Study On The Synthesis Of Functionalized Mesoporous Silica Materials And Adsorption Properties

By the use of self-assembled surfactant molecular aggregates as the structure directing agents, Scientists reported the synthesis of M41S and SBA-15mesoporous materials with uniform pore size, high surface areas and pore volumes. These materials have already attracted considerable attention in the areas such as adsorption, separation, catalysis, biosensors and fabrication of noel nano-sturctures because of their adjustable pore sizes and dimensions, easily to vary surface functional groups and skeleton elements according to the actual application requirement, designable morphologies(film, fiber, sphere, etc.). There are many routes can obtain M41S materials, but lacking a simple and effective way to achieveing the transition between different phases.This way, to the theoretical research and practical application, it is important to find new type of templates, investigate the relationship between the structure of surfactant and the property of resulted mesoporous materials, and synthesize novel functionalized mesoporous materials, these studies have been hot areas of material research.In Chapter2, on the basis of the traditional hydrothermal synthetic method, a series of meoporous silica materials with different structures have successfully been synthesized with the using of environmentally friendly surfactant alkyl poly-glycoside(APG) as co-surfactant. These processes are depending on the concepts of surfactant science, sol-gel chemistry and supramolecular self-assembly. Many modern characterizations have been used to analyze the structure of these materials. By varying the stirring temperature, the chain length and concentrations of APG, we have synthesized mesoporous materials with different structures(cubic, hexagonal, lamellar). Through these simple way, the transform between different meso-phase structure have been studied systematically in this paper. APG is no pollution to the environment and has been mass industrial production, it can contribute great forces to the application of mesoporous materials.In Chapter3, we chose SBA-15and MCM-41as typical materials, further study the addition of APG in the synthesis of mesoporous materials. We find that whether under acid conditions or basic conditions, in certain range of APG, the pore properties can be regulate and control. During the synthesis of SBA-15, because of the hydrophilic and hydrophobic parts of APG are smaller than triblock copolymer, the addition of APG has no obvious influence on the structures. When change the ratio of APG12-14/P123from0to20, the BET surface area increases from322.96m2/g to518.44m2/g, the pore volume increases from 0.59cm3/g to0.94cm3/g, and the thickness of the pore wall decreases form4.77nm to3.22nm.On the contrary, the pore sizes nearly do not change.On the other hand, the carbon chain length of APG and CTAB are close by, the influence on MCM-41structure is greatly comparing with SBA-15. Under a small range of APG12-14/CTAB, we have synthesized relative regularly MCM-41materials with controllable pore properties. Adjusting the APG12-14/CTAB from0to0.5, the BET surface area increases from656.92m2/g to805.38m2/g, the pore volume increases from0.59cm3/g to0.87cm3/g, and the pore size increases from2.46nm to3.5nm, the thickness of the pore wall decreases form1.78nm to1.52nm. Excess APG12-14causes the defects on the MCM-41meso-structure, which eventually obtained amorphous silica materials.Compared with other mesoporous silica materials, the synthesis process of MCM-41is simpler. In chapter4, we have extended the magnetic functionalization of MCM-41. By using microemulsion method, cobalt ferrite nanoparticles are encapsulated in MCM-41which can avoid blocking the pore.By this method, the composite materials can be separated by external magnetic field. The pore size of composite material is3.46nm with a high surface area(829.81m2/g) and pore volume(0.90cm3/g). Composite material exhibits excellent magnetic properties with aturation magnetization (Ms,3.27emu/g) and high coercivty (Hc,252.13G). In this chapter, we use this composite in the removal of uranyl ion in water. The optimum pH for the adsorption was6and removal rates can reach89%under room temperature. With the studying of the adsorption isotherm data, the maximum adsorption capacity is213.68mg/g.