| Dielectric barrier discharge plasma(DBD)as a non-equilibrium plasma,which has the characteristics of both glow discharge with large space uniform discharge and high pressure operation of corona discharge.This experiment was to explore the possibility of plasma and biological trickling filter in coupling of the tower.Hence,DBD reactor was adopted in our experiments,the degradation of chlorobenzene with DBD was studied under different condition,such as the peak voltage,inlet concentration,humidity and residence time and other parameters.The amount of ozone produced by the discharge was measured,degradation intermediate substances were identified,and the solubility,biodegradability and biological toxicity of the exhaust-gas were researched,which were provided a theoretical basis for the follow-up biological trickling-filter tower operation.Furthermore,some improved methods,such as catalyst addition or carrier-gas changing,were conducted to reduce the energy consumption for chlorobenzene degradation and to improve the chlorobenzene removal rate as well as the amount of 03,solubility,biodegradability and toxicity of the productions.In this study,the optimal process conditions for chlorobenzene degradation with DBD reactor were obtained:the SIE at 18 kJ·L-1～32 kJ·L-1,mixed-gas residence time of 10 s,relative humidity between of 65%～75%.With increasing of the inlet concentration of chlorobenzene,the removal rate was decreased.When the inlet concentration of chlorobenzene was 100 mg·m-3,the removal rate was 95%;When the inlet concentration of chlorobenzene was 2000 mg·m-3,the removal rate was 85%,the removal rate was 10%decreased.But the amount of chlorobenzene was increased,the maximum amount was 1900 mg·m-3.Meanwhile,the concentration of ozone in the exhaust gas was increased with the increase of peak voltage.The minimum and maximum amount of 03 were 0.1 mg·L-1’ and 1.4 m·-L-1,which reflect the amount of 03 had inhibition effect on biomass growth in the biological trickling filter tower.With the increased of SIE,the value of TOC was increased,which meant the production had good water soluble.When SIE≥18 kJ·L-1,the value of B/C was more than 0.3,which meant the production could be degraded by the microorganisms.Comparing with the control-group,the growth of the chlorella was inhibited when SIE was 7 kJ·L-1,had no effect when SIE was 19 kJ·L-1,and had been promoted when SIE was 35 kJ· L-1.The main production of the discharge were detected by GC/MS,the main productions were alcohols,acids,ketones and straight-chain alkanes,which was suggested that chlorobenzene was not degraded entirely to C02 and H20 by DBD.Hence,the results showed that it was necessary to couple DBD with BTF for chlorobenzene degradation.Furthermore,two different improvement methods,catalyst addition or carrier-gas changing were adopted.The experiment showed that catalyst added could increase the removal rate of chlorobenzene.When the amount of catalyst were 0 g,0.2 g,0.5 g,SIE was 18 kJ·L-1,resident time was 10 s,relative humidity between of 65%～75%,the removal rate of chlorobenzene were 80%、83%and 90%respectively.Compare to control-group(80%,air as the carrier-gas),the removal rate of chlorobenzene were increased to 90%when N2 was adopted as carrier-gas.The amount of 03 was decreased when the amount of catalyst were 0.2 g and 0.5 g,and the maximum amount of 03 was 0.4 mg·L-1.The value of TOC was increased by catalyst added and carrier-gas changed,which meant that the water soluble was increased.Meanwhile,the biodegradability was also enhanced.However,the biological toxicity was different.The catalyst contained metal,which could be soluble in water and then be absorbed by chlorella,so the catalyst had toxicity to microorganism in BTF.The results obtained in these experiments could prove the theoretical basis for coupling the DBD with BTF. |
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