Process Characteristics And Mechanism Of Coupling System Consisting Of DBD With Catalysis And Biotrickling Filter For Chlorobenzene Removal

As an important component of industrial emissions of chlorinated VOCs,chlorobenzenes(CB)is more chemical stable compound with three adverse effects For the low water soluble and not easy-biodegradable VOCs,biopurification is difficult to achieve the ideal effect.Therefore,the development of suitable chemical oxidation-biological purification technology has become a research tissue for the treatment of the type waste gas.In this study,a dielectric barrier discharge(DBD)combined with catalyzer as the pretreatment,was coupling with biopurification together,for the treatment of CB.By preparing three catalysts(CuO/MnO2,CeO2/HZSM-5,Ag/TiO2),their enhanced effects on CB conversion by DBD were investigated.Especially,the conversion of CB and its intermediates' water solubility and biodegradability were studied in detail under the low energy density input conditions.In the coupling system,CuO/MnO2 was selected as the catalyst,and a coupling system composed of DBD and biotrickling filter(BTF)was built up.Compared with the single BTF,the removal performance of both the system and the different microbial community structure in the BTFs were conducted.Through the characterization of XRD,BET,EDS and other methods,the results showed that both the catalyzers CuO/MnO2 and CeO2/HZSM-5 were a mixture of phase,and Ag/TiO2 for single phase;CeO2/HZSM-5 had specific surface area and pore volume larger than the other two catalysts,and all the doped elements were involved into the catalyst carrier.There were water or O-H bond characteristic absorption peaks existing on the catalyst surface,which provided a chance for more active substances(such as OH-)producing.Under the same energy density input,DBD combined with three catalysts for the transforming effect of CB were higher than that of single DBD,and the energy utilization rate of single DBD,DBD with CeO2/HZSM-5,CuO/MnO2 and Ag/TiO2 was 0.423,0.950,0.925 and 0.698 g·(kw·h)-1 The stability test showed that the catalyzer CeO2/HZSM-5 was much more stable and the CB conversion efficiency had been maintained at 72%during 40h;while the performance of other two catalyzer decreased slightlyConsidering the complexity and price of catalyst preparation process,40%CuO/MnO2 was chosen as the catalyst in DBD process,and analyzed different input energy density of DBD combined with CuO/MnO2 for the transforming of CB.In the relative humidity of 50%,the conversion efficiency of CB increased with the increase of the peak voltage and residence time.When the residence time and peak voltage were 5s and 3kV,the energy utilization rate of the whole system was larger(about 0.0768 mg·kJ-1);when O2 content in the reaction medium of 15%and the peak voltage of 3KV,the energy utilization rate reached 0.1424 mg-kJ-1.With the input energy density of 1.3-3.5×103J·L-1,the soluble components accounted for 49%of CB conversion amount,and B/C(the ratio of BOD5 and COD)of the absorption liquid was 0.385A coupling system of DBD(using CuO/MnO2 as the catalyst)and BTF was set up.By utilizing the proper condition of DBD combined with catalysis,the coupling BTF could startup successfully in nearly 13 d inoculated with an efficient degradation bacterium Ralstonia pickettii H2 and acclimated activated sludge.With the same inoculum,the single BTF could be startup 2 d longer and the removal efficiency of CB was 97%(lower than that obtained by DBD-BTF).During the stable operation period with the same EBRT(Empty bed residence time),the performance of single BTF was almost similar with that of coupling system when the concentration of CB was lower.But when the concentration increased up to 900 mg·m-3,the coupling system had a better performance over than the single BTF.With a shorter EBRT of 45s,the coupling one was better than the single on no matter what the concentration of CB was.The mineralization rates of both system were 95%and 86%respectivelyBy analyzing the contribution to CB removal of each function unit,DBD combined with CuO/MnO2 was mainly responsible for conversion of CB,the bottom section of BTF was responsible for the mineralization of intermediates produced by pretreatment,and the upper for the remaining CB removal and mineralizationMicrobial richness were greater in the coupling BTF.The Shannon index of the bottom and upper packing materials in the single and coupling BTF were 3.11,3.89,3.13 and 3.38,respectively.The main microorganisms belonged to the class Betaproteobacteria and Alphaproteobacteria,Flavobacteriia,Gammaprotebacteria and Sphingobacteriia,but their amounts were different from each other.The main reason for these was the composition of the exhaust gas.