Electrokinetic study of migration of anions, cations, and water in water-saturated compacted sodium montmorillonite

Shingo Tanaka, Natsuko Noda, Seichi Sato, Tamotsu Kozaki, Haruo Sato, Koichiro Hatanaka

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Electromigration studies of 36Cl ions and 22Na+ ions, and electro-osmosis of water traced with HTO and H218O were conducted with water-saturated compacted sodium montmorillonite having dry densities from 0.8 to 1.6 Mg/m3. The mobilities and dispersivities for each species were obtained from the apparent electromigration velocities and hydrodynamic dispersion coefficients, respectively. When corrected by water flow, the apparent diffusion coefficients of Cl ions obtained from the Einstein relation are in good agreement with the coefficients obtained from an earlier conventional diffusion experiment in the high dry densities (above 1.3 Mg/m3,). This result suggests that the migration pathways of Cl ions are nearly identical to those of water above 1.3 Mg/m3. The former diffusion coefficient is smaller than the latter in the low dry densities (below 1.3 Mg/m3), suggesting that Cl ions migrate in the region distant from the montmorillonite sheets. In contrast, for Na+ ions, the obtained Da values without water flow correction are in good agreement with conventional values at all dry densities. This suggests that Na+ ions migrate mainly in the interlayer and the vicinity of montmorillonite sheets. The dispersivities increase with increasing dry densities for all species. This corresponds to a geometrical complexity that increases with increasing dry density.

Original languageEnglish
Pages (from-to)454-462
Number of pages9
JournalJournal of Nuclear Science and Technology
Volume48
Issue number3
DOIs
Publication statusPublished - 2011
Externally publishedYes

Keywords

  • Anion exclusion
  • Bentonite
  • Diffusion
  • Dispersion
  • Dispersivity
  • Einstein relation
  • Electro-osmosis
  • Electrokinetics
  • Mobility
  • Montmorillonite

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering

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