Research Mesoporous Silica Fume Silica

Compared with the traditional porous materials, mesoporous materials have special properties, such as large specific surface areas, hydrothermal stability and ordered porous with tunable diameters at range of2～50nm and so on, affording huge potential applications in adsorption, catalysis and biomedical field. To date, great progresses have been made in recipes of high-quality mesoporous materials, and studies of mesoporous materials are mainly focused on the preparation of low cost. It will make great sense for cheap mesoporous silica materials used as adsorbent in the treatment of waste water. On the other hand, because of the lack of classification technology, silica fume cannot be used effectively and efficiently, and it is another hot spot of research to find a way for efficient usage of silica fume. The study integrated backgrounds both of mesoporous silica materials and silica fume industry as above, using silica fume as raw materials, synthesized MCM-41materials at low cost and applied it in the adsorption of heavy metal ions, in the hope of preparation of adsorbents economically, providing resolutions for reasonable applications of silica fume at the same time.Silicon fume is mainly amorphous silica compositied with with spherical morphology of nanometer range. Based on the the existing recipes and combined with the nature of the micro silicon powder, it went with roasting pretreatment of micro silicon powder firstly, to remove the volatile impurities in the raw silicon fume, and preparation of mesoporous silica by different methods sbsquently:(1) One-stage synthesis of spherical mesoporous silicaWith small-amount base used, the spherical morpholoy of silicon fume will not be destroyed. Cetyltrimethyl Ammonium Bromide (CTAB) and polyethylene glycol (PEG-6000) were used as template agent,and silicon fume as silicon source. Basic liquid premeated into the silicon fume spheres, and synthesis worked out from the surface to the core in a way of Pseudomorphic Transformation, with spherical mesoporous silica materials prepared;(2) Two-stage synthesis of mesoporous silicaUnder high alkalinity, silicon fume will be completely dissolved into solution. In alkaline environment, dissolved silicate from dissolution in body reacted with CTAB and PEG through electrostatic attraction. Under acid condition, deposition, aggregation, and transformation of organic and inorganic phase were compeleted, and so was the nucleation and growth along the different interface of the mesoscopic phase. In the end, mesoporous silica materials of ordered channels and different morphology were acheived;This test using the X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), projection electron microscope (TEM), N2adsorption stripping curve, testing method (BET) surface area testing means, the raw material, and after the experiment sample structure, morphology and synthetic mechanism, and through the static adsorption of heavy metal ion solution test, the product of adsorption performance to do the research. Through the analysis of experimental results, discusses the material ratio, temperature, time, acid type etc. The impact on the product structure and performance, the optimum process conditions of different process is obtained.Through the methods of the X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), projection electron microscope (TEM), N2adsorption-desorption stripping curve and surface area testing means(BET), product morphology and synthetic mechanism were studied. Through the static adsorption experiment of heavy metal ion solution, we analyzed the adsorption property of the synthesized MCM-41. On the base of experimental results, we discussed influencing factors such as the material ratios, temperature, time and acid types, and the optimum process conditions of different methods are obtained.With silica fume used, MCM-41materials of different morphology, such as ball, flake and core-shell ball, were synthesized successfully. All products showed good adsorption performance, and the maximum adsorption capacity were74.5g/mg,36.5mg/g and36.5g/mg for Pb2+and Cd2+, Cu2+respectively. Adsorption of MCM-41matreials for heavy metal ions conforms to the Langmuir model.