Study On The Sorption Of U(Ⅵ) And Th(Ⅳ)on The Mesoporous Silicas And The Modified Materials

Mesoporous materials with two different structures (MCM-48and MCM-41)were synthesized by a hydrothermal method and using tetraethylorthosilicate (TEOS), cetyltrimethylammonium bromide (CTAB) as the silica source and temples, respectively. And MCM-48was modified by saturated impregnated method to achieve polyoxometalates load on the MCM-48,and finally get the polyoxometalate supported mesoporous materials successfully; Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD) analysis, N2adsorption-desorption isotherms and thermal gravimetric analysis are used to characterize the chemical composition, surface physical and chemical properties and thermal stability of the synthesized material,the results show that:the synthesised MCM-48and MCM-41have its own mesoporous structure regularly and orderly, and the pore size distribution is narrow and uniform. Polyoxometalates supported mesoporous materials and MCM-48have similar mesoporous structure, but the specific surface area of it become smaller than that of MCM-48.In order to study the sorption behavior of Th(Ⅳ) and U(Ⅴ) on mesoporous silica. The batch sorption experiments are performed to examine the effect of contact time, pH, solid-to-liquid ratio, ionic strength and ambient temperature on the sorption.This study results show that:the sorption of Th (Ⅳ) and U (Ⅴ) on the synthesised mesoporous silica materials will achieve balance quickly, and the false second-order kinetic equation may be used to describe the sorption process;at the same time the sorpotion on the mesoporous materials is affected significantly by the system pH value and solid-to-liquid ratio, but the effect is relatively weak by the ionic strength, and can be ignored. We also found that the Langmuir model can describe the sorption behavior of U (VI) and Th (IV) on mesoporous silica material better.By comparing the sorption the properties of U(VI)on MCM-48and PW11/MCM-48,we found that:the sorption capacity of the modified mesoporous silica is about ten times higher than before modification.