Anisotropy and Effect of Salinity in Diffusion and Activation Energies of Cations and Anions in Compacted Bentonite

Sato, Haruo

The anisotropy and effect of salinity in the apparent diffusion coefficients (Da) and activation energies (Ea) for I- and Cs+ ions were studied. The diffusion experiments were carried out as a function of smectit's dry density, salinity, temperature and diffusion direction to the orinentated direction of smectite particles. An purified Na-smectite was used in the experiments. I- Ions are considered to mainly diffuse in interstitial pores and Cs+ ions are considered to diffuse in both interlayer and interstitial pores from the changes of the Da- and Ea-values for both ions on dry density, salinity and diffusion direction. Moreover, I- ions are considered to be affected by electrostatic effect from smectite surface, and Cs+ ions are considered to the effect of the decrease in the activity of porewater in addition to the effect of ion exchange enthalpy between Cs+ and I- ions in smectite.