| Photocatalytic oxidation technology is an extremely attractive method for water deep treatment, which is of high efficiency, energy saving and non-second contamination and provides a promising strategy for disposing organic dye wastewater.Recently, with continuously being investigated the method of photocatalytic oxidation using semiconductors , layered niobates have been attracted extensive attention. Layered niobates with a layered structure have interesting chemical properties in such fields as intercalation, ion-exchange, potocatalysis, electrochemical activity, and their properties change substantially with various kinds of molecules or ions existing in the interlayer. Comparing with other layered niobates, potassium triniobate (KNb3O8) was mainly investigated of its luminescence property, however, was not involved in its photocatalytic property.In this thesis, three methods were studied on improving the efficiency of photodegradation.-(1) KNb3O8 was prepared by solid-state reaction method through the heating of a stoichiometic mixture of Nb2O5 and K2CO3. Scanning electron microscope (SEM) and X-ray diffractometer (XRD) were used to characterize the structure of the photocatalyst. The results of XRD and SEM showed that the prepared sample consisted of a nearly single phase of layered KNb3O8 when it was calcined at 900℃ for 2h, and KNb3O8 particles was with diameters of 1 -2μm.(2) Acid red G was selected to simulate organic dye wastewater which was treated by photocatalytic oxidation using the KNb3O8 as photocatalyst. Affect factors, such as catalyst dosage, initial concentration of acid red G solution, etc, and the kinetics of photocatalytic oxidation reaction were studied. In addition, Through the analysis of UV-VIS spectrophotometer, the mechanism of acid red G degradation was discussed. Experiments indicated KNb3O8 photocatalyst showed high photocatalystic activity to photodegrade acid red G under UV irradiation, which was prepared at 900 ℃ for 2 h.When the concentration of acid red G solution was30mg/L, the degradation rate was 97% after 2 h. Degradation rate of 50mg/l acid red G could also reach 87.03%; The photocatalytic activity was in inverse proportion to initial concentration of solution. The results of the kinetics research showed that the reaction was first-order and was coincident with Langmuir-Hinsheluwood(L-H) equation; UV-VIS absorption spectra record illustrated that though it could be decomposed under UV light by itself a little, the decolouration of acid red G was due to the degradation by KNb3O8, but not to the adsorption on it.(3)The preliminary research of modification photocatalyst was found that doping low concentration copper can significantly enhance the photocatalytic activity of KM^Os. The kinetics and mechanisms of photocatalytic oxidation reaction for acid red G were studied. The results of XRD and SEM showed that low concentration copper dopant didn't change the structure of KNbsOs; Experiments indicated that the optimum Cu dopant concentration of the catalyst was 0.3 wt. %, and its degradation rate was 98.21 %. But doping with high concentration of Cu would decrease the photocatalytic activity, and when doping with 5wt. % Cu, the degradation rate was only 9.15 %; The results of the kinetics research showed that the photocatalytic reaction of acid red G by low concentration Cu-doped KM^Os was first-order.
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