Spray Drying Technology To Prepare Controlled Structure Of Catalyst And Its Performance Study

Advanced Oxidation Process (AOP) is an effective way to remove low concentration of pollutants in the water (10-2 ~ 10-3 M) . In this paper,we mainly carry out work on the catalyst used in photocatalytic oxidation and catalytic peroxidation .Photocatalysis is a comprehensive discipline relating to optics, electrochemistry, material science, surface chemistry and catalysis chemistry. The semiconductor photocatalyst are usually employed which can absorb the optical energy and produce the photo-induced holes and electrons which have strong oxidizability and reduction ability respectively. Thus the direct and indirect oxidation and reducing reaction can be occurred at the surface of the catalyst. What causes the great interest of the semiconductor photocatalysis in the scientific research area is the potential value to the problem of the energy utility and environmental purification. During past 30 years, photocatalysis has been extensively with great achievements. However, there still remain many problems to be solved. Efficient semiconductor photocatalyst need to be improved on the basis of fundamental research. As far as the general TiO2 photocatalyst, the broad band gap and low quantum efficiency confine its development. At the same time, besides TiO2 photocatalysts, it is also of great interest to find novel visible-light photocatalytic materials with narrow energy band gap and stable structure. In the past several decades, a variety of mixed metaloxides such as Bismuth titanates, bismuth ferrites bismuth tungstate had been extensively studied as a new class of photocatalysts. But the popular preparation method solid–solid reaction has the obvious shortcoming with low surface areas and difficult control of the microstructure, leading to the low catalytic efficiency.Because of its high efficient processing capabilities and cheapness, catalytic peroxidation technology has been widely used. The most common catalyst is Fenton reagent (Fe2+/H2O2). But the reagent only can be used in low pH range, can not be reused, and cause secondary environmental pollution in practical applications. Therefore, the development of heterogeneous catalysts which is highly efficient, stable, and easy to separate is the key technology. However, the research of heterogeneous manganese oxide catalyst is still difficult to further improve the catalytic activity. The relationship between structure and properties is not clear.The spray pyrolysis method which is time-saving, simple, and easy to control has been a popular method used to produce metal, metal oxides, and nano material. More over, the template method including soft templates and hard templates is also a effective method to control the pore structure of materials. Herein, we use spray pyrolysis method assisted with template method to prepare novel catalysts.Our work begins from the structure and morphology research of the catalyst to optimizing the preparation methods and conditions. The effect of crystal phase, texture and surface property to activity is explored to further develop practical catalysis technique. The detailed works are as follows:1. Novel Visible-Light Bi2Ti2O7 Photocatalysts Prepared by Spray Pyrolysis Assisted with SurfactantA novel microsphere of visible-light Bi2Ti2O7 (BTO) photocatalyst with porous structure is prepared by spray pyrolysis assisted with self-assembly of Pluronic F127 surfactant. The Bi2Ti2O7 photocatalyst obtained by using 3 g F127 surfactant and via being sprayed at 350℃followed by 500℃-calcination, shows the higher visible-light photocatalytic activity for both p-chlorophenol (4-CP) and rhodamine (RhB) aqueous solution, comparing with both P25 TiO2 and Bi2Ti2O7 catalyst prepared by the method of chemical solution deposition. According to the detailed characterizations, the excellent activity can be attributed to the high crystallinity of Bi2Ti2O7 without transformation to Bi4Ti3O12 crystal phase, the high surface area via the formation of stable porous structure, which is favorable to the adsorption of pollutant molecules and light utilization, and the promoted light adsorption in visible region due to the narrow band gap of 2.9 eV.2. Novel hollow sphere Visible-Light BiFeO3 Photocatalysts Prepared by Spray PyrolysisA novel visible-light BiFeO3 (BFO) photocatalyst is prepared by spray pyrolysis. Comparing to the traditional method, the facile spray pyrolysis process can produce BiFeO3 with hollow structure. During photodegradation of RhB under visible light irradiation, the BFO sample exhibits much higher activity than P25 TiO2. By changing the amount of glycerol, sample with different thickness can be obtained. The effect of crystallinity on catalytic efficiency is also discussed.3. Core-Shell Microspherical Mn2O3 Directly from Spray PyrolysisA novel core-shell Microspherical Mn2O3 is obtained by an spray pyrolysis method assisted with glucose. Compared with previous methods, our preparation is very fast. The characterizations reveals core-shell spherical structures of the sample. The catalytic peroxidizing activities of degradation of methylthionine chloride (MB) in aqueous solution is evaluated. It was found that the core-shell Mn2O3 exhibit higher activity than the commecial Mn2O3.