Synthesis and characterization of cubic thiol-functionalized periodic mesoporous organosilicas as effective mercury ion adsorbents

Well-ordered thiol-functionalized periodic mesoporous organosilicas (SH-PMO) with ethane bridging groups and cubic Pm3n symmetry for aqueous mercury removal have been synthesized via co-condensation of tetramethoxysilane (TMOS) with 1,2-bis(trimethoxysilyl)ethane (BTME) and 3-mercaptopropyl-trimethoxysilane (MPTMS) in a highly acidic medium by using cetyltriethylammonium bromide (CTEABr) as the template. The SH-PMO materials thus obtained have been characterized by X-ray diffraction, nitrogen physical sorption, thermogravimetric analysis, and solid-state Si-29 and C-13 NMR spectroscopy. We have found that it is necessary to employ a controlled amount of BTME in order to preserve the cubic mesoporous structure in the resulting material when a high quantity of mercaptopropyl groups is incorporated. Direct evidence of the presence of chemically attached thiol and ethane moieties is provided by Si-29 and C-13 magic angle spinning (MAS) NMR spectroscopy. The maximum content of the attached thiol group(-SH) in the mesoporous framework is 2.40 mmol/g. The total access of the Hg2+ ions to every complexation site, i.e., an Hg/S ratio close to 1, in the SH-PMO materials is also demonstrated, and a maximum mercury loading capacity of 464 mg/g is achieved. This makes its effectiveness for mercury ion trapping comparable to that of the highest capacity materials previously reported. C-13 cross-polarization magic angle spinning (CPMAS) NMR demonstrates that the C-13 chemical shift of the carbon atom adjacent to the -SH group is highly sensitive to the Hg2+ ion binding. (C) 2008 Elsevier Inc. All rights reserved.