Enhancement of Active Species Formation by ${\rm TiO}_{2}$ Catalysis in the Bipolar Pulsed Discharge Plasma System

In the process of water treatment by bipolar pulsed discharge plasma, there are not only the chemical effects such as the active species formed in the plasma channel, but also the physical effects like the ultraviolet radiation. Power energy consumed in form of optical radiation can be used by photocatalyst to improve the energy efficiency of the discharge system. Therefore, the effects of the photocatalyst on the formation of active species and degradation of the organic pollutant in the packed bed plasma reactor were studied in this paper. The nanoparticle TiO₂ photocatalyst was obtained using the sol-gel method, structure and characteristics of TiO₂ films were investigated via X-ray diffraction and scanning electron microscope. Formation of H₂O₂ and O₃ under different conditions (applied voltage, air flow rate, diameter of solid packing, etc.) in the plasma and hybrid plasma-catalysis system was investigated. The experimental results proved that the combination of the pulsed discharge plasma process with TiO₂ catalysis enhanced concentration of active species generated, and improved water treatment efficiency. In addition, the synergistic effect on H₂O₂ and O₃ concentration increased with the increase of applied voltage, the gas flow rate and the amount of TiO₂ photocatalyst. A small part of the TiO₂ film fell off rough surface of the glass beads even after 5-h electric discharge treatment, and then remained almost constant. No obvious differences were found in the removal rate of indigo carmine after the catalyst loss.