Degradation Of Aniline By Coupling Process Of Photocatalytic Ozonation

Aniline,as an important organic chemical product,is widely used in the chemical and pharmaceutical fields.The obvious"three causes"effect makes it a serious threat to the environment and human beings after entering the water.It can not achieve good degradation effect through the commonly used biochemical process,which needs to be treated by strong oxidation.In recent years,advanced oxidation technology based on ozone has been widely used in the field of water treatment,and has become a research hotspot of advanced oxidation technology.Ozone has a strong oxidation capacity,which will not cause secondary pollution in the process of organic matter degradation.Due to the low solubility of ozone in water,the utilization rate of ozone is reduced,resulting in the high cost of advanced oxidation technology based on ozone.Photocatalytic technology is also an effective method to treat organic pollutants in water,which has the advantages of environment-friendly and low cost.However,there are some problems,such as low utilization rate of light energy and high selectivity of degradation of pollutants.In order to meet the requirements of low energy consumption and high efficiency operation,aniline was used as the target pollution source,and CQDs/TiO₂composite photocatalyst was used to construct the photocatalytic ozonation process system in this paper.The synergistic effect between the catalyst performance and the two technologies was investigated,and the mechanism of reaction was explored.The main research contents and results are as follows:（1）The CQDs/TiO₂composite photocatalyst was prepared by using activated carbon as the precursor of CQDs.The composite was characterized by SEM,TEM,XRD,FT-IR,XPS and electrochemical analysis.The photocatalytic performance of the CQDs/TiO₂composite was explored.The results showed that the degradation effect of aniline was the best when 10 m L CQDs solution was added,the removal rate of aniline was 95.8%in 8 min,which was 56.9%higher than that of nano-TiO₂.（2）Combined with ozonation technology,photocatalytic ozonation process system was constructed for degradation of aniline in simulated wastewater.The effects of initial aniline concentration,p H,inlet gas concentration of ozone and catalyst dosage in the coupling process were investigated.The results show that the degradation and mineralization of aniline by photocatalytic ozonation process is better than that by UV/O₃advanced oxidation system and ozone heterogeneous catalytic photocatalysis system.Combined with the first-order kinetics fitting results,the reaction rate constant of UV/O₃process is 2.97 min^-1,that of O₃/catalyst process is 2.60 min^-1,and that of UV/O₃/catalyst coupled process is 5.67 min^-1.When the initial concentration of aniline is 20 mg/L,the p H is neutral,the inlet gas concentration of ozone is 60 mg/L,the dosage of composite catalyst is 0.6 g/L,and the reaction time is 15 min,the removal rate of aniline is 99.8%and the mineralization rate is 76.8%.（3）The intermediate products in the degradation process of photocatalytic ozonation were detected by GC-MS.The intensity of active free radicals in the reaction was analyzed and compared by ESR.The production of hydrogen peroxide in the reaction was detected by fluorescence probe method.Combined with the above information,we can analyze the reaction mechanism of photocatalytic ozonation coupling process.The active radicals such as·OH and·O₂^-produced by the coupled process system are involved in the degradation reaction.Aniline is converted into aminophenol and aminophenyl radical under the action of active free radical,and then nitrobenzene or hydroquinone which is generated by further reaction,dehydrogenated to form benzoquinone.Benzoquinone is oxidized to small molecular acid,which is mineralized to CO₂and H₂O,realizing the efficient degradation of aniline.