| Advanced Oxidation Technology(AOT) is a new wastewater treatment technology. It has lots of virtues such as efficiency, high oxidation rate, non-pollution and so on. Many poisonous and bio-recalcitrant organic compounds can be decomposed efficiently by AOT. Furthermore, combination of two or more technologies expectedly enhances the effects of degradation. In recent years, much attention has been paid to AOT in wastewater treatment field. Pentachlorophenol is a recalcitrant compound. It is carcinogenic and toxic to plants, animals, and human even at low concentration. PCP is on the US Environmental Protection Agency list of Priority Pollutants. In this thesis, heterogeneous photocatalytic technology and ozonation combines with photocatalysis are introduced for the degradation of PCP.(1) In suspended system, photocatalytic oxidation for PCP by using TiO2 is studied. The rules of photocatalysis of PCP as well as the influential factors for the degradation of PCP are discussed and examined, respectively. The results show that in dark reaction, PCP is not adsorbed. The degradation efficiency with photocatalysis arrives to 65％and is higher than that with direct photolysis, which only reaches 15％after 200 minutes. The optimum dosage of catalyst is 0.8g/L. Moreover, the increase of both reaction time and light intensity improve the degradation ratio of PCP. The effect of UV strength is obvious and the degradation ratio of PCP arrives at 93.3％.(2) TiO2 photocatalysts doped with iron are prepared by sol-gel method and wet impregnation way. Some influential factors on the photocatalytic performance including preparation technique, iron content, calcination temperature of sol-gel method have been investigated. It finds that iron doped TiO2 prepared by sol-gel method shows a better catalytic behaviour than that of bare TiO2, when the catalyst with iron content of 0.05％(molar ratio) is calcined at 500℃. The photoactivity is related to the structure of TiO2 and the anatase phase plays a beneficial role in activity. The activity of impregnated TiO2 is reduced with increasing iron content. In conclusion, the photoactivity of TiO2 is not improved obviously by iron dopant.(3) Pentachlorophenol is degraded by using ozonation and photocatalysis in the presence of analytic-grade TiO2. The degradation of pentachlorophenol by UV, O3, UV/TiO2, O3/TiO2/UV processes has been studied. The effects of ozone flow rate, ozone output, concentration of pentachlorophenol, initial pH value and carbonate in the O3/TiO2/UV process are examined, respectively. The results show that the degradation ratio of PCP in the process of O3/TiO2/UV comes to 86.2％, which is more efficient than those of other three processes. The degradation ratio increases with the increasing flow rate of ozone and output of ozone. After 30 minutes, the degradation efficiency of PCP is over 98.4％when ozone output is at 54.5 mg/h. To decrease the initial concentration of PCP tends to enhance the degradation ratio remarkably while the effect of initial pH value is not evident. The existence of carbonate significantly reduces the degradation ratio of PCP. In the process of O3/TiO2/UV, the generation of OH radicals plays a significant role in the degradation of PCP in addition to the direct ozonation of PCP. |
