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Study On The Synthesis Of Titanium Dioxide Photocatalyst And Its Photocatalytic Activity To Organophosphorous Pesticides

Posted on:2005-01-23Degree:MasterType:Thesis
Country:ChinaCandidate:B ZhouFull Text:PDF
GTID:2121360125450846Subject:Analytical Chemistry
Abstract/Summary:PDF Full Text Request
It has been deeply studied on the treatment of organic pollutants in pesticide wastewater by semiconductor photocatalytic degradation. Titanium dioxide has become an important and developing photocatalyst for its higher stability and activity, cheapness, intoxicity, difficult to dissolve in the acid and alkali conditions. The pollutants can be entirely broken down to innoxious matters by photocatalytic degradation which can be finished at normal temperature and pressure in short times, so photocatalysis method has become one of the most effective method to degrade vary kinds of polluters. However, usual suspension photocatalysis oxidation had some disadvantages, such as photocatalyst was apt to inactivate and agglomerate, difficult to reuse and easy to cause the second pollution. These shortcomings limited the development of titanium dioxide. So researchers focused the emphasis on the synthesis of the immobilized photocatalyst that could enhance its photocatalytic activity. This paper prepared titanium dioxide photocatalyst supported on a natural zeolite with tetrabutyl titanate as titanium source. The chemical combination was achieved between titanium dioxide and the mineral. The anatase had the best crystal at calcinating temperature of 200℃ which had a bigger specific surface area and photocatalytic activity. At the same time, it was easy to reuse and could not cause the second pollution. The mineral and the anatase achieved good combination, which overcome the disadvantages of titanium dioxide. As a result, the composite titanium dioxide had better using foreground than the suspension one. The titanium dioxide sol was synthesized by acid-catalyzed sol-gel method and then the TiO2/zeolite photocatalyst with which supported on natural zeolite was obtained. The chemical combination was achieved between titanium dioxide and the mineral that has a bigger specific surface area. The experimental results showed that titanium dioxide supported on a natural zeolite treated at 200℃ had the best photocatalytic activity. Structure test showed it was anatase that had the best crystallization and the biggest content at 200℃. The synthesized titanium dioxide transformed from anatase to rutile gradually with the calcinating temperature increased. The electron and hole produce easier for anatase than that of rutile, so it has a high photocatalytic activity.The organophosphorous pesticides were photocatalytic degraded by the synthesized titanium dioxide. Dichlorvos can be entirely decomposed with general conditions in irradiation for 150min and it was the easiest one, Phorate was the easier one, and Parathion was the most difficult one to break down, which had relation with their molecular structure. The COD removal rate were all about 90 percent when they had been entirely degraded. Since the natural zeolite had better absorption, dichlorvos had 10 percent degradation when the blank experiment was carried out by the zeolite only. At the same time, the parallel experiment was done and there was no degradation. That is to say, the vision light had no contribution to the photodegradation. During the course, the odor of the Phorate disappeared which showed the photocatalytic method could remove the odor. The influence factors such as the initial pH, the additional hydrogen peroxide, the content of titanium dioxide and some additional inorganic anion on photocatalysis degradation with dichlorvos as aim contaminants were further studied. The results showed that dichlorvos could be easily decomposed at strong alkaline conditions and could be broken down at pH2.0. There was no obvious difference in the degradation rate at the initial pH of 4.0, 6.0 and 9.0, and the final pH of reaction solutions were around 6.0 in the study. The problem in using titanium dioxide as a photocatalyst is recombination of electron and hole. One strategy for inhibiting theirs recombination is to add other electron accepters to the reaction. It can reduce the electron/hole recombination and then produce more ·OH on the surface of t...
Keywords/Search Tags:Titanium Dioxide, Natural Zeolite, Photocatalytic Degradation, Organophosphorus Pesticides, dichlorvos, Supported Photocatalyst
PDF Full Text Request
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