Synthesis Of Novel Inorganic Aerogels For Adsorption/Photocatalytic Performance Application

Currently, the issue of environmental pollution has been increasingly prominent. The treatment of waste water especially the treatment of organic pollution has become hot issue with the grave pollution of water resource. As one of the novel environmental restoration, adsorption/photocatalysis gains more and more attention in the field of treatment of waste water. As well known, inorganic aerogels are lightweight, nano-porous materials with lots of surface area and good adsorption properties. However, there are still many problems in the application process, such as, long preparation period, energy-extensive consumption and reclamation difficulty. Thus, preparation of novel inorganic aerogels to build efficient adsorption/photodegradation system is significant theoretically and practically.In order to realize high-level utilization of inorganic aerogels, this dissertation presents a systematic study of novel inorganic aerogels for adsorption/photocatalytic performance application:different groups on surface of silica aerogels, copper based microspheres, rutile titania aerogels, titania-containing silica aerogels and novel photocatalysts grown from silica aerogels precursors were prepared by ambient pressure drying and surface modification technology, catalytic carrier refactoring technology and adsorption/photocatalytic coupling technology, respectively. By combining variety of systemic characterization, the crystalline phase, microstructure, apparent groups, specific surface area and pore structure of novel inorganic aerogels were also investigated. Meanwhile, the main goals were (1) to investigate the formation mechanism of inorganic aerogels;(2) to clarify the mechanism of novel adsorption/photocatalytic aerogels to remove organic pollution from aqueous solution;(3) and to investigate the potential applications of the novel inorganic aerogels’ unique properties.The research details of the dissertation are as follows:1. Synthesis of different groups on the surface of silica aerogel by ambient drying process and their adsorption capacity of dyes (1) Hydrophilic and hydrophobic silica aerogels were prepared by sol-gel process with ambient drying process. These novel silica aerogels were also used for adsorption of cationic dye (Rhodamine B and Methylene blue). Meanwhile, the hydrophilic silica aerogels were prepared by using sol-gel method, ambient drying process and calcinations with trimethylchlorosilane as modifier reagent. This hydrophilic silica aerogels were used for adsorption of different dyes (Rhodamine B, Methylene blue, Crystal violet and Orange Ⅱ). Results showed that this kind of silica aerogels have good adsorption effect of cationic dye Rhodamine B, the adsorption capacity of more than100mg/g.(2) Adsorption experiments of different groups on the surface of silica aerogels were used to study pH value, adsorption time and initial concentration and other factors. Using Langmuir and Freundlich isothermal models examine the adsorption equilibrium properties of these novel silica aerogels. Comparisons of these novel silica aerogels’dyes adsorption prove that silica aerogel has excellent dyes adsorption and the adsorption processes of aerogels were influenced by various factors (hydrogen bonding, hydrophilic/hydrophobic and electrostatic interactions, etc.).2. Preparation of novel non-silica aerogels by epoxide additional method and their application in dyes wastewater treatment(1) The hierarchical of Cu2Cl(OH)3microspheres were synthesized by sol-gel process and freeze drying. The size and surface area of the microspheres are ca.1-2μm and76.61m2g-1, respectively. Methylene blue was chosen to investigate the adsorption capacity of the as-prepared adsorbent. The effects of various experimental parameters, such as pH, initial dye concentration, and contact time were investigated. Adsorption data was modeled using the Freundlich adsorption isotherm. The thermodynamic analysis presented the exothermic, spontaneous and more ordered arrangement process.(2) The hydrophobic rutile-titania aerogels were successfully prepared by non-alkoxide ambient pressure drying through a modification process. The crystalline phases, microstructure, specific surface area and structure of materials were characterized by various methods. The experimental results demonstrated that the as-prepared samples nanoparticles with rutile crystalline structure were uniformly distributed. The UV-resistant hydrophobic samples having high surface area were used as photocatalysts for dye degradation reaction. Experimental results showed that ultraviolet resistance hydrophobic rutile-titania aerogels can maintain good contact angle with water after180min illumination.3. Preparation of novel photocatalysts using silica aerogels as substrate and their catalytic performance(1) The developing of a novel and facile way to synthesize composite aerogels plays an important role in the applications of aerogels. UV-resistant hydrophobic titania-containing silica aerogels are prepared for the first time using potassium titanate as precursor by a modified ambient pressure drying method. The well established silica-titania networks, which can be tuned from10nm to30nm by adjusting the precursor content in preparation process, provides effective confinement of spherical solid clusters. The UV-resistant hydrophobic composite aerogels show excellent photocatalytic dye degradation activity under visible light irradiation. This can be ascribed to the insert a suitable titania into the silica organizational structure.(2) Bismuth silicate with two morphologies (nanoflowers/nanoplates) was successfully fabricated with silica aerogels via a hydrothermal method in Polyvinylpyrrolidone-mediated processes for the first time. It was found that the concentration of PVP plays an important role in the formation of the hierarchical nanoflowers. The formation mechanism for this novel morphology was proposed on the basis of experimental results. Moreover, the photocatalytic performances of Bi2SiO5nanoflowers/nanoplates were also investigated. The results revealed that Bi2SiO5nanoflowers exhibited higher activity than Bi2SiO5nanoplates due to its suitable morphology, higher BET surface area.