| The civilian, commercial, and defense sectors of most advanced industrialized nations are faced with a tremendous set of environmental problems related to the remediation of hazardous wastes, contaminated groundwaters, and the control of toxic air contaminants. Over the last 10 years, problems related to hazardous waste remediation have emerged as a high national and international priority. In order to address this significant problem, extensive research is underway to develop advanced analytical, biochemical, and physicochemical methods for the characterization and elimination of hazardous chemical compounds from air, soil, and water.Semiconductor photocatalysis is intended to be both supplementary and complementary to some of the more conventional approaches to the destruction or transformation of hazardous chemical wastes. Over the last 10 years, the scientific and engineering interest in the application of semiconductor photocatalysis has grown exponentially. Up to now, semiconductor photocatalysis has been applied to a variety of problems of environmental interest in addition to water and air purification. It has also been shown to be useful for the destruction of microorganisms such as bacteria and viruses, for the inactivation of cancer cells, for odor control, for the photosplitting of water to produce hydrogen gas, for the fixation of nitrogen, and for the cleaning up of oil spills. The emphasis of this paper lied in the mechanical research and application of photocatalysis, and the whole paper can be classified into the following five parts:Part 1 Overview (Chapter 1)In Chapter 1, we attempt to give an overview of some of the underlying principles governing semiconductor photocatalysis and to review the current literature in terms of its potential applications as an environmental control technology and analyzing tool.l'art 2 Preparation and Characterization of Film and Powder of Nanostructured TiO2. (Chapter 2)In Chapter 2, transparent TiO2 films were prepared by two means, sol-gel and cathodic electrodeposition method, respectively. The experimental results achieved byAtomic Force Microscopy (AFM) and X-Ray Diffraction Analyzer (XRD) showed that the films were mainly composed of anatase TO2, and the size of the particles of TiO2 lied in the scope of nanometers. The products by these two means were prominent for their photoelectric response and electric conductivity. But the low load of nanometer materials rendered insufficient photocatalytic capacity, and limited their application in wastewater treatment. To improve its exhibition in environmental optimization, TiO2 powder was produced by thermal hydrolysis of TiO2 and used as the photocatalyst for wastewater treatment after being adhered to sphere molecular sieves.Part 3 Mechanical Study of Semiconductor Photocatalysis (Chapter 3 ~ 5)In this part, three different means were adopted to study the mechanisms of the semiconductor photocatalysis, focusing on the study of oxidative intermediates and the band gap between the valence and conductive band of semiconductor.In Chapter 3, high performance liquid chromatography coupled with electrochemical detection (HPLC-ED) was used to determine the quantum yields of hydroxyl radicals during the photocatalysis. And the results showed that the photocatalytic process could not be interpreted by hydroxyl radicals alone, but its cooperation with photoinduced holes together.For it's very hard to distinguish the roles of hydroxyl radicals and photoinduced holes in the photocatalysis. A new definition of Total Oxidative Intermediates (TOI) was introduced in Chapter 4. TOI included the quantity of hydroxyl radicals and the photoinduced holes, which reacted directly with the organics presented in the photocatalytic system. The quantum yields of the TOI were determined by photocurrent measurement. Compared with Chapter 3, TOI interpreted the photocatalytic process more successfully.In Chapter 5, TiO2 film was prepared and the current signals produced on the film were recorded during illumination with ligh...
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