Degradation Of High Toxic Small Molecule Wastewater By Vacuum Ultraviolet Coupled With Chemical Oxidation

Environmental issues have always been a major concern of global.Water pollution becomes more and more serious with untreated domestic sewage and industrial wastewater having not meet emission standards but enter the water directly.The wastewater containing organic small molecule pollutants has always been a difficult point in water treatment for trait of biochemical degradation difficultly,high toxicity and high COD.Catalytic Wet Hydrogen Peroxide Oxidation is an effective means for treating organic wastewater with high concentration and difficult degradation by hydroxyl radicals（?OH）under normal temperature and pressure.The organic can sensitized and the chemical bond can broken easily through vacuum ultraviolet technology.In this paper,small molecule wastewater with highly toxic is treated by vacuum ultraviolet coupled chemical oxidation method.A large amount of hydroxyl radicals（?OH）generated by synergistic action are used to make the chemical bond broken and oxidize organic matter.Eventually the organic matter turns into water and carbon dioxide,which are environmentally friendly.Therefore,small molecules such as formaldehyde,acetonitrile and melamine are used to degraded,the composite catalyst with the best degradation effect was searched and process optimization experiments was carried to obtain the best conditions for degradation.Firstly,the composite catalyst was prepared by impregnation method and the formaldehyde wastewater with high-concentration was treated by vacuum ultraviolet coupled chemical oxidation method（CWPO/H₂O₂/VUV）,where in H₂O₂ was used as an oxidant to provide hydroxyl radicals（·OH）required for the reaction and ultraviolet light energy was applied.The comparison of different catalyst treatments by laboratory experiments showed that the composite catalyst CuO-ZrO₂-CaO/γ-Al₂O₃（3%-1%-1%）had the best performance and various characterization methods（Fourier Transform Infra-Red spectroscopy（FT-IR）,X-ray Powder Diffraction（XRD）,Scanning Electron Microscope（SEM）and Energy Dispersive X-ray spectroscopy（EDS）,Nitrogen Adsorption-desorption test（BET））were used to the characterization of catalysts.In the degradation process,COD degradation rate（%）,absorbance degradation rate（%）,and residual water concentration（mg/L）were used as indicators for evaluating catalyst activity.The effects of initial concentration of wastewater,amount of catalyst,pH of solution,amount of H₂O₂,reaction temperature on degradation reaction were investigated and the best experimental treatment process were obtained.The experimental results show that the high-concentration formaldehyde wastewater can be degraded by CWPO/H₂O₂/VUV coupling process.In this experiment,350 mg/L formaldehyde wastewater is used as the treatment target and the degradation rate can reach 100%when the reaction time is 20 min under neutral conditions and the reaction temperature is 30°C,the catalyst dosage is 2 g and the H₂O₂ dosage is 5 ml.Similarly,the high-concentration acetonitrile wastewater and melamine wastewater were degraded by vacuum ultraviolet coupled chemical oxidation（CWPO/H₂O₂/VUV）and the degradation effects were investigated from the aspects of catalyst dosage,solution pH,H₂O₂ dosage and reaction temperature.The experimental results show that the acetonitrile wastewater and melamine wastewater can be degraded by coupling technology under no strict conditions and the degradation rate is high,which can effectively remove COD in a short time.Among them,the degradation rate of acetonitrile simulated wastewater can reach 99.8%,and the degradation rate of melamine can reach 92.5%.