Abstract
In-situ oxidation of solid phase was considered to investigate adsorption behavior under different geochemical parameters like pH, initial concentration and ionic strength. Pumice tuff, a potential host rock for low and intermediate radioactive wastes, has been affected by the redox zone. The characterization of the fresh and oxidized tuff was performed by X-ray diffractometer, scanning electron microscope and mercury intrusion porosimetry. In order to compare the difference of distribution coefficient (Kd) in fresh and oxidized pumice tuffs, a batch adsorption study was carried out at the range of pH (4 - 12), ionic strength (0.003, 0.1, 1.0 and 3.0 mol/dm3) and initial cesium concentration (10dž, 10LJ, 10Lj and 10lj mol/dm3). Based on experimental Kd values, ionic strength was found to be the most influential factor, whereas the effects of pH, initial Cs concentration and weathering condition of pumice tuff were negligible. The recalculated Kd values suggest that the existing surface complexation model is applicable to explain the sorption coefficients through the wide range of solution conditions.
Highlights
Reduction phenomena of bed rock in the vicinity of waste repository by contacting the surface/subsurface waterHow to cite this paper: Rajib, M., Kobayashi, T., Oguchi, C.T. and Sasaki, T. (2016) Oxidation of Solid Phase and Ionic Strength Effect to the Cesium Adsorption on Pumice Tuff
This study presents wider variation of geochemical parameters like initial Cs concentration of 10−4, 10−5, 10−6, 10−7 mol/dm3 (M), pH of 4 to 12 and ionic strength of 0, 0.1, 1.0 and 3.0 M NaClO4
The physical properties provide the differences in oxidation condition of the pumice tuff (Figure 2)
Summary
Reduction phenomena of bed rock in the vicinity of waste repository by contacting the surface/subsurface waterHow to cite this paper: Rajib, M., Kobayashi, T., Oguchi, C.T. and Sasaki, T. (2016) Oxidation of Solid Phase and Ionic Strength Effect to the Cesium Adsorption on Pumice Tuff. There can be anthropogenic processes too, through access of air into man-made excavations when oxidation occurs to previously reduced minerals by oxidizing air and/or water that diffuse(s) from the galleries into the matrix of the surrounding rock [6]. This zone may have significant effect on the adsorption of certain nuclides [7], long-term chemical stability [8], and control the mobilization and fixation of many trace elements, including potential pollutants that can be released from the wastes [9]. For any proper safety assessment for a deep geological repository, such long-term redox processes in the geosphere surrounding the repository need to be taken into account adequately [6]
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