Synthesis Of Functional Mesoporous Silica Materials And Their Application Of Removing Heavy Metal Ions

Mesoporous SiO2materials emerge in1990s. Because they have very large specific surface area, thermal and physical stability, highly uniform pore distribution, tunable pore size, high adsorption capacity and high adsorption capacity, they are widely used in organic-inorganic separation, organic synthetic catalysis, environmental management and drug release, etc. Especially for their extraordinarily wide possibilities of organic functionalization, they can be probably used in a much more wide area. So they are materials with development value. In recent years, the water in the environment containing more and more organic and inorganic contaminants, these substances will pose a major health risk to humankind. Using absorbent remove pollutants is one of the methods of environment management. Mesoporous SiO2modified with organic reagent is one kind of the excellent absorbent. Compared with activated carbon and resin, the functional mesoporous SiO2have uniform structure, good stability, so they are likely to selectively remove the pollutant from the environment with high adsorption capacity. In general, they have good application value.Most of the previous reports are purpose of looking for new organic reagent to modify mesoporous SiO2materials, but few of them foucus on the modify method and process. In the research of preparing mesoporous SiO2, our work pays more attention to the optimization of the modification process and aims to put forward a kind of relatively safe and high grafting efficiency modify method. For study of metal ion adsorption, we pay more attention to adsorption capacity and selectivity. Specific contents are as follows:(1) The preparation of functional mesoporous SiO2materialsWith the sol-gel method, two different pathways including copolycondensation and two-step grafting were applied to prepare MCM-41and SBA-15functional mesoporous SiO2materials. Because the traditional method was time-waste, low efficiency and not environmental friendly, the concept of "green grafting" was introduced.(2) The optimization of the "green grafting" processAccording to nuclear reaction mechanism, potassium was used as the catalyst in the modification process. The environmental friendly ethanol was used to replace the toxic toluene solvent. The reagent proportion, reaction time and the kind of solvent were optimized. A green grafting method with low toxicity and high efficient was established.(3) The characterization of the materialsTo compare the copolycondensation and after grafting methods, scanning electron microscope, X-ray diffraction, Fourier Infrared Spectrum, nitrogen isothermal adsorption were applied to analyse the structure of the materials. Pore distribution and grafting efficiency were comprehensively analysed. To compare the traditional graft method and the green method, element analysis was used. The analysis result indicated that the green one possess the advantages of high efficiency and low energy consumption.(4) The study of heavy metal ion adsorptionThe prepared functional mesoporous SiO2materials were applied in the adsorption of metal ions with different valence and sizes. After absorption, the filtrate or eluent was determined by flame atomic absorption spectrometry(FAAS). The results shown that2-mercaptoben-zothiazole modified mesoporous SiO2was able to separate Cr(Ⅲ) with Pb (Ⅱ), Cu (Ⅱ) and Cd (Ⅱ). It had selective adsorption, high adsorption capacity, fast absorption rates and renewable ability.(5) The preparation of molecular imprinting mesoporous SiO2materials and their selectivity of Pb(Ⅱ)To remove common heavy metal ion lead from the water, molecular imprinting mesoporous SiO2materials were prepared by using lead ions as templates and using2-mercaptobenzothiazole modified mesoporous SiO2as monomer. The materials have highly selective adsorption ability of Pb(Ⅱ), out from Cu(Ⅱ) and Cd (Ⅱ). When they were used to separate and preconcentrate trace amount of lead ions in solution, it was found that the enrichment effect was excellent and it could reduce the detection limit of flame atomic absorption spectrometry method.