Research On The Key Factors Of Dye Degradation With Microwave Assisted Photochemical Method

Recently, considerable attention has been focused on the application of photocatalytic oxidation of industrial wastewater because of high efficiency and low cost. Researchers are interested in optimization of photochemical reactor, modication of catalyst and combination of photochemical method with other technologies. However, the efficiency of light source, temperature and oxidant are investigated in a self-assembly reactor. The main parts of the thesis include:(1) Oxidative characteristics of new electrodeless discharge lamp (MWL): The microwave power output, spectrum of MWL, extinction of lights in dye solution and production of hydroxyl radical (·OH) and ozone (O3) are studied in detail. The results show that microwave field of 500W can kindle 9 pieces of MWUVL and power of MWL is about 60W. The spectral distribution of MWL is similar to middle-pressure mercury lamp. The intensity of visible light is equal to 500W conventional ultraviolet lamp (CUVL), but the intensity at 254nm ultraviolet light (UV) is about 20 times to CUVL. UV is absorbed more efficiently than visible light in dye solution. Production of·OH is related to the absorption of UV. The maximum penetrating distance of MWL is about 6cm. Quantity of O3 is exponentially enhanced with the increase of air and UV. Degradation of reactive red X-3B solution follows first order kinetics. The oxidative efficiency of MWL is obviously better than that of CUVL. In addition, significant synergistic effect of UV and generated O3 is observed.(2) Effect of temperature in microwave-photochemical process: The rule of microwave photochemical degradation at different temperature is investigated. The results show that the degradation rate follows first order kinetics and it is enhanced with the increase of temperature, but the relation between rate constant and temperature is incompatible with Aleniwus formula. The change of intensity of light has little effect on microwave photochemical degradation and no-thermal effect of microwave is the important reason for the increase of degradation.(3) Effect of oxidant on photochemical degradation: The combination of MWL and oxidant is studied. The results show that the rate of combination process is better than that of oxidatnt alone. The efficiency of oxidant is enhanced due to the synergistic effect between UV and oxidant. The sequence of the rate is UV/Fenton> UV/NaClO>UV/H2O2.