Studies On Synthesis Of Mesoporous TiO₂ By Microwave Assisted Sol Gel Method And Its Catalytic Activity

With the development of economy and science and technology, the protection of the ecological environment has become one of the most concerned topics. As a new field of environmental pollution treatment, semiconductor photocatalysis is potential to degrade organic pollutants efficiently. Mesoporous TiO₂ is widely used in the field of environmental pollution treatment because of abundant sources, low price, no toxicity, good chemical stability and so on.Mesoporous TiO₂ has the characteristics of high specific surface area,excellent adsorption performance and an ordered pore structure which is easy to react to. However, due to the great band gap of TiO₂, must under the conditions of high energy ultraviolet radiation to the excitation of electrons into the conduction band and the photogenarated e--h+ pairs can be easy to recombination, which make pure mesoporous TiO₂ have low catalytic activity. This paper mainly studied the synthesis of doped mesoporous TiO₂, by doping F, Co elementst to increase specific surface area of photocatalysts, reduce the band gap of TiO₂, improve photons utilization rate of catalyst, and ultimately improve the photocatalytic activity of the catalyst.?1?Synthesis of photocatalysts by microwave assisted sol-gel method. Synthesis of different F, Co doped F-MT and Co-MT, as well as F, Co co doped F-Co-MT by microwave assisted in a relatively shorter time. The structure, properties and morphology of photocatalysts were characterized by FT-IR, XRD, N₂ adsorption desorption, SEM, and so on. The results showed that the mesoporous TiO₂ was anatase TiO₂, the optimum calcination temperature was 400?, when Doping amount of F and Co were 2% and 5%, it was favorable to form anatase, and the size of TiO₂ crystal are proper. N₂ adsorption desorption results show that the specific surface area of MT, 2%F-MT, and 2%F-5%Co-MT were 70.706m2/g, 143.375m2/g, 114.613m2/g, respectively, which showed that the doping of F significantly enhanced the specific surface area of mesoporous TiO₂. In addition, the SEM results showed that the prepared MT, 2%F-MT, 2%F-5%Co-MT are mesoporous microspheres, and the morphology of 5%Co-MT is a worm-like. The surface of 2%F-MT microspheres was fluffy, and the particles were uniform, well dispersed.?2?Determined the photocatalytic degradation performance and mechanism of prepared doped mesoporous TiO₂ under visible light with the methyl orange solution as model pollutant. When the initial concentration of MO is 15mg/L, amount of catalyst is 0.16 g and photocatalytic degradation 2h under visible light, the photocatalytic degradation rate of 2%F-MT, 5%Co-MT and 2%F-5%Co-MT reach to 99.07%, 88.05% and 91.34%, respectively. The results show that, after modification, the mesoporous TiO₂ photocatalytic activity improved markedly, and the catalytic activity of the synthetic 2%F-MT is the highest. The reuse and the photocatalytic degradation mechanism of 2%F-MT were explored, and the results showed that 2%F-MT had better repetitive use stability. The photocatalytic degradation mechanism of the 2%F-MT was inferred by free radical trapping experiments, and proved that ?O₂- is an important substance in photocatalytic degradation process.