不同UV工艺中阿特拉津的降解效果与机理研究

Degradation Effect and Mechanism of Atrazine in UV-based Oxidation Processes

在UV光照情况下,研究了反应条件对阿特拉津光氧化降解动力学和降解产物的影响,并分析了影响规律与作用机理。结果表明,阿特拉津的降解符合准一级反应动力学,其在单独UV工艺中的反应速率常数(k_(obs))为0. 049 6～0. 069 1 min^(-1),且阿特拉津初始浓度越低其去除率越高,溶液pH值对阿特拉津的降解速率无显著影响,这是由于不同溶液pH值条件下的摩尔吸光系数(ε)和量子产率(Φ)的差别较小导致的。在UV/H_2O_2工艺中,阿特拉津的降解速率随着H_2O_2投加量的增加呈现先增大后降低的趋势,当H_2O_2投加量为10 mg/L时,阿特拉津的光氧化降解速率最大;在不同H_2O_2投加量条件下,阿特拉津的降解速率均在中性条件下最大,碱性条件下次之,酸性条件下最小。在UV/TiO_2工艺中,阿特拉津的降解速率均低于单独UV工艺中的降解速率,且随着TiO_2投加量的增加呈现逐渐降低的趋势,此工艺中阿特拉津降解的最适pH值介于阿特拉津的p Ka与TiO_2的pH_(pzc)之间。此外,溶液pH值和工艺类型会显著影响阿特拉津光氧化降解产物的种类、生成量及变化趋势; H_2O_2和TiO_2投加量仅对阿特拉津产物的生成量存在影响,但未改变产物种类。

The effects of reaction conditions on degradation kinetics and degradation intennediates of atrazine ( ATZ ) under UV irradiation were investigated, and mechanism and interaction were analyzed. The results indicated that the photo-degradation rate of ATZ followed the pseudo-first-order degradation kinetics, and the reaction rate constant (kobs) was in the range of 0. 049 6-0. 069 1 min ^-1 in sole-UV process. Meanwhile, the ATZ removal rate decreased with the increase of initial ATZ concentration. There was no significant impact of pH on the photolysis rate of ATZ, which was mainly ascribed to the small difference of ε and Ф under different pH conditions. In UV/H2O2 process, the kahs of ATZ first increased then decreased with dosage of H2O2 increasing. When the dosage of H2O2 was 10 mg/L, the photo-degradation rate of ATZ was the highest. Under different H2O2 dosages, the degradation rates of ATZ were the highest under neutral conditions, followed by alkaline conditions and the lowest under acidic conditions. The A:obs in UV/TiO2 process was lower than those under the condition of sole-UV process and it gradually decreased with the dosage of TiO2 increasing. The optimal pH for the photo-degradation of ATZ was between the pKa of ATZ and the pHpzc of TiO2. In addition, the results showed that the pH and type of process significantly affected the species, production and variations of ATZ degradation products. The dosages of H2O2 and TiO2 only affected the production of ATZ products, but they did not change the product species.