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 a...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 (K<sub>d</sub>) 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/dm<sup>3</sup>) and initial cesium concentration (10<sup>dž</sup>, 10<sup>LJ</sup>, 10<sup>Lj</sup> and 10<sup>lj</sup> mol/dm<sup>3</sup>). Based on experimental K<sub>d</sub> 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 K<sub>d</sub> values suggest that the existing surface complexation model is applicable to explain the sorption coefficients through the wide range of solution conditions.展开更多
This study examines the use of intact samples as an alternative to powder in conventional batch sorption studies to determine the distribution coefficient(K_d).Stable cesium(^(133)Cs) and strontium(^(87)Sr) were used ...This study examines the use of intact samples as an alternative to powder in conventional batch sorption studies to determine the distribution coefficient(K_d).Stable cesium(^(133)Cs) and strontium(^(87)Sr) were used under specified geochemical conditions to compare the Kdvalues of powder and block pumice tuff samples. The aim of the study was to infer any Kddifference under laboratory and field conditions. Kdvalues for block samples were found to be less than one order of magnitude lower than powder materials for both Cs and Sr on fresh tuff, and more than one order of magnitude lower in oxidized tuff. Destruction of micropores in oxidized tuff was estimated to be mainly responsible for reducing Kdvalues in oxidized tuff. However, approximately one order of magnitude difference in Kdvalues indicates that homogenously prepared intact samples can be used for sorption coefficient measurement at closer to in situ conditions. Pore size distribution analysis using mercury intrusion porosimetry revealed that lower Kdvalues on block samples result from lower surface area available as sorption sites due to inaccessible closed pores in the intact solid.展开更多
文摘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 (K<sub>d</sub>) 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/dm<sup>3</sup>) and initial cesium concentration (10<sup>dž</sup>, 10<sup>LJ</sup>, 10<sup>Lj</sup> and 10<sup>lj</sup> mol/dm<sup>3</sup>). Based on experimental K<sub>d</sub> 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 K<sub>d</sub> values suggest that the existing surface complexation model is applicable to explain the sorption coefficients through the wide range of solution conditions.
文摘This study examines the use of intact samples as an alternative to powder in conventional batch sorption studies to determine the distribution coefficient(K_d).Stable cesium(^(133)Cs) and strontium(^(87)Sr) were used under specified geochemical conditions to compare the Kdvalues of powder and block pumice tuff samples. The aim of the study was to infer any Kddifference under laboratory and field conditions. Kdvalues for block samples were found to be less than one order of magnitude lower than powder materials for both Cs and Sr on fresh tuff, and more than one order of magnitude lower in oxidized tuff. Destruction of micropores in oxidized tuff was estimated to be mainly responsible for reducing Kdvalues in oxidized tuff. However, approximately one order of magnitude difference in Kdvalues indicates that homogenously prepared intact samples can be used for sorption coefficient measurement at closer to in situ conditions. Pore size distribution analysis using mercury intrusion porosimetry revealed that lower Kdvalues on block samples result from lower surface area available as sorption sites due to inaccessible closed pores in the intact solid.