Study On Mineralization Effect Of Vacuum Ultraviolet On Chlorinated Aromatic Hydrocarbons And Oxygenated VOCs

Volatile organic compounds(VOCs)have a wide range of sources and complex components,which not only seriously endanger the atmospheric environment,but also adversely affect human health.Since the chemical properties of most VOCs are relatively stable,it is difficult to completely degrade them by conventional treatment methods,and it is easy to cause secondary pollution problems.Vacuum ultraviolet photolysis technology is an emerging and efficient method for the treatment of gaseous pollutants.This technology utilizes high-energy UV light to provide a possibility for thorough mineralization of VOCs.However,the current research on the treatment of VOCs by vacuum ultraviolet photolysis technology is limited to some common indoor pollutants,and the research on mineralization effect and mixed treatment effect is relatively scarce.In view of the above problems,this thesis studied the effects of vacuum ultraviolet on the individual and mixed mineralization of various VOCs by using chlorinated aromatic hydrocarbons and oxygenated VOCs as research objects.The subject establishes a vacuum ultraviolet reaction system that can realize cyclic mineralization.By investigating the influence of ultraviolet wavelength,initial concentration,relative humidity,oxygen content and other influenci ng factors on the benzyl chloride mineralization effect,the reaction conditions were optimized and a preliminary exploration of the mechanism of vacuum ultraviolet photolysis was realized.When the irradiation time is not enough to completely mineralize benzyl chloride,the mineralization effect of benzyl chloride is significantly affected by the initial concentration,and the mineralization rate and degradation rate of benzyl chloride decrease with the increase of initial concentration.In addition,increasing the relative humidity and oxygen content is beneficial to promote the mineralization of benzyl chloride.In the vacuum ultraviolet photolysis of benzyl chloride,direct photolysis dominates,and increasing relative humidity is more conducive to promoting the mineralization of benzyl chloride than increasing oxygen content.Through the investigation of the UV mineralization effects of various VOCs,it was found that in addition to methyl isobutyl ketone,several chlorinated aromatic hydrocarbons and oxygenated VOCs can achieve a mineralization rate of more than 90% under vacuum ultraviolet conditions.The conditions for the mineralization of methyl isobutyl ketone were re-optimized from the aspects of oxygen content and relative humidity.The results sho w that the adjustment of relative humidity is more conducive to promote the mineralization of methyl isobutyl ketone than increasing the oxygen content.The influence of material structure and the reactivity of functional groups on the mineralization effects of VOCs were obtained.The simpler the structure of VOCs,the stronger the reactivity of functional groups,the easier it is to be mineralization reaction.Vacuum UV has good applicability to the treatment of mixed gaseous pollutants containing various VOCs.The mixing ratio has a significant effect on the mixed mineralization effect.Taking mixed mineralization of methyl isobutyl ketone with benzyl chloride or methyl isobutyl ketone with benzaldehyde as an example,the higher the mixing ratio of benzyl chloride or benzaldehyde in the mixed components,the better the overall mixed mineralization effect.In addition,mixed mineralization can improve the mineralization effect of difficult mineralized substances,and the mineralization effect of methyl iso butyl ketone in the mixed components is significantly improved compared with UV photolysis alone.