Break Of Benz[a]Anthracene By Hydrodynamic Cavitation And Chlorine Dioxide

Benz[a]anthracene,as one of the priority control of polycydic hydrocarbon pollutants,possesses of caicinogenicity,teratogenicty and mutagenicity effects,it is widely existed in the environment and seriously affects human health.Hydrodynamic cavitation,as a efficient method,has achieved great results in wastewater treatment.For the first time,hydrodynamic cavitaion was combined with chlorine dioxide which was applied to degrade the benz[a]anthracene,respectively using separate hydrodynamic cavitation,chlorine dioxide and the combined technology to degrade the benz[a]anthracene.Explored the effects of different elements on the removal of benz[a]anthracene,and determined the optimal parameters and operating conditions.The degradation products of benz[a]anthracene were analyzed by high performance liquid phase（HPLC）and gas chromatography-mass spectrometry（GC-MS）technology.Meanwhile the kinetics of different degradation methods were discussed.The main research results were as follow:（1）The study of hydrodynamic cavitation degradation of benz[a]anthracene was based on the orifice plate to explore the effects of different factors on the degradation of benz[a]anthracene.The results showed that the orifice（orifice opening rate of 0.066,annular configuration plate）achieved the best effects.The inlet pressure of 0.4MPa and the reaction time of 2h,the degradation rate of benz[a]anthracene reaches its maximum at 41.67%.By analyzing the degradation products,the main products of this treatment processess were7,12-dihydroxybenz[a]anthracene and benz[a]anthracene-7,12-dione.（2）In the study of degradation of benz[a]anthracene by chlorine dioxide alone,the optimal reaction conditions were:the concentration of chlorine dioxide was 25mg/L,the reaction time was 2h,under the conditions,the degradation rate was the best,90.5%.And the main product is benz[a]anthracene-7,12-dione..（3）In the study of degradation of benz[a]anthracene by hydrodynamic cavitation combined with chlorine dioxide,Using Design-Expert to design the experiment plans,establish the multiple regression equation and carried on the analysism finally optimize the experiment conditions.The results showed that the degradation rate of benz[a]anthracene increased of the reaction time and concentration of chlorine dioxide,the regular of inlet pressure to the degradation reta of benz[a]anthracene showed that increasingfirst then decrease.The conditions of optimized were:the concentration chlorine dioxide of 24.6mg/L,the reaction time of 125min,the inlet pressure of 0.4MPa,and the degradation rate of benz[a]anthracene was 99.9%under the optimized coditions.The main degradation products were7,12-dihydroxybenz[a]anthracene,5,6-dihydroxybenz[a]anthraxcene,benz[a]anthracene-5,6-dione,benz[a]anthracene-7,12-dione,2-（4-carbaldehyde-phenyl）-3-carbaldehyde-naphthalene 1-benzoyl-naphthalene-2-carbaldehyde.Through calculating,the combination of hydrodynamic cavitation and chlorine dioxide to degrade benz[a]anthracene accorded with the first-order kinetics,the kinetic rate constant was 6.58×10^-4s^-11 and the half-life was 17.55min.Compared with the two separate degradation technologies,the combined process had synergistic effect on the degradation of benz[a]anthracene,and its synergistic coefficient was 1.48.