Research On Deep Treatment Of Aniline Wastewater By Heterogeneous Catalytic Ozonatio

Aniline is one of the common raw materials in the production and use of dyes.Printing and dyeing wastewater containing aniline will cause great harm to the environment and body health.It is of great significance to explore the green and efficient process for the treatment of aniline for the environment and biological safety.Heterogeneous catalytic ozonation has a good effect on the removal of organic pollutants and has a broad application prospect in the treatment of aniline.In this study,heterogeneous catalyst was prepared to catalyze ozone,and the degradation effect of aniline was used as the main evaluation basis of catalyst performance,and the optimal preparation and operation conditions of catalyst were explored to obtain the best degradation effect of aniline.The heterogeneous catalyst was prepared by selecting Al₂O₃ pellets as catalyst carrier and Mn,Co and Ni transition metals as active components.The experimental results show that when the preparation conditions of spherical catalyst are:after alkali activation pretreatment,Mn/Al₂O₃ prepared by constant volume impregnation method at the calcination temperature of 500℃,calcination time of 4 h,the precursor impregnation solution of 1.5 mol/L manganese nitrate solution has the best catalytic performance of ozone,aniline has the best degradation effect,Mn:Ni=1.5:0.15performance is the second.And then a solution of cobalt nitrate and nickel nitrate at 1.0mol/L.The characterization of Mn/Al₂O₃ shows that Mn oxide is uniformly dispersed in granular form on the surface of the carrier,and the number of specific surface area and surface hydroxyl group increases to a certain extent.Through test element and valence,Mn+2,+3,+4 valence state exists,and+4 Mn in a dominant position,in addition,increasing oxygen adsorption(O_ad)is beneficial to the catalyst surface redox reaction,improve the catalytic performance of catalyst,so the above results showed that the addition of Mn catalytic ozone effectively,on the degradation of aniline has the best effect.The plate ceramic membrane（FCM）catalyst was prepared according to the best preparation conditions of spherical catalyst.The experimental results confirmed that Mn/FCM catalyst prepared with FCM as the carrier showed the best catalytic ability of ozone.However,by analyzing the characterization results,it was found that Mn oxide was too dispersed on the surface of FCM,and the specific surface area of Mn/FCM and the number of surface hydroxyl groups did not change significantly.By testing the types and valence states of elements,it can be seen that Mn mainly exists in+2,and the content of Mn in+3 and+4 valence states is low,which is not conducive to the redox reaction on the catalyst surface.By contrast,Mn/Al₂O₃ is more conducive to catalyzing ozone.The degradation of aniline by two heterogeneous catalysts at different pH values,ozone flow rate and aniline concentration was further investigated.It was found that aniline degradation was the best when the initial pH was 9.Aniline concentration was20 mg/L,and the degradation effect was inversely proportional to aniline concentration.The ozone flow rate was in direct proportion to the aniline degradation effect,and the best degradation effect was obtained when the ozone flow rate was 1.0 L/min.The mechanism of heterogeneous catalytic ozonation was investigated,and it was found that Mn/Al₂O₃ and Mn/FCM could promote the generation of·OH and O₂^·-.The macrodynamics model was used to fit the influencing factors of aniline degradation by heterogeneous catalyst.The catalytic performance of Mn/Al₂O₃and Mn/FCM was evaluated according to the apparent reaction rate constant.It was found that the apparent reaction rate constant of Mn/Al₂O₃ was higher than that of Mn/FCM under the influence of pH,ozone flow rate and aniline concentration,which proved that Mn/Al₂O₃ had stronger catalytic performance.