Hydrothermal Synthesis Of Bi < Sub > 2 < / Sub > Send < Sub > 6 < / Sub > And Its Photocatalytic Performance

Nano photocatalytic materials as a catalyst can catalytic degradation thousands of toxic compounds. It is mild, non-toxic, no secondary pollution in the photocatalytic reaction, and is an environmental protection material with very development prospect. Moreover, solar energy is inexhaustible energy, so using the solar energy photocatalytic degradation of organic pollutants has important significance to solve environmental problems, and researching visible light catalyst is the key to realize the efficient utilization of the sunlight.In recent years, the Bi2WO6catalyst proved favourable photocatalytic activity in visible light, so researching preparation and visible photocatalytic performance of Bi2WO6widely cause the attention of people. Research shows that, via changing the synthesis conditions can control the morphology of Bi2WO6and then improve its light catalytic properties. However, how to targeted to improve the light quantum efficiency of the catalytic reaction, reveal the structure-activity relationship of Bi2WO6, thus further guide controllable synthesis efficient catalyst to photocatalytic degradation of pollutants, which is still the research hot spot and the challenge in this field.This thesis mainly studied the influence of different preparation conditions on the structure and properties of Bi2WO6photocatalyst. The structure and properties of the catalyst were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible diffuse reflective spectrum (UV-Vis diffuse), and N2isothermal adsorption-desorption technology. The catalytic performance in visible light catalytic degradation of dye methyl orange and the dynamic behaviors of Bi2WO6were studied and the effects of structure and properties of the catalyst on its photocatalytic performance were discussed.First of all, effects of the different preparation methods (hydrothermal synthesis, precipitation, citric acid method) and preparation conditions on the structure, properties and visible photocatalytic degradation of methyl orange performance of as-prepared Bi2WO6catalyst were studied. Research found that the Bi2WO6catalyst prepared by hydrothermal synthesis method showed highest performance on photocatalytic degradation of methyl orange. That was in the catalyst dosage of1g/L,100mL concentration of10mg/L of methyl orange solution, visible light irradiation4h of the reaction conditions, the degradation rate of the methyl orange can reached70.3%. The corresponding optimization hydrothermal synthesis conditions of the catalyst were:Bi(NO3)3·5H2O and (NH4)H5[H29WO4)6]·H2O as inorganic raw materials (mixed solution pH=7), the triblock copolymer F-127as a surfactant, and200℃hydrothermal treatment24hours.Secondly, the Bi2WO6catalyst prepared at the optimization hydrothermal synthesis conditions as research object, effects of the preparation system pH value (pH=2,5,7and10) on morphology and semiconductor band gap energy of catalyst and the performance on visible photocatalytic degradation of methyl orange were investigated. The results showed that the preparation system pH value significantly affect the morphology and semiconductor band gap energy of the catalyst. Scanning electron microscopy results can see:when the preparation system pH value was2and10, the as-prepared Bi2WO6looked like short strip; while it was observed that Bi2WO6mainly appeared thin slice at the preparation system pH value of5and7. UV-Vis diffuse results showed that the band gap energy of the as-prepared Bi2WO6semiconductor increased with increasing the preparation system pH value, visible absorption performance was the best in preparation system pH=2. In addition, preparation system pH value closely related with the performance of catalyst photocatalytic degradation of methyl orange. The Bi2WO6catalyst prepared at preparation system pH=2showed highest photocatalytic performance, which was attributable to its most narrow semiconductor band gap energy in the visible range and the largest specific surface area.Finally, the law of effects of reaction conditions:catalyst dosage, reaction time, methyl orange solution initial concentration, pH value of methyl orange solution on the catalytic activity were investigated. The results showed that the reaction accorded with pseudo-first-order reaction dynamic law and the reaction rate constant increased with reducing the preparation system pH value.