Facile Synthesis of Thiol-functionalized Mesoporous Silica – Their Role for Heavy Metal Removal Efficiency

A simple approach based on the covalent grafting of 3-mercaptopropyltrimethoxysilane groups onto the framework of two types of mesoporous silica C16 (surface area: 1568.72 m2/g; pore size: 3.07 nm) using hexadecyltrimethyl ammoniumbromide and C9 (surface area: 779.83 m2/g; pore size: 4.51 nm) using nonyltrimethyl ammoniumbromide as templates has been reported. Various techniques were employed to confirm the thiol functionalization. A considerable decline in the surface area, pore volume, and interestingly an enhancement in the pore size were observed for functionalized materials. The functionalized derivatives were able to bind quantitatively several folds Ag+ and Hg2+ ions compared to that of unmodified mesoporous silica and a comparative study with earlier reports indicated that the mesoporous silica discussed in this present work showed superior adsorption behavior. Mercapto-functionalized mesoporous silica have not only exhibited an enhanced adsorption rate towards Ag+ and Hg2+ but also demonstrated that the maximum adsorption capacity of Ag+ (C16 = 0.73 mg/g; C16-SAn = 192.31 mg/g; C16-SH = 250.00 mg/g; C9 = 0.66 mg/g; C9-SAn = 181.82; C9-SH = 185.85 mg/g) and Hg2+ (C16 = 0.40 mg/g; C16-SAn = 114.94 mg/g; C16-SH = 126.58 mg/g; C9 = 0.31 mg/g; C9-SAn = 108.70; C9-SH = 112.36 mg/g) is hundred times higher than that of unmodified mesoporous silica. Thus, it is evident that these thiol-functionalized mesoporous silica can be promising adsorbents for the treatment of Hg2+ and Ag+ contaminants in aqueous solution.