Preparation And Adsorption Performance Of Silica Microspheres With Amino Groups

Due to the large specific surface area,big pore volume,uniform pore size and rich surface functional groups,the M41S mesoporous molecular sieves have attracted much attention after they had been successfully synthesized.However,the mesoporous molecular sieves have not been widely used,because their hydrothermal stability is worse and their traditional preparation methods are imperfect.For example,the spherical mesoporous silica materials could be successfully prepared using TEOS and mixed-surfactants,but the surfactant used in this method is expensive and the prepared silica particle size is small,this will restrict its application.This work studied the new process of preparing mesoporous silica microspheres with large particle size.The monodisperse ordered mesoporous silica microspheres were synthesized by a two-step method.The morphology is controlled in the first step and then the structure is reconstructed in the second step.Moreover,the prepared silica microspheres were characterized by DLS(dynamic light scattering),BET,XRD and SEM.The modified silica microspheres were used in removal of copper ion from aqueous solution.The article mainly included the following aspects.(1)The nano silica sol was prepared by sol-gel method using TESO as silica source.Effects of reaction temperature and the amount of ammonium hydroxide in the sol-gel process were investigated.A series of silica sol with different particle size(30 nm to 200 nm)were successfully prepared.(2)The monodisperse porous silica microspheres were prepared using silica sol as primary particle.Effects of pH value,the molar rate of formaldehyde and urea,stirring time,reaction temperature and the size of primary particle were investigated.When the reaction temperature was 40 ℃,the pH value was 1.8,the molar ratio was 1.25,the size of primary particle was 40 nm and the stirring time was 5 min,the monodisperse porous silica microspheres with diameter of 3.76 μm could be successfully synthesized.(3)The ordered mesoporous silica microspheres were prepared by pseudomorphic synthesis method using the porous silica as primary microspheres.The pseudomorphic synthesis method could transform amorphous silica microspheres into silica-surfactant mesostructures without changing the shape and size of the microspheres.Effects of reaction time,reaction temperature,the amount of sodium hydroxide and CTAB in the pseudomorphic synthesis process were investigated.We also studied the principles of the pseudomorphic synthesis method.The optimal parameters of synthesis conditions were listed as follows:the molar ratio of reagent was SiO2:NaOH:CTAB=1:0.4:0.1,the reaction temperature and reaction time were 125 ℃ and 10 h,respectively.The specific surface area of silica microspheres increased significant after the pseudomorphic synthesis process.(4)The prepared silica microspheres were modified by(3-Aminopropyl)triethoxysilane.The modified materials were used in removal of Cu2+ from aqueous solution and the adsorption capacity and reproducibility were investigated.The results indicate the porous and ordered mesoporous silica microspheres grafted with aminopropyl groups have rapid adsorption capacity and good reproducibility,and their maximum adsorption capacity were 18.731 mg/g and 28.265 mg/g,respectively.