Synthesis Of Mesoporous Silica Functionalized With Amino Acid For Heavy Metal Adsorption From Aqueous Media

Mesoporous silica material SBA-15functionalized with amino acid wassynthesised in this thesis. The adsorption property of modified materials for heavymetal ions was furthermore researched.Mesoporous silica material SBA-15which has large pore size, high surfaceareas order and adjustable pore structure was synthesized by tetraethoxysilane (TEOS)precursors and triblock copolymer H(OCHCH)(OCH(CH)CH)(OCHCH))OH (P123)as templating agent. Highly ordered amino-functionalized mesoporous silica(NH2-SBA-15) had been directly modified by grafting3-aminopropyltriethoxysilane(APTES) on the surface of SBA-15. Then three kinds of organic-inorganic hybridmaterials were synthesized by introducing L-Methionine(Met), L-cysteine(Cys) andL-Histidine(His) into the mesoporous channel respectively by the post-graftingmethod. Consequently, we have noted the products obtained finally as Met-SBA-15,Cys-SBA-15and His-SBA-15.The structures, surface adsorption properties and pore sized distribution of thesynthesized materials SBA-15, NH2-SBA-15, Met-SBA-15, Cys-SBA-15andHis-SBA-15were successfully characterized by TEM, XRD, FT-IR, N2adsorption-desorption and thermo gravimetric analysis. The results indicated that theorganic groups were successfully anchored on the SBA-15surfaces, the ordering ofthe inorganic support was preserved during the chemical modifications and thematerials had better thermo stability. In addition, the adsorption experiments in abatch method for heavy ions of the amino acid-functionalized SBA-15had beenemployed to investigate the selective absorbability and adsorptive property by testingthe concentration of the heavy ions before and after. The factors which may influencethe efficiency of the adsorption, such as pH, contact time and the concentration of thesolution, was optimized. The results indicated that Met-SBA-15and Cys-SBA-15exhibited good sensitivity and selectivity towards Hg2+. The adsorption equilibriumcould be reached within20min and the maximum adsorption capacity ofMet-SBA-15for Hg2+was88.7mg g-1at pH5.0and the maximum adsorptioncapacity of Cys-SBA-15for Hg2+was72.8mg g-1at pH2.1. However, His-SBA-15 had better selectivity towards Ni2+, and the maximum adsorption capacity ofMet-SBA-15for Ni2+was67.2mg g-1at pH3.1. Furthermore, the adsorption kineticswas also studied. The results showed that the pseudo-second-order equation was moresuitable for describing the kinetic adsorption process since the value of qe, calobtainedfrom the pseudo-second-order model was in more agreement with those got from theexperiment.