Synthesis Of Titanium/Aluminum Modified SBA-15 And Its Adsorption Performance For Glyphosate

Glyphosate is the most widely used herbicide,and water ecosystem is one of its important destinations.The adsorption method can effectively remove glyphosate in water.In this paper,SBA-15 and series of mesoporous materials Al-SBA-15,SBA-15-Ti and AlSBA-15-Ti doped with Al and Ti were prepared.Its structure and morphology were characterized by nitrogen adsorption and desorption,small angle X-ray diffraction,transmission electron microscopy,and nuclear magnetic resonance.The adsorption and regeneration properties of materials were studied,and the mechanism of adsorption process was preliminarily discussed.The main research contents are as follows :(1)Aluminum doped mesoporous silica material Al-SBA-15 was prepared by direct synthesis method.Taking SBA-15 as a reference,the effect of aluminum content on adsorption performance was investigated.SBA-15 can hardly adsorb glyphosate.The incorporation of aluminum can introduce acidic sites,change the acidic environment on the surface of SBA-15,and increase the surface potential,which is conducive to the adsorption of glyphosate.With the increase of aluminum content,the adsorption capacity of the material gradually increases.When the solution p H was 3,the maximum adsorption capacity of Al(0.9)-SBA-15(measured Al/Si molar ratio was 0.88)could reach 111.00mg/g.The adsorption process conforms to the pseudo-second-order kinetic model,and the adsorption equilibrium conforms to the Langmuir model.When the initial concentration of glyphosate(C0)was 100 mg/g,the process equilibrium time was 480 min,and the adsorption capacity of Al(0.9)-SBA-15 was 66.35 mg/g.After five adsorption-desorption cycles,the adsorption capacity remained at about 84% of the initial adsorption capacity.(2)A series of titanium doped mesoporous silica SBA-15-Ti were synthesized by post-grafting method.The loading of titanium did not change the ordering of SBA-15,but it could increase the surface potential of SBA-15.With the increase of titanium loading,the adsorption capacity of the material for glyphosate increased first and then decreased.When the solution p H was 2,the maximum adsorption capacity of SBA-15-Ti(17)(measured mass fraction of titanium was 17.29%)reached 121.3 mg/g.The adsorption process conforms to the pseudo-second-order kinetic model,and the adsorption equilibrium conforms to the Freundlich model.When C0 was 100 mg/g,the adsorption capacity of SBA-15-Ti(17)was 81.12 mg/g,and the equilibrium time was 240 min.After five adsorption-desorption cycles,the adsorption capacity could still be maintained at about 79% of the initial adsorption capacity.The incorporation of titanium significantly increased the adsorption rate of the material.(3)Al-SBA-15-Ti was prepared by post-grafting method using Al-SBA-15 with different Al/Si ratios as support,and the effect of Al/Si ratio on the adsorption performance of glyphosate was investigated.When the titanium content is constant,the adsorption capacity of the material for glyphosate increases first and then decreases with the increase of aluminum content.When the solution p H was 3,the maximum adsorption capacity of Al(0.5)-SBA-15-Ti(the molar ratio of aluminum to silicon was 0.41 and the mass fraction of titanium was 23.75%)was 100.56 mg/g.The adsorption process conforms to the pseudo-second-order kinetic model,and the adsorption equilibrium conforms to the Freundlich model.When C0 was 100 mg/g,the adsorption capacity of Al(0.5)-SBA-15-Ti was 68.42 mg/g,and the equilibrium time was 240 min.The adsorption rate was significantly faster than that of Al-SBA-15.After five adsorptiondesorption cycles,the adsorption capacity remained at about 89% of the initial adsorption capacity.