| 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. Whether the sewage can reach the emission standard is determined by the contaminative index of the sewage, among which the most important is the COD value of the sewage. COD is defined as the amount of oxygen equivalents consumed in the oxidation of organic compounds by strong oxidizing agents such as dichromate or permanganate and is expressed by quantity (mg l-1) of oxygen. The accuracy is determined by the oxidizing extent of the organic compounds or other reductive substances. 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 amperometry or 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 method.This dissertation fell into three hierarchical levels and ten sections. Firstly, on the basis of the preparation of many kinds of nano-semiconductor oxides, how to improve the electrocatalytic or photocatalytic property of the nano-semiconductor oxides and how to optimize the best path of the oxidation of the organic compounds were discussed. Then the existence of HO-, the active substance, was detected in the catalyticai and oxidizing system of the nano-semiconductor by CZE-AD, ESR, etc, which provided a useful analytical and detective method for the detection ofthe HO- and display the oxidizing mechanism of the nano-semiconductor. Lastly, the optimal technological conditions of the detection of the COD by making use of nano- semiconductor as the catalyst in the electrocatalytic or photocatalytic reaction was discussed and its basic theory, on which some detective equipments such as "fast on-line COD electrochemical detector" and "fast COD photoanalytic instrument" were developed. These works combined the nano-science with analytical chemistry and provided an effective method for further researching the oxidizing and catalytic mechanism of the nanomaterials, their application in the analytical chemistry and the development of the products, which had a deep meaning in the nanotechnology, analytical chemistry, environmental chemistry, environmental detection and the development of the analytical instruments.(1) Critical ReviewsIn this part, four parts, that is, the development of the nanomaterial, the preparation 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.(2) Preparation and characterization of nano-PbOz modified electrodeOf late, there is a great interest in the improvement of lead dioxide as an anode material owing to its high electrical conductivity, large oxygen overpotential and chemical inertness. PbO2 can be obtained as anodic deposits from solutions of the low-valence ions. Its electrocatalytic activity depends upon its structure, morphology and phase composition, which are highly relied on deposition methods. In this chapter, a lead dioxide film modified electrode was prepared at platinum substrate and its deposition conditions and formation mechanism were studied. The effect of F", Ce3... |
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