Radiation modification of mesoporous SiO2 and its adsorption performance for rhenium

In this study, poly 4-vinylpyridine-modified multilayered mesoporous silica (FS-VP) was synthesized by radiation grafting, and the effects of the synthesis conditions on the grafting ratio were investigated. The results of Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) indicated that the grafting ratio of FS-VP reached the maximum value of 27.8% under the following conditions: 4-vinylpyridine (4-VP) monomer concentration, 50%; radiation dose rate, 3 kGy/h; and absorbed dose, 72 kGy. In addition, quaternized FS-VP (FS-VPQ) was prepared, and its adsorption performance for Re(VII) was also studied. The adsorption capacities were the maximum at pH 2 and 3. The adsorption isotherm of FS-VPQ for Re(VII) conformed to the Langmuir model. The saturated adsorption capacity reached 68.0 mg/g at pH 3. The high adsorption capacity was attributed to the high specific surface area of the multilayered pore structure and the two inherent positive charges of the adsorbent after quaternization. Moreover, due to the high mass transfer rate resulting from the multilayered pore structure, FS-VPQ reached adsorption equilibrium within 3 min. The findings of this study provide theoretical guidance for Re separation and enrichment technology, and also can serve as reference for the separation of Tc from radioactive waste liquids.