Preparation Of Of Porous Composite Aerogels And Study On The Adsorption Of Ce(Ⅳ) Ions

The radioactive waste and its high-level liquid waste(HLLW) has become one of the key factors related to nuclear industry development, for nuclear fuel reprocessing and its treatment and disposal of HLLW, due to their highly radioactive properties and the tendency for bio-accumulation through the food chain. Plutonium(Pu) presents a long-term management problem and a serious security issue. The first principle of HLLW treatment is volume reduction and the second principle is minimizing secondary pollution. Among the conventional disposal routes of nuclear waste, the adsorption process is considered as one of the most economical and safe approaches due to its processes can offer high efficiency, low cost and high flexibility in design and operation. Since liquid is the most difficult and dangerous waste form due to its liquidity, removal of Pu from HLLW by adsorption process, late for deep geological disposal has far-reaching significance. This method can realize the change of the radioactive waste from liquid to solid directly, reduce processing costs, reduce volume effectively and avoid secondary pollution 。 Essentially, it is desirable to find an efficient and economical SiO2/TiO2 composite adsorbent for the nuclear waste, which has many advantages like low cost, simple preparation process, high adsorption capacity and adsorption selectivity after chemical modification.In this paper, porous SiO2/TiO2 aerogels with multi-level channel structure and large pore volume was synthesized via sol-gel process with phase separation using TEOS and TnBT as raw materials. With the solvent replacement technique, SiO2/TiO2 aerogels were prepared via an ambient pressure drying process, and further grafted sulfonic group and other functional groups. The microstructure of the prepared porous composite aerogels were characterized by XRD, FT-IR, BET, SEM and so on. And the adsorption process of Ce(IV) (cerium) simulating Pu(IV) ions by the synthesized composite aerogels was described under different sorption conditions(T, t, adsorbate and adsorbent content). Preparation study shows that the morphology of porous aerogels and the size of the interconnected pores can be controlled by adjusting the compositions; the adsorption capacity and adsorption selectivity of aerogel adsorbent can be improved through grafting functional groups. The multilevel pore structure makes composite powders have higher specific surface area (1000.5 m2/g) and narrow pore size distribution (3-4.5 nm). The maximum adsorption capacities of Ce(IV) is 229.98 mg/g. Adsorption research demonstrates that the Ce(IV) sorption on composite aerogels is an endothermic and spontaneous process which could be well simulated by the pseudo-second-order kinetic equation.Using SiO2 aerogel with high-level liquid waste directly will cause a loss of powder which is difficult to recycle and lead to secondary pollution. And perfluorinated sulfonic acid resin (PSR) has good mechanical properties, SiO2 aerogel powder was enshrouded and hard to break away so that the radioactive powders can be recycled. It really has better environmental and economic benefits. Si02/perfluorosulfonated resin (SiO2/PSR) composite solution were prepared by ultrasonic wave technique with PSR as the carrier and modifier, and SiO2/PSR hybrid films were formed by flow casting. The dual effect of metal ions,including physical adsorption and ion exchange were finally achieved. The adsorption process of Ce(Ⅳ) simulating Pu(Ⅳ) ions by the synthesized SiO2/PSR hybrid films is studied. The results showed that when the mass fraction of SiO2 reached 15%, the hybrid film showed best adsorption properties. Sorption of 87.67% Ce(IV) to the SiO2/PSR hybrid films adsorbent were fulfilled in less than 10 h, which provides an innovative technology in treatment of HLLW.