Diffusion of 137Cs in compacted bentonite:: Effect of pH and concentration

The effect of pH and concentration on the diffusion of Cs-137 in the compacted bentonite is studied with capillary method at the ionic strength of 0.1M NaClO4. The apparent diffusion coefficient increases with increasing concentrations if the sorption of radionuclides is largely dependent on the radionuclide concentrations. The apparent diffusion coefficient decreases with increasing pH because most of the radionuclide sorption on the bentonite increases with increasing pH. The interlaminary space contributes significantly to the radionuclide diffusion and sorption in compacted bentonite. The relationship of the apparent diffusion coefficient and the effective diffusion coefficient of Cs-137 is also discussed.