Spectral Analysis of Oxygen Radical in a Synergistic System of Pulsed Discharge Plasma/TiO2
School of the Environment, Jiangsu University, Zhenjiang 212013, China.Guang pu xue yu guang pu fen xi = Guang pu (Impact Factor: 0.29). 01/2011; 31(1):58-61. DOI: 10.3964/j.issn.1000-0593(2011)01-0058-04
Based on the synergistic effect of pulsed discharge plasma and titanium dioxide (TiO2) photocatalysis, a coupling system of pulsed discharge plasma/TiO2 was set up in the present paper, by using the ultraviolet radiation produced during the pulsed discharge process. TiO2 film immobilized on the glass beads was used as the photocatalyst in the synergistic system. In the research, the synergistic mechanism of pulsed discharge plasma and TiO2 photocatalysis was reviewed by the spectral diagnosis of oxygen radical (* O radical) produced in different reaction systems. The obtained results showed that the characteristic emission spectrum of * O radical could be observed at 777 nm and the corresponding transitions was 3p5 P --> 3s5 S. When air was used as bubbling gas, the relative emission intensity of * O radical recorded in the synergistic system was stronger than that in the plasma alone system, and the same result was also obtained when oxygen (O2) was used as bubbling gas. This result revealed that the photocatalytic activity of the immobilized TiO2 in the synergistic system could be induced by the ultraviolet radiation formed during the pulsed discharge process. In the systems of pulsed discharge plasma alone and pulsed discharge plasma combined with TiO2 photocatalysis, the relative emission intensity of * O radical in distilled water was stronger than that in phenol solutions. The results showed that * O radical was one of responsible radicals for phenol degradation in the pulsed discharge plasma alone system as well as the synergistic system.
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ABSTRACT: Among the pollutants in soil, polycyclic aromatic hydrocarbons (PAHs) are the ones with high stability. Therefore, using pyrene, a typical PAH pollutant, as the object, we built a pulsed-discharge plasma-generating system with needles-to-net electrode geometry to treat soil polluted by pyrene, and investigated influences of the peak pulse voltage, pulse frequency, electrode distance, and air bubbling rate of the system on its efficiency in pyrene degradation. The sample of polluted soil used in the remediation system has an initial mass concentration of pyrene of 0.01%. The test results show that, in the system, the degradation rate of pyrene increases with pulsed peak voltage and pulse frequency, which is mainly due to the increase of output power. Meanwhile, increasing the distance between electrodes does not help to increase the degradation rate; the system has the highest degradation velocity with the distance of 10 mm. The degradation rate is higher at air bubbling rate of 1 L/min than at 0 and 2 L/min.
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