磁赤铁矿/多羧基有机酸体系中五氯酚的异相光化学降解

Pentachlorophenol degradation in heterogeneous photo-maghemite-carboxylic acids system

自然界广泛存在的铁氧化物与多羧基有机酸在光照条件下能够由内源自身生成活性物过氧化氢,构成异相类Fenton体系降解污染物。在实验室构建了由磁赤铁矿和多羧基有机酸组成的光化学体系,研究了五氯酚在此体系中的降解和脱氯。结果表明,五氯酚在此异相光化学体系中的降解效率受波长范围、有机酸种类和氧气的显著影响。在UV-A波长范围,五氯酚具有较高的光降解效率。草酸能够显著促进五氯酚在磁赤铁矿中的异相光降解,但柠檬酸不具有此作用。氧气是体系中生成各种含氧活性物的必要条件。五氯酚在此体系中的降解遵循一级反应动力学。最佳实验条件下,五氯酚1h的降解率可达80%以上,脱氯率可达35%以上。对体系主要活性物过氧化氢的定量研究较好的解释了体系在各种条件下的活性差异。

In nature,iron oxides and carboxylic acids ubiquitously coexist in air,water surface and soil surface,in which a heterogeneous photo-Fenton-like reaction system can be set up to form H2O2 and ·OH that can oxidize almost all the organic compounds. The photodegradation of pentachlorophenol （PCP） in heterogeneous photo-maghemite-carboxylic acids system was investigated in this study under lab conditions. The efficiency of PCP degradation depended on the wavelength,the kind of carboxylic acids and the existence of oxygen. The high degradation rates could be obtained under UV-A rather than VIS. Oxalic acid largely promoted the rate of photodegradation and dechlorination of PCP while citric acid could not work like oxalic acid. Oxygen was necessary for the formation of active species （e.g. H2O2） and the degradation of PCP can be well described by the first-order kinetic model. After 1 h reaction time under optimum condition,the degradation ratio and the declorination ratio of PCP were above 80% and 35%,respectively. The quantitative study for the formation of H2O2 well explained the difference of the ability of system under different conditions.