碳纳米管负载TiO_2对1,2,4-三氯苯的光降解研究

Photocatalytic Degradation of 1,2,4-Trichlorobenzene with TiO_2 Coated on Carbon Nanotubes

碳纳米管负载TiO2复合光催化剂与纳米TiO2光催化剂对1,2,4-三氯苯的光催化降解效果,及降解动力学的研究结果表明,复合光催化剂比纳米TiO2有更好的光催化降解效果,经254 nm紫外光辐照60 min后,使用复合光催化剂的1,2,4-三氯苯降解了70%,而使用纳米TiO2为催化剂的1,2,4-三氯苯仅降解了51%;光催化降解动力学研究也表明复合光催化剂对1,2,4-三氯苯光催化反应速率常数为0.019 6 h-1,比纳米TiO2提高了63.3%.根据分子结构理论,对氯苯化合物的C—Cl键离解能分析可推测1,2,4-三氯苯的主要光降解路径为:先脱去邻位的Cl生成1,4-二氯苯,然后再进一步脱氯,最终彻底矿化.通过实验检测1,4-二氯苯作为1,2,4-三氯苯的产物已证实了其第一步脱氯过程.

Effects and kinetics of photocatalytic degradation of 1,2,4-trichlorobenzene with composite photocatalysts of TiO2 coated on carbon nanotubes and nano-TiO2 photocatalysts were studied,respectively.It was found that the composite photocatalysts was better than the nano-TiO2 for photocatalytic degradation of 1,2,4-trichlorobenzene.After 60 min UV irradiation at 254 nm,there was 70% of the initial 1,2,4-trichlorobenzene degraded with the composite photocatalyst while only 51% of the initial 1,2,4-trichlorobenzene degraded with the nano-TiO2.Results of photocatalytic degradation kinetics also proved that the 1,2,4-trichlorobenzene degradation rate constant with the composite photocatalyst was 0.019 6 h^-1,which was increased by 63.3% compared to that with nano-TiO2.According to molecular structure theory,analysis of dissociation energy of C—Cl bond of chlorobenzenes predicated that main pathway of photocatalytic degradation of 1,2,4-trichlorobenzene followed that its ortho-Cl could be took off first to form 1,4-dichlorobenzene,and it might be further dechlorized and finally be mineralized.The first step of photodechlorination for 1,2,4-trichlorobenzene was also experimentally confirmed through identified 1,4-dichlorobenzene as its product.