| In recent years, organic-inorganic hybrid mesoporous silica-based materials with high surface area, large pore volume and adjustable pore size have attracted much attention across the world, because they are promising in catalyst, adsorption, controlled dilevery, energy storage and conversation, chemical sensors, etc. The research on the synthesis and application of mesoporous silica-based functional materials is one of the focuses in chemistry, materials science, physics and life science. With the growing requirement for natural resources, more emphasis is laid on sustainable development and environmental protection. Therefore, the recovery and reuse of metals in wastewaters is advantagous to make full use of metal resources and eliminate pollution. Adsorption technique is regarded as an effective and environmental benign route for metal recovery. So adsorbents with excellent separation performance are the aim of many research activities. The work described in this dissertation is focused on the synthesis and characterization of organic-inorganic hybrid silica materials and surface modification of the ordered mesoporous silica. The adsorption properties of the synthesized materials for metal ions, especially for precious metal ions are investigated.Periodic mesoporous organosilicas (PMOs) with different content of 1, 4-diureylenebenzene functional group (0-15%) immobilized in the silica framework were synthesized under both acid and base conditions, with EO20PO70EO20 (P123) and cetyltrimethylammonium bromide (CTAB) as templates, respectively. It is found that the PMOs prepared under acid condition possess two-dimensional hexagonal cylindrical mesoporous structure. The hydrogen-bond interaction was detected between the ureylene groups in the silica wall and the interaction becomes stronger with the increasing content of the ureylene group. PMO0.2exhibits uniform "rod-like" morphorlogy. The PMOs synthesized in basic solution exhibit high surface area and "worm-like" hierarchical mesoporous structure. PMOs demonstrate good adsorption performance for Au(Ⅲ) in acidic solutions. Moreover, the "worm-like" hierarchical mesoporous structure make more organic groups empose to pore surface, which is ready to be accessed by Au(Ⅲ). Therefore, the PMOs synthesized under basic condition have larger adsorption capacity and faster adsorption rate. The Au(Ⅲ) can be reduced to metallic gold and aggregate to large particles on the surface during the interaction with 1,4-diureylenebenzene groups anchored in the silica wall. Pyrazole-SMS has been synthesized by grafting pyrazole moeties on the pore surface of mesoporous silica with spherical morphology of 4 - 6μm through "homogeneous post-grafting" method. Pyrazole-SMS show good adsorption ability for AuCl4-, PdCl42-and PtCl62- in acidic solutions and the maximum adsorption capacity are 89.4mg/g, 40.0mg/g and 44.7mg/g, respectively. The meso-structure of pyrazole-SMS facilitates the transportation of the precious metal ions in it and the adsorption equilibrium is attained in 20 minutes.NH2-SBA-15, Imi-SBA-15 and Tri-SBA-15 have been prepared by functionalization of SBA-15 with aminepropyl, imidazole and 1, 2, 4-triazole through one-step or two-step post-grafting method. Different organic groups make the modified mesoporous adsorbents have zero potential at different pH values. NH2-SBA-15, Imi-SBA-15 and Tri-SBA-15 demonstrate good adsorption performance for Cr(Ⅵ). The maximum adsorption capacity of NH2-SBA-15 for Cr(Ⅵ) reaches 405mg/g. It is found that the electronic interaction between Cr(Ⅵ) species and the pendent functional groups play a key role in the adsorption process. The adsorption capacity increases with the growing content of the grafted organic groups. However, steric hindrance of the heterocyclic groups will slow down the adsorption rate.
|
PDF Full Text Request