Study Of The Benzene Degradation Performance In A Double Chamber Gas-liquid Phase Dielectric Barrier Discharge Reactor

The emission of volatile organic pollutants?VOCs?can seriously endanger the ecological environment quality.Compared to other VOCs treatment methods such as photocatalysis,catalytic combustion,biological and so on,non thermal plasma/catalysis technology has the advantages of high efficiency,non-selectivity and widely application fields,but the degradation of VOCs by gas phase discharge?catalysis?alone also has the problem of harmful byproduct emissions.In this paper,a double chamber gas-liquid phase DBD reactor?GLDR?,consisting of a gas phase discharge chamber?GDC?and a gas-liquid discharge chamber?GLC?in series,was designed for VOCs treatment.Benzene was selected as one of typical VOCs in this paper.In GLDR,VOCs entered the gas discharge chamber and gas-liquid phase discharge chamber for sequential treatment in order to control the gas phase byproduct emission during the purification of VOCs.At the same time,in order to enhance the benzene degradation efficiency,the effect of persulfate on the benzene degradation was studied.In addition,the benzene degradation and byproduct control performance of GLDR/Cu_x-Mn_y/?-Al₂O₃ system were also studied,and the effects of electrode structure,applied voltage,air and solution parameters on benzene degradation were investigated.The performance of benzene degradation and byproduct production of GPDR and GLDR were compared.The main results are as follows:?1?The GLDR presented higher benzene degradation,energy yield,active species production?O₃ and H₂O₂?and NO_x control than that of the GPDR.At 15 kV,the degradation efficiency and the energy yield of GLDR was 19%and 0.39 g/kWh higher than that of GPDR,respectively.The benzene degradation efficiency increased with the applied voltage,but decreased with the initial concentration,gas flow rate,and gas discharge gap,and the solution conductivity and solution pH value presented little influence on benzene degradation.The benzene degradation efficiency and energy yield reached 61.11%and 1.45 g/kWh at 15 kV applied voltage,4 mm total gas discharge gap,200 ppm benzene concentration,0.2 L/min gas flow rate,721?S/cm water conductivity and 7.02 pH value.With the addition of 3 mmol/L K₂S₂O₈ and KHSO₅,the benzene degradation efficiency was increased by 7.4%and 9.1%,respectively.The intermediates and byproducts during benzene degradation were detected by FT-IR,GC-MS and HPLC-MS.According to these detected byproducts,a possible benzene degradation mechanism was proposed.?2?For GLDR/Cu_x-Mn_y/?-Al₂O₃ system,the effects of different ratios of Cu/Mn catalysts on benzene degradation efficiency,energy yield,CO₂ selectivity,O₃ and NO₂ production were investigated.Among these catalysts,Cu-Mn/?-Al₂O₃?1:1?catalyst had the highest benzene degradation efficiency and CO₂ selectivity.At the applied voltage of 15 kV,4 mm total gas discharge gap,100 ppm benzene concentration,0.2 L/min gas flow rate,5750?S/cm solution conductivity and 7.02 pH value,the degradation efficiency of benzene was 85.03%and the selectivity of CO₂ was 71.34%,26.91%and 34.87%higher than that of GLDR,respectively.With the addition of 3 mmol/L K₂S₂O₈ and KHSO₅,the benzene degradation efficiency increased by 12%and 14.50%,respectively.In addition,the effects of catalyst loading,space velocity of catalyst and carrier gas humidity on benzene degradation efficiency were investigated.The results showed that the increase of the catalyst loading and the decrease of the space velocity of catalyst in a certain range improved the benzene degradation efficiency;and the suitable relative humidity of carrier gas also improved the benzene degradation efficiency.The solution pH value presented a little influence on benzene degradation efficiency.The discharge byproducts before and after plasma binding to catalyst were analyzed by FTIR.