ions are higher than those for the Do of Cs+ ions even at low dry density and increased with increasing dry density. Such high ΔE a-values for Cs+ ions are considered to be due to the combined effects of the ion exchange enthalpy between Cs+ and Na + ions in smectite and the lowering in the activity of porewater.

Original languageEnglish
Title of host publication29th International Symposium on the Scientific Basis for Nuclear Waste Management XXIX
PublisherMaterials Research Society
Pages905-912
Number of pages8
ISBN (Print)1558998896, 9781558998896
DOIs
Publication statusPublished - 2006
Externally publishedYes
Event29th International Symposium on the Scientific Basis for Nuclear Waste Management XXIX - Ghent, Belgium
Duration: Sep 12 2005Sep 16 2005

Publication series

NameMaterials Research Society Symposium Proceedings
Volume932
ISSN (Print)0272-9172

Other

Other29th International Symposium on the Scientific Basis for Nuclear Waste Management XXIX
CountryBelgium
CityGhent
Period9/12/059/16/05

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Fingerprint Dive into the research topics of 'Effects of the orientation of clay particles and ionic strength on diffusion and activation enthalpies of i<sup>-</sup> and Cs<sup>+</sup> ions in compacted bentonite (II)'. Together they form a unique fingerprint.

Cite this