Adsorption of Heavy Metals and Organic Contaminants on Functionalized Periodic Mesoporous Organosilicates
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0930-JJ02-09
Adsorption of Heavy Metals and Organic Contaminants on Functionalized Periodic Mesoporous Organosilicates Fengling Ding, and Conrad Ingram Chemistry, Clark Atlanta University, 223 James P. Brawley Drive, Atlanta, GA, 30314 ABSTRACT Mesoporous organosilicates containing an ethylene bridge within the otherwise silicate pore walls and an additional organic functionality extended within the pore showed varying adsorption capacities for mercury and dimethylphenol. Thiol and imidazole functionalized organic-inorganic materials were effective for the adsorption of mercury, whereas the purely siliceous mesoporous MCM-41 was more effective for dimethylphenol adsorption than its organosilicate counterparts. INTRODUCTION Increasingly stringent water quality regulations continuously demand adsorbents of improved efficiency and high selectivity to remove organic and heavy metal contaminants. Ordered mesoporous organic and organic-inorganic hybrid materials offer significant potential as adsorbents to meet these demands due to their high surface areas, uniform, large, and tuneable pore sizes, and the ability to modify their surface chemistry to achieve high selectivity[1,]. These materials can potentially replace activated carbons which are costly to regenerate. While MCM41, the all-silica member of this mesoporous silicate family, is synthesized using a silica source only (e.g. tetraethylorthoslicate), organic functionalities can effectively be introduced as bridging components (e.g. -CH2CH2_) of the otherwise all silica pore-walls or attached to the walls through -O-Si linkage (e.g. (-O)3SiC3H7NH2) from the condensation of appropriate organosilicate precursors in the presence of a surfactant as the organic template. The surfactant can easily be removed by extraction or calcinations, to generate the desired pores[3]. This approach has generated a wide range of materials as potential adsorbents for organics and heavy metals removal from water[4,5] The objective of this research is to investigate the adsorption properties of mesoporous organic-inorganic hybrid materials for adsorption of heavy metals and organics. Materials were synthesized containing -Si– CH2CH2-Si- within the pore walls and (O)3SiC6H12X (X= SH, NH or imidazole) moieties anchored to the walls trough the -O-Si linkage with the organic species extended within the pores. The materials were evaluated in batch studies for the adsorption of dimethylphenol, representing phenolic compounds, and Hg22+ ion representing heavy metals. EXPERIMENTAL DETAILS Synthesis: Surfactant templated mesoporous organic-inorganic organosilicates were synthesized according to the methods of Burleigh et. al [5]. Reactants were combined in the following molar composition: 0.12 CTACl: 1-xBTSE: xR:1.0 NaOH:230 H2O, with x equal 0 for CB and 0.25 for samples CBIM, CBNH, CBSH. The respective organosilicate precursors were as follows: For CBIM-use (1,2-bis (trimethoxysilylethane ) BTSE; for CBSH use BTSE and (3-aminopropyltriethoxysilane ; for CBNH use BTSE and (3-aminopropyltriethox
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