Diffusion and Migration of Ions in Sedimentary Rock Matrix: Behaviour of Cesium and Iodide in Micropores of Sandstone

Abstract

In-diffusion experiments for Cs + and I -in sandstone were performed as a function of ionic strength of porewater ([NaCl]=0.01, 0.51M) and tracer concentration ([CsI]=7.5E-5, 1.5E-2M) together with the measurements of the fundamental properties of sandstone, and apparent diffusivities (Da) and rock capacity factors (α) for Cs + were obtained. The obtained Da-values for Cs + were scarcely dependent on [NaCl], but increased with increasing [Cs + ]. This trend is consistent with that of α-values, indicating that although effective diffusivity and distribution coefficient scarcely depend on [NaCl], those depend on [Cs + ]. The concentration profiles of I -were all in breakthrough. Although this indicates that I -diffusion is faster than that of Cs + , the concentration profiles of I -may have been lower than those for blank samples.

Measurements on the Thermodynamic Properties of Porewater in Sandstone by Vapor Pressure Method

“…This indicates that about 20% of the porewater is weakly affected from the solid surface, while 7% of the porewater is more strongly affected from the solid surface. This is in relatively good agreement with the estimated results 11) for the region that affects the viscosity of porewater influenced by electrostatic attraction on the surface of quartz. This region in porewater influenced by the solid surface is larger for sandstone than for montmorillonite, [2][3][4]8) which is in agreement with earlier predictions.…”

Measurements on the Thermodynamic Properties of Porewater in Sandstone by Vapor Pressure Method

“…10) The physical and chemical properties of the sandstone are already published in previous studies. [11][12][13][14] Table 1 shows the physical and chemical properties of the sandstone specimens used in this work. Porosity is 15.6% from both results of water saturation and Hg intrusion measurements.…”