| With the increasingly severe environmental pollution, the department of environmental protection is attaching greater importance on the environmental detection. The advance of the detective equipment is the indication of the modern detection. The water pollution is a large aspect of the environmental pollution,so water environment determination are paid attention to all over the world. Defined as the number of oxygen equivalents consumed in the oxidation of organic compounds by strong oxidizing agents, chemical oxygen demand (COD) has preferentially been used as a parameter to represent the degree of organic pollution of waste water. With its special photoelectrical characteristic, nano-semiconductor oxide can produce strong oxidizing agents which include oxygenic radicals, such as HO-, through which the pollutant in the aqueous system will experience electrocatalytic or photocatalytic process and then be reduced into water and carbon dioxide. On the basis of this theory, the fast oxidation of the organic pollutants and the measure of the quantity of the organic compounds in the aqueous system through photometry can be achieved, which will bring about the fast and on-line detection of the organic pollutants and provide a brand new concept and methodThe photocatalytic mechanism of nano semiconductor is studied. A method for the determination of COD using a system containing nano metal oxides and inorganic oxides is described. The operation conditions are optimized. Also one kind of COD analytic instrument based on colorimetric detection method is developed.These methods and instruments have good behaviors such as high sensitivity, a high linearrange, a short analysis time and simple operation. The results are well correlated with the COD value obtained using conventional methods . They can offer a great potential of applications to on-site monitoring of COD.The first chapterIn this part, four parts, that is, the development of the nano-semiconductor oxides and their application and development in the environmental analysis.the oxidizing and catalytic mechanism of the nano-semiconductor and the research on the measurement of the oxygen containing radicals and the current circumstances of the development of the fast COD detector in the waste water system were discussed and a detail outline and review of the development in the current area was introduced.The second chapterThe photocatalytic reduction of Cr( VI) in TiO2-organics co-existed system was studied. The effect of various initial concentration of Cr( VI), varous PH values, TiO2 adding, temperature, co-existed organics on photoredution of Cr (VI) have been investigated. The characteristics of photocatalytic reduction of Cr(VI) were verified, the reaction apparently proceeded according to the first-order kinetics. The acidic solutions were favorable for the photoreduction of Cr(VI). In the low light intensity, increasing the temperature would increase the reduction rate of Cr(VI ), but was ultimately influenced by the amount of TiO2 present in solutions. The pesence of glucose might act as scavenger for holes and promoted the photocatalytic reduction of Cr(VI) The third chapterA photocatalytic method for the determination of chemical oxygen demand (COD) using a nano-TiO2-K2Cr2O7 system is described. The measuring principle is based on direct determination of the change of Cr(III) concentration resulting from photocatalytic oxidation of organic compounds and simultaneous photocatalytic reduction of stoichiometrically involved K2Cr2O7 in the solution. The operation conditions were optimized. The determinative COD value using this method wascalculated from the absorbance of Cr(III). The operational characteristics of this method were demonstrated by use of a standard glucose solution as substrate. This method was also applied to the determination of the COD of wastewater samples. The results were in good agreement with those from the conventional (i.e., dichromate) COD methods.The fourth chapterA new photocatalytic oxidation method using nano Z...
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