多相脉冲放电体系中羟基自由基的光谱诊断

Spectral Diagnosis of Hydroxyl Radical in Multiphase Pulsed Discharge System

采用多针-板电极形式的气液混合脉冲放电系统,在其中加入玻璃珠负载的TiO2膜光催化剂形成了一个气-液-固多相脉冲放电体系,研究中利用脉冲放电过程中产生的紫外光效应诱导其中的TiO2的光催化作用,通过对放电体系中羟基自由基(.OH)的光谱诊断考察TiO2光催化作用与脉冲流光放电的协同作用效果。结果表明,本脉冲放电体系中产生的.OH在306 nm(A2Σ+→X2Π跃迁)、309 nm(A2Σ+(ν′=0)→X2Π(ν″=0)跃迁)和313 nm(A2Σ+(ν′=1)→X2Π(ν″=1)跃迁)处均产生发射光谱,其中313 nm处的.OH的光谱强度最强;脉冲放电协同TiO2光催化作用系统中.OH的发射光谱强度较单独的脉冲放电体系强,同时,条件实验(不同鼓气种类和水溶液初始pH值)的研究结果表明用氩气作为鼓气源时,多相反应体系中313 nm处.OH的发射光谱强度比以空气和氧气作为鼓气源时的强度高,酸性溶液中313 nm处.OH的发射光谱强度比中性和碱性溶液中高。

A gas-liquid hybrid pulsed discharge system with a multi-needle-to-plate electrode geometry was used in the present study. A multiphase （gas-liquid-solid） pulsed discharge system was then formed by adding glasses beads immobilized with TiO2 photocatalyst into the discharge system. In the present paper, ultraviolet light produced during the pulsed discharge process was used as the lamp-house to induce the photocatalytic activity of the TiO2 photoeatalyst. The synergistic effect of pulsed discharge and TiO2 photocatalysis was reviewed by the spectral diagnosis of hydroxyl radical （ ·OH） in the pulsed discharge system. The obtained results showed that the emission spectrum of ·OH could be observed at 306 nm （A2Σ＋→X2Π）, 309 nm （A2Σ＋（ν′=0） →X2Π（ν″=0）） and 313 nm A2Σ＋（ν′=1）→X2Π（ν″=1） transition）. The relative emission intensity of ·OH at 313 nm in the discharge system was the strongest among the three characteristic spectra. The relative emission intensity of ·OH at 313 nm was stronger by adding TiO2 photoeatalyst into the pulsed discharge system than that in the sole pulsed discharge system. In the case of experiments that changing the gas bubbling varieties and initial solution pH values, the results revealed that the relative emission intensity of ·OH at 313 nm in the synergistic system was stronger when Ar was used as bubbling gas compared with that when air and oxygen were bubbled into the reaction system. Furthermore, the acidic solution system was favorable for producing more ·OH, and therefore the corresponding emission intensity of ·OH at 313 nm was stronger than that in the neutral and basic solution.