Abstract:

The degradation of gemfibrozil (GEM) by UV/H₂O₂ and UV/NaClO processes was comparatively evaluated. Both advanced oxidation systems can effectively degrade GEM. Compared with UV/H₂O₂ system, the degradation rate of GEM in UV/NaClO system was faster. In UV/H₂O₂ and UV/NaClO systems, the degradation rate of the target increased with the increase of oxidant concentrations. Because pH could affect the oxidation capacity of ‧OH and the composition ratio of free radicals in UV/NaClO system, the pH of the solutions had a significant impact on both systems. When pH was increased from 5 to 11, the kobs in UV/H₂O₂ and UV/NaClO decreased from 0.2115min^-1 and 1.3115min^-1 to 0.1064min^-1 and 0.2283min^-1, respectively. Cl^- and HCO{}_{\mathrm{3}}^{-} can slightly accelerate the degradation of GEM in UV/NaClO system, but slightly slow down the degradation of GEM in UV/H₂O₂ system. HA can inhibit GEM degradation in both systems through competition and filter effect. Because the molar absorption coefficient of HClO/ClO^- was higher than H₂O₂, HA had less inhibitory effect on GEM degradation in UV/NaClO system compared with UV/H₂O₂ system. The main oxidation species degrading GEM in UV/NaClO system were ‧OH and Cl‧. The degradation path of GEM in both systems mainly included hydroxylation, demethylation, H-extraction and C—O bond breakage steps. In terms of economic benefits, UV/NaClO system was more cost-effective than UV/H₂O₂ system.

Key words: radical, UV/H₂O₂, UV/NaClO, advanced oxidation, degradation path, reaction kinetics

摘要：

对比了吉非罗齐（GEM）在UV/H₂O₂和UV/NaClO系统中的降解，两个高级氧化系统均可以有效降解GEM，与UV/H₂O₂相比，UV/NaClO对GEM的去除速率更快。在UV/H₂O₂和UV/NaClO系统内，目标物的降解速率随着氧化剂浓度的增加而加快，由于pH会影响‧OH的氧化能力和UV/NaClO系统内自由基的组成比例，因此溶液的pH对两个系统均有显著的影响，当溶液pH从5增加到11时，GEM在UV/H₂O₂系统和UV/NaClO系统内的k_obs分别从0.2115min^-1和1.3115min^-1降低到0.1064min^-1和0.2283min^-1。Cl^-和HCO{}_{\mathrm{3}}^{-}可以稍微加快GEM在UV/NaClO系统内的降解速率，却减慢了GEM在UV/H₂O₂系统内的降解速率；HA可以通过竞争效应和滤光效应抑制GEM在两个系统内的降解，但由于HClO/ClO^-的摩尔吸光系数高于H₂O₂，HA对GEM在UV/NaClO系统内降解的抑制效应较小。‧OH和Cl‧是UV/NaClO系统内降解GEM的主要氧化物种，GEM在两个高级氧化系统内降解过程主要包括羟基化、去甲基化、H提取和C—O键断裂步骤。经济效益评估可知，UV/NaClO系统比UV/H₂O₂系统更具有成本效益。

关键词: 自由基, 紫外/过氧化氢, 紫外/次氯酸钠, 高级氧化, 降解路径, 反应动力学