Diffusion and retention behaviour of Cs in illite-added compacted montmorillonite

Abstract

Compacted bentonite is to be used as a component of an engineered barrier system to retard the migration of radionuclides in the geological disposal of radioactive waste. In such an environment, montmorillonite in compacted bentonite might be altered to illite due to the hydrothermal reactions caused by the decay heat of radionuclides. In the present study, the diffusion and retention behaviour of Cs in compacted montmorillonite containing illitewas investigated using through-diffusion experiments. The experimental results showed that the flux of Cs attributed to the surface diffusion was independent of the sorption of Cs on illite, indicating that the Cs sorbed on illite was immobile or considerably less mobile than the Cs sorbed on montmorillonite. Consequently, the illite content in compacted bentonite is expected to enhance the sorption capacity of Cs without causing surface diffusion.

A structural coarse-grained model for clays using simple iterative Boltzmann inversion

“…Because of its ability to selectively exchange radiocesium, illite and similar clays have been investigated for the possibility of remediating radioactive plumes of cesium. 10 Despite extensive experimental study of ion adsorption at the frayed clay edge and exchange of ions in the clay interlayer [7][8][11][12][13] , the exact mechanism of cesium uptake remains elusive. 14 It is especially unclear how cesium displaces potassium within the interlayer far from the edge in anhydrous interlayers for clays such as illite 11,[15][16][17] .…”