The sorption behavior and microscopic sequestration mechanisms of radionuclide 63Ni（II） on mordenite as a function of aging time, ionic srength, initial 63Ni（II） concentrations, solid content and coexistent electr...The sorption behavior and microscopic sequestration mechanisms of radionuclide 63Ni（II） on mordenite as a function of aging time, ionic srength, initial 63Ni（II） concentrations, solid content and coexistent electrolyte ions were investigated by the combination of batch and EXAFS techniques. Macroscopic experiment results show that the sorption of 63Ni（II） is dependent on ionic strength at pH〈7, and independent of ionic strength at pH〉7. The sorption percentage of 63Ni（II） on mordenite increases with increasing solid content, while the sorption capacity decreases as solid content increases. The presence of different electrolyte ions can enhance or inhibit the sorption of Ni（II） on mordenite in various degrees. EXAFS analysis results of the sam- ples under three different ionic strengths suggest that the retained 63Ni（II） in these samples exists in an octahedral environment with six water ligands. In the initial period of rapid uptake, the sorption of 63Ni（II） is dominated by the formation of innersphere surface complexes. As aging time increases, 63Ni（II） sequestration behavior tends to be mainly controlled by the formation of Ni phyllosilicate coprecipitates and/or Ni（OH）2（s） precipitates. Results for the second shell fit of the sample prepared at an initial 63Ni（II） concentration of 100 mg/L indicate the possible formation of Ni polynuclear surface complexes. Both the macroscopic sorption data and the molecular level evidence of 63Ni（II） surface speciation at the mordenite/water interfaces should be factored into better predictions of the mobility and bioavailability of 63Ni（II） in environment mediums.展开更多
基金supported by the National Natural Science Foundation of China (20907055,20971126 & 21077107)the National Basic Research Program of China (2011CB933700)the Knowledge Innovation Program of CAS and Special Foundation for High-level Waste Disposal (2007-840)
文摘The sorption behavior and microscopic sequestration mechanisms of radionuclide 63Ni（II） on mordenite as a function of aging time, ionic srength, initial 63Ni（II） concentrations, solid content and coexistent electrolyte ions were investigated by the combination of batch and EXAFS techniques. Macroscopic experiment results show that the sorption of 63Ni（II） is dependent on ionic strength at pH〈7, and independent of ionic strength at pH〉7. The sorption percentage of 63Ni（II） on mordenite increases with increasing solid content, while the sorption capacity decreases as solid content increases. The presence of different electrolyte ions can enhance or inhibit the sorption of Ni（II） on mordenite in various degrees. EXAFS analysis results of the sam- ples under three different ionic strengths suggest that the retained 63Ni（II） in these samples exists in an octahedral environment with six water ligands. In the initial period of rapid uptake, the sorption of 63Ni（II） is dominated by the formation of innersphere surface complexes. As aging time increases, 63Ni（II） sequestration behavior tends to be mainly controlled by the formation of Ni phyllosilicate coprecipitates and/or Ni（OH）2（s） precipitates. Results for the second shell fit of the sample prepared at an initial 63Ni（II） concentration of 100 mg/L indicate the possible formation of Ni polynuclear surface complexes. Both the macroscopic sorption data and the molecular level evidence of 63Ni（II） surface speciation at the mordenite/water interfaces should be factored into better predictions of the mobility and bioavailability of 63Ni（II） in environment mediums.
