| Aerogels are a kind of solid materials which consist of nanoparticles and have continuous network structure filling with gaseous dispersive medium,the porosity can be as high as 85%-95%.Because of its unique structure makes the aerogel has a high specific surface area,low density,low thermal conductivity and other characteristics,which makes it widely used in the fields of thermal,acoustics and catalysis science.Silica aerogel microspheres based on alkaline silica sol were synthesized using the emulsion method,sol-gel polymerization and ambient pressure drying.There morphology and physical properties were analyzed by using scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR)and the Brunauer-Emmett-Teller(BET)method.Through the previous experiments and the related theory of emulsion,we identify the compound emulsifier was span 80 and tween 80,the concentration of emulsifier is 0.30 g/m L.The water oil ratio,the ratio of emulsifier concentrations and the stirring speed influence of the morphology and the size of the aerogel microspheres were studied.The optimum water to oil ratio of 0.1-0.4 was determined,and the optimum stirring rate was 300-500r/min.The phase,hydrophobicity,structure of these aerogel microspheres were investigated by several experimental methods,such as X-ray diffraction(XRD),scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),specific surface area analyzer,pore size analyzer and so on.The result shows that the silica aerogel microspheres prepared by the experiment are amorphous form and hydrophobic,and the particle size distribution is between 5-20?m.The specific surface area of the aerogel prepared by this method is small,the maximum is 451 m2/g,pore size distribution concentrated in 20-40 nm.The silica aerogel microspheres were prepared by surface modification with mixed surface modifier.The effects of the ratio of TMCS/MTMS,TMCS/HMDSO and MTMS/HDMS,modification temperature and modification time on the density and specific surface area of aerogel microspheres were studied.The results show that the specific surface area of aerogel microspheres prepared by using the mixed surface modifier is better than that without surface modifier.The use of HMDSO/TMCS mixed surface modifier can obtain aerogel microspheres with higher specific surface area.When the content of TMCS is 60%,the density is 0.106 g/ cm,the specific surface area is 660.65 m2/g,the surface modification temperature is 60 °C at this time.It can also be seen that the pore size distribution of the modified aerogel microspheres is wider than that of the unmodified aerogels,which indicates that the modified aerogel can maintain the nanoporous structure of aerogel.Finally,using silica sol and(2-cyanoethyl)triethoxysilane as precursor was prepared by modified silica aerogel microspheres of cyano group,and then by amidoximation reaction,the amidoxime silica aerogel microspheres was prepared and its adsorption properties were studied.The results showed that the modified amidoxime silica-based aerosol microspheres have good adsorption properties to copper ions.And the equilibrium adsorption capacity reaches 68.94 mg/g after 10 h adsorption.Dsorption kinetic is simulated by pseudo-first order and pseudo-second order equations,related regression analysis results indicate pseudo-second order equation is more fitted to describe adsorption process,the correlation coefficient R2 was 0.9945.Besides,sothermal datas correlate well with Freundlich models,which indicates the adsorption mode is a combinatio of multilayer coverage.It was also found that the desorption rate reached 68.9% when the adsorption-desorption experiment was repeated four times,indicating that the material had good reproducibility. |
PDF Full Text Request