以低压汞灯为光源,采用石英管连续流动态反应系统和特氟龙气袋静态反应系统,研究了环境因素〔RH(相对湿度)、温度、光照强度、有氧(空气)/无氧(氮气)气氛条件〕对低浓度(10~20 mg/L)气相甲苯光氧化过程的影响.结果表明:1RH对甲苯光氧化反应影响显著.干燥条件(RH为0%~5%)下甲苯光氧化去除率在8.3%~8.7%之间;当环境中有水蒸气存在(RH为20%)时,甲苯光氧化去除率降至6.5%~7.2%,其后光氧化去除率随着RH的进一步增加而逐渐增大,在RH为60%时达到最大值(9.4%~11.5%);但当RH继续增至80%时,去除率迅速降至4.4%~5.6%.2甲苯光氧化去除率随着温度、光照强度的增加而提高.3无论是干燥(RH为0%~5%)还是湿润(RH为60%)环境下,甲苯在有氧气氛下的去除率均高于无氧气氛;甲苯在有氧气氛下光氧化产物主要是苯和苯甲醛,在无氧气氛中的产物主要是苯.4在干燥、有氧条件下,O(1D)应是甲苯光氧化的活性物种;在湿润、有氧条件下,甲苯的光氧化主要是通过·OH氧化降解;在无氧条件下,甲苯的光氧化主要是通过甲苯的直接光解完成.
The photooxidation of gaseous toluene using a low-pressure mercury UV lamp as the irradiation source was described. The influence of environmental factors, such as relative humidity (RH), temperature (T), light intensity (I) and aerobic/anaerobic atmosphere on the photooxidation efficiency of toluene with low concentrations ( 10-20 ng/L) were studied in a quartz tube reactor using a dynamic experiment system. The intermediate products generated during the photooxidation of toluene were studied in the Teflon reactor using a static experimental system. The experimental results indicated that: 1) RH significantly affected the toluene photooxidation. The removal rates of toluene were between 8.3% and 8.7% under the drying condition (RH -0% -5% ). When water vapor was introduced into the air, the removal rate of toluene was reduced to 6. 5%-7.2% (RH = 20% ). With the increase of RH, the photooxidation removal rate of toluene also increased, and the peak removal rates of toluene were between 9.4% and 11.5% under RH = 60%. When RH increased to 80% , the removal rate of toluene was rapidly reduced to 4. 4% to 5.6%. 2) The photooxidation removal rate of toluene tended to improve with the increase of environmental temperature or light intensity. 3 ) The removal rate of toluene in the aerobic atmosphere (air) was higher than that in the anaerobic atmosphere (nitrogen) in both dry (RH = 0%-5% ) and humid environments (RH = 60% ). The intermediate of photooxidation of toluene in the nitrogen medium was benzene, while the intermediates in the air medium were benzene and benzaldehyde. 4 ) Under the aerobic dry atmosphere, the active species of photooxidation of toluene were perhaps 0 (^1D), while it was .OH in humid environment. Under the anaerobic atmosphere, the removal of toluene was mainly derived from the direct degradation by UV ( 185 nm) irradiation.