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杉浦 佑樹; 石寺 孝充; 舘 幸男
no journal, ,
We measured the sorption of Ca and its competitive sorption with Sr and Ni at high pH and ionic strength conditions. Sorption data were then evaluated using a thermodynamic sorption model. values of Ca increased with increasing pH values in alkaline pH region and the tendency was more pronounced at high ionic strength, indicating sorption onto edge sites. Fitting analyses show that Ca sorbs onto SOH sites, with CaOH sorption onto planar sites contributing at high alkaline pH regions. In competitive sorption experiments, Sr sorption onto the edge site decreased with increasing Ca concentration. In contrast, Ni sorption onto the edge site was independent of Ca. These results indicate that Sr sorbs onto the same edge sites (SOH) as Ca, while Ni sorbs onto different edge sites (SOH). Model calculations using the obtained sorption parameters reproduce the results of competitive sorption experiments.
Francisco, P. C. M.; 舘 幸男
no journal, ,
The long-lived Se-79 is one of the key radionuclides of interest in radioactive waste management due to its long half-life and radiologic and chemical toxicity. The migration of the highly mobile Se(IV) species may be mitigated with iron phases present in the disposal environment. However, the presence of Si derived from the clay buffer or host rocks may interfere with the sorption and retention of Se(IV) on iron phases. In this work, we conducted in situ ATR-IR to investigate the interaction of Se(IV) and Si with the surface of ferrihydrite, a poorly crystalline iron phase. We observed that Si reduces the sorption of Se(IV) on ferrihydrite and promotes its remobilization by blocking sorption sites. This impact of Si on Se(IV) sorption must then be taken into account in modeling studies for the safety assessment of radioactive waste repositories.