| Plutonium presents a long-term management problem and a serious security issue. Removal of Pu from high-level liquid waste (HLLW) by adsorption process and its encapsulation for deep geological disposal is an important environment challenge. Essentially, it is desirable to find an efficient and economical adsorbent for the nuclear waste.In this paper, co-continuous macro-porous and meso-porous silica gels were prepared by methods of separation and supercritical drying, respectively. The microstructure of the prepared porous silica gels were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) spectra, thermogravimetry-differential thermal analysis (TG-DTA) measurements and scanning electron microscopy (SEM) and so on. And the adsorption process of Ce(IV) simulating Pu(IV) ions by the sythesized silica aerogels was discribed under different sorption conditions. Moreover, the immobilization of the adsorbed Ce(IV) was investigated, and the MCC-1 leaching test was performed at 90℃.Preparation study shows that the morphology of as-dried porous silica gels and the size of the interconnected pores can be controlled by adjusting the compositions. Adsorption research demonstrates that the Ce(IV) sorption on silica aerogels is an endothermic and spontaneous process which could be well simulated by the pseudo-second-order kinetic equation and Langmuir isotherm molder. The immobilization study shows that the effects of heat-treatments on leaching properties is significant. Further, the samples sintered at 1000℃has the favorable leaching resistant with the lowest numalized leaching rate (magnitude of 10"3 g/(m2·d)). |
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