A Synergistic Process Of Pulsed Discharge Plasma-Streamer Photocatalysis For Organic Pollutants Degradation In Aqueous Phase

In order to enhance the degradation efficiency of organic pollutants in a pulsed discharge plasma system and exert effect of streamer formed during a pulsed discharge process on organic compounds decomposition fully, we placed TiO₂ film photocatalyst supported on glass beads into a hybrid gas-liquid pulsed discharge plasma system with a multi-needle-to-plate electrode geometry to set up a pulsed discharge plasma-streamer photocatalysis sysem. The streamer was used as a lamp house to induce the photocatalytic activity of the TiO₂ in the pulsed discharge plasma system. The synergistic effect of pulsed discharge plasma-streamer photocatalysis on phenol decomposition and corrresponding mechanism were studied in this paper. The main results are summarized as follows:1. The streamer formed in the pulsed discharge plasma system could induce the photocatalytic activity of the immobilized TiO₂, and the synergistic effect of plasma-streamer photocatalysis on the organic compound degradation was achieved accordingly. The pseudo first order kinetic constant of phenol oxidation in the plasma-streamer photocatalysis system (k=2.4×10^-2 min^-1) was 1.4 times higher than that in the plasma alone system (k=1.0×10^-2 min^-1), under the condition of 100 mg/L concentration, 24 kV pulse voltage peak value, 4.0 capacitance, 50 Hz pulse frequency, 3 L/min air bubbling rate and 60 min treatment time. Corresponding removal rate of TOC increased 17.5%.2. The photocatalytic activity of the immobilized TiO₂ could be induced by the streamer under different experimental conditions. The reaction kinetic constants and energy efficiencies of phenol oxidation (G₅₀ values) in the plasma-streamer photocatalysis system with different gas bubbling varieties, initial solution pH values and radical scavenger additions (NaCO₃ and n-butanol), higher than those in the plasma alone system.3. The streamer could induce the light effect of the TiO₂. The radiant power of light with wavelengths of 200-500 nm in the plasma alone system was 6.45 mW, lower than the 8.14 mW of the plasma-streamer photocatalysis system bubbled with air, whereas the radiant power in the plasma alone system was 5.38 roW, lower than the 7.22 mW of the plasma-streamer photocatalysis system bubbled with O₂.4. The mineralization efficiency of phenol decomposition in the plasma-streamer photocatalysis system was higher than in the plasma alone system. Maximum concentrations of the three main byproducts (e. g. catechol, hydroquinone and benzoquinone) formed during phenol oxidation in the plasma-streamer photocatalysis system lower than those in the plasma alone system, and the corresponding time ahead.5. In the pulsed discharge plasma-streamer photocatalysis system, more oxidative species (H₂O₂,·OH and·O) could be generated through the induction of streamer on the photocatalytic activity of the TiO₂. The relative emission intensity of·OH and·O in the plasma-streamer photocatalysis system was higher than in the plasma alone system. H₂O₂ concentration in the plasma-streamer photocatalysis system was also higher.