Preparation Of Mesoporous Silica And Its Adsorption Properties For Methylene Blue

Organic dye wastewater which is harmful to human health and environment,is difficult to be solved.Adsorption is widely used in the treatment of dye wastewater,because of its advantages of simplicity and efficiency,low cost and easy operation.Among the common adsorbents,mesoporous silica has many advantages,such as stable chemical properties,variety of preparation methods,low density,large specific surface area,continuous adjustable aperture,strong adsorption performance and multiple recycling.In this paper,mesoporous silica with different structures and morphologies was prepared by using tetraethyl orthosilicate and sodium metasilicate as silicon source,and amino-ended hyperbranched polyamide?AEHPA-n,n=1,2?as the template.Fourier transform infrared spectroscopy,X-ray diffraction transmission electron microscope and N₂ physical adsorption-desorption isotherms were employed to characterize the synthesized materials.The adsorption property of mesoporous SiO₂ in dealing with methylene blue in aqueous was investigated.The main research contents are as follows:?1?Disordered alveolate mesoporous silica materials with large specific surface area and narrow pore size distribution were prepared by using amino-ended hyperbranched polyamide as the template and tetraethyl orthosilicate?TEOS? as the silicon source.The effects of water and template dosages,reaction and crystallization temperatures and the molecular weight of the template on the properties of synthesized materials were discussed.Especially,one of the mesoporous silica materials named as AT-SiO₂-H1 which was synthesized under the condition of 4 g AEHPA-1,2 m L water,9 mL TEOS,reacting at 30? for 48 h and crystalizing at 80?for 24 h,exhibited BET surface area of 527.0m²/g,pore capacity of 0.45 cm³/g and pore size of 3.45 nm.?2?Disordered alveolate mesoporous silica materials with large specific surface area and narrow pore size distribution were prepared by using amino-ended hyperbranched polyamide as the template and Na₂SiO₃·9H₂O as the silicon source.The effects of the dosageand molecular weight of the template agent,the reaction temperature,and p H on the properties of synthesized materials were investigated.Especially,one of the mesoporous silica materials named as AN-SiO₂-A1Ta which was synthesized under the condition of0.06 g AEHPA-1,20 g Na₂SiO₃·9H₂O,60 mL water,p H=5-6,reacting at 30? for 2 h and ageing for 24 h at room temperature,exhibited BET surface area of 481.2 m²/g,pore capacity of 0.45 cm³/g and pore size of 3.75 nm.?3?The adsorption properties of the synthesized materials in dealing with methylene blue were investigated.The effects of p H,temperature and adsorbate concentration on the adsorption process were investigated.The results showed that all of the fresh materials exhibited excellent adsorption performance,but the absorptivity attenuated after 5 cycles,accompanying with the decreasing of BET surface area and broadening of the pore size distribution.The adsorptivity and regeneration ability of the synthesized materials using Na₂SiO₃·9H₂O as silicon source win out over that of the materials using TEOS as silicon source.Particularly,the maximum adsorption capacity of AN-SiO₂-A1Ta was 196.1 mg/g for 800 mg/L methylene blue solution?10?,pH=11,36 h?.For 300 mg/L methylene blue solution,the maximum adsorption capacity of fresh AN-SiO₂-A1Ta was 74.92 mg/g?10?,pH=11,3h?,and still reached 74.11 mg/g even after the material was used continuously five times.