超声波协同紫外光催化处理4-氯酚自由基作用机理

THE MECHANISM STUDIES ON SONOPHOTO-DEGRADATION OF 4CP BY FREE RADICAL

研究了超声波协同紫外光催化(US-UV)处理4-氯酚的去除效果,探讨了反应中自由基的作用机理。结果表明,超声波在紫外光催化反应中的协同效果明显,·OH的生成速率和4-氯酚的降解速率分别遵从0级和1级动力学方程,Cl-1生成速率不属于简单动力学方程。向溶液中投加羟基自由基清除剂可以大大抑制4-氯酚的降解;向溶液中投加氧化剂和金属离子可以清除溶液中的光生电子,提升4-氯酚的降解率,但体系中金属离子到达一定含量后,"短路"现象就会出现,4-氯酚的降解反应大大被削弱。试验还通过UV-Vis漫反射光谱发现TiO2和氯酚物质形成了化合物,并认为自由基首先是与这些表面化合物发生反应的。

A ultrasound assisted photocatalysis （US-UV） was used for photo-degradation of4-chlorophenol （4CP）,and the mechanism ofsonophoto-degradation of 4CP by free radical was studied. The results showed the synergistic effect was notable. ·OH radical production rate and 4 - chlorophenol degradation rate complied with zero - and first-order kinetic equation. Meanwhile Cl^-1 production rate did not comply with simple kinetic equation. Adding ·OH radical scavenger to the solution could inhibit the degradation of 4CP. Oxidants and metal ions in the solution could enhance the degradation rate of 4CP by scavenging the photogenerated electrons on the TiO2 surface, but when the concentrations of metal ions in the solution increased to a certain level, short-circuiting phenomenon emerged which reduced the degradation rate of 4CP greatly. Furthermore diffuse reflectance UV-Vis spectra indicated that surface complexes were formed and surface complexes were likely oxidized by free radicals at first.