In our laboratory, we developed a new type nonthermal plasma reactor in which a porous ceramic filter and surface corona discharge induced plasma chemical process (SPCP) are combined, and have been examined its applicability for VOCs (volatile organic compounds) decomposition in gas and water treatment. In the previous study, we demonstrated that various VOCs were almost completely decomposed using the reactor due to the very high contact efficiency of VOC gases with plasma, which is the main feature of our system. In this study, we examined the effect of electrode configuration and power frequency on TCE (trichloroethylene) decomposition and also tried to clarify its mechanism.
The reactor consists of the tubular ceramic filter, a rod electrode which is inserted into the ceramic filter and a thin wire electrode which is wound at equal intervals around the surface of the ceramic filter. In the experiment, TCE decomposition was tried by changing the distance between wires (pitch) wound around the filter and power frequency. The result showed that the TCE decomposition was improved by optimizing the pitch length and by the lowering power frequency. Then, we tried to clarify the mechanism of the improvement. In our reactor, introduced TCE is decomposed through three different discharge modes such as surface, void and barrier discharge. Although the reactor was designed to utilize the surface discharge mainly to decompose gaseous pollutants, actually the void discharge in the ceramic pores and the barrier discharge between inner surface of the ceramic filter and the center electrode were also considered contributing to decompose VOCs. Therefore, contribution ratio of the surface-void discharge and the barrier discharge in each electrode configuration and power frequency was measured. The results showed that the electrode configuration and the power frequency significantly affect the contribution ratio of each discharge and then affected the TCE decomposition.