Degradation Of Polycyclic Aromatic Hydrocarbons By Non-thermal Equilibrium Plasma At Atmospheric Pressure

In recent years,the environmental pollution problem has become increasingly serious.Polycyclic aromatic hydrocarbons have attracted extensive attention due to their strong toxicity and carcinogenicity.This experiment was driven by a bipolar high-voltage nanosecond pulse power supply under atmospheric nitrogen and oxygen mixed gas conditions.The packed bed discharge and the non-packed bed discharge were generated,and the naphthalene was degraded by the plasma generated by the two discharges.The main research contents are as follows:1.The current and voltage waveforms and emission spectra of the two discharges were tested during the experiment.It was found that the discharge current of packed bed was higher than that of non-packed bed at the same voltage,and the emission spectrum intensity of nonpacked bed discharges in 300-420 nm band was higher than that of packed bed discharges.2.In the experiment of naphthalene treatment with two kinds of discharge,it was found that with the increase of pulse repetition frequency or pulse peak voltage,the energy input to the plasma region increased,and the degradation efficiency of naphthalene increased under both discharge conditions,but the energy yield decreased continuously.The efficiency of degrading naphthalene by non-packed bed discharge is higher than that of packed bed discharge.Under the condition of pulse peak voltage 28 kV pulse repetition frequency 120 Hz,the efficiency of degrading naphthalene by non-packed bed discharge reached 99.26%.3.The effect of oxygen concentration on naphthalene degradation was discussed by adjusting the ratio of nitrogen to oxygen.The results showed that when the oxygen concentration increased from 0% to 5%,the degradation efficiency of naphthalene increased significantly in both packed-bed and non-packed-bed discharges;when the oxygen concentration was 5-20%,the degradation efficiency increased gradually,and when the oxygen concentration was more than 20%,the degradation efficiency remained basically unchanged.4.The effect of gas flow rate(i.e.residence time)on naphthalene degradation was measured.The results showed that with the increase of gas flow rate(i.e.the decrease of residence time),the degradation efficiency of naphthalene by the two discharges decreased continuously.Under the same residence time,the degradation efficiency of the two discharges had little difference.The by-products of two kinds of discharge degrade naphthalene were analyzed by gas chromatography-mass spectrometry.It was found that under the condition of packed bed discharge,there were fewer degradation by-products and less secondary pollution.