Preparation Of Crystallization Mesoporous Silica And Structure Characterization

Silicate materials have excellent properties are widely used in adsorption owing to their stability, environmentally benign nature.In particular, magnesium silicate nanomaterials can be used as a highly efficient adsorbent to adsorb heavy metal ions, radioactive isotopes and organic pollutants.For adsorption, high specific surface area and porous structures are two critical features that enhance the interaction between the pollutants and adsorption sites for high adsorption capacities.Therefore,most work on magnesium silicates focus on preparing hollow structures in the past few years. Compared to magnesium silicate hollow nanospheres, mesoporous magnesium silicate have better hydrothermal stability and shorter transportation path, and are thereby more suitable for adsorption. However, synthesizing mesoporous magnesium silicate has rarely been reported.In this thesis, mesoporous magnesium silicate was prepared by sacrifice auxiliary template- hydrothermal method using mesoporous silica SBA-15 filled with carbon (C@SBA-15) as both assisted template and silica source. During the hydrothermal process, the silica of the C@SBA-15 reacts with magnesium ions to form magnesium silicate.Meanwhile, the carbon inside the pores of mesoporous silica SBA-15 supports the formed magnesium silicate as mesoporous walls under hydrothermal condition. The mesoporous magnesium silicate crystallization has been obtained after removing the carbon by calcinations.The crystal structure and mesostructure were investigated by X-ray diffraction (XRD) on a PANalytical Empyrean diffractometer with Cu Ka radiation. The morphology and microstructure were characterized by a Hitachi S-4800 scanning electron microscopy (SEM) and FEI Tecnai F20 transmission electron microscopy (TEM), respectively. N2 adsorption-desorption isotherms were measured with a Micromeritics ASAP2020 specific surface area analyzer. The mesoporous magnesium silicate possesses a two-dimensional hexagonal mesostructure, large specific surface area, and high thermal stability. Such features would be beneficial for enhancing the adsorption performance.Through research the adsorption of Pb2+ and methylene blue with crystallization mesoporous magnesium silicate as adsorbents, respectively. The crystallization mesoporous magnesium silicate has a good adsorption performance, can be widely used for heavy metal ions in sewage treatment. The study shows that use C@SBA-15 and magnesium salt as raw material to synthesis new tapes of mesoporous magnesium silicate has a larger specific surface area, has good adsorption for the pollutants in water and regeneration characteristics, can be reused. The new synthetic route not only offers more possibilities for the preparation of new mesoporous silicate materials, and can better improve the adsorption efficiency of magnesium silicate as adsorbent.