Impacts of Si on Se(IV) immobilization on ferrihydrite; An In-situ ATR-IR spectroscopic investigation

Francisco, P. C. M.  ; 舘 幸男  

Francisco, P. C. M.; Tachi, Yukio

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.