Functionalized mesoporous SBA-15 silica molecular sieves with mercaptopropyl groups: Preparation, characterization and application as adsorbents

Mesoporous SBA-15 silica molecular sieve has been synthesized, and functionalized with mercaptopropyl groups via incipient-wetness impregnation of (3-mereaptopropyl)-trimethoxysilane. A thorough characterization revealed that the channels of the SBA-15 silica is uniformly lined with mercaptopropyl groups up to a maximum molar percentage loading of ca. 14.8 % with respect to the parent SBA-15 silica while retaining the original mesoporosity. The incorporated mercaptopropyl silane groups are chemically bonded to surface silicons associated with the silanol groups of the parent SBA-15 silica and remain intact during various stages of the preparation. The functionalized mesoporous SBA-15 silica materials are hydrophobic, and perform well as adsorbents in removing trace amounts of mercury and cadmium in various gas streams. Adsorption capacity for mercury vapor increases eight-fold from parent SBA-15 silica to the material with 1% molar percentage loading of mereaptopropyl groups, then declines with further increase in the loading of the mercaptopropyl groups. This suggests that the isolated mercaptopropyl groups serve as preferred adsorption sites for mercury vapor.