Degradation of Benzene by a Falling Film Gas-Liquid Phase DBD Plasma with Persulfate

Dielectric barrier discharge (DBD) plasma has been proven to be a promising method for the decomposition of VOCs, but the treatment process of VOCs also released gaseous byproducts including organic aerosols and NOx. A falling film gas-liquid phase DBD reactor was successively used to degrade benzene, during the process, benzene mainly reacts with the reactive species from gas phase electric discharge and then the gaseous products including NOx, dissolvable organic aerosols, etc. can be removed via the absorption and aqueous plasma reactions into a water film. Moreover, persulfate was added into the circulating water solution for enhancing the degradation of pollutants. The effect of pulse frequency, persulfate dosage, solution recycling rate, and solution initial pH value on benzene degradation was studied. Experimental results indicate that an addition of persulfate into water decreased total organic carbon (TOC) in the solution, very interesting, benzene degradation efficiency was also increased, possibly due to an enhancement on those water surface plasma reactions and the diffusion transfer of benzene into water film. Moreover, increase in the total nitrogen (TN) in solution proved the absorption of gaseous NOx into water. EPR spectroscopy shows an increase in the reactive radicals including SO4(middot-) , middotOH, indicating an feasible activation of persulfate by discharge plasma. Radical scavenging experiments indicate that SO4(middot-) , middotOH, and O-1(2) contributed to the degradation of benzene, and e(aq) contributed to the activation of persulfate into reactive radical species.