State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
J Hazard Mater. 2011 Jan 30;185(2-3):1256-63. doi: 10.1016/j.jhazmat.2010.10.040. Epub 2010 Oct 16.
The photodegradation of three antibiotics, oxytetracycline (OTC), doxycycline (DTC), and ciprofloxacin (CIP) in UV and UV/H(2)O(2) process was investigated with a low-pressure UV lamp system. Experiments were performed in buffered ultrapure water (UW), local surface water (SW), and treated water from local municipal drinking water treatment plant (DW) and wastewater treatment plant (WW). The efficiency of UV/H(2)O(2) process was affected by water quality. For all of the three selected antibiotics, the fastest degradation was observed in DW, and the slowest degradation occurred in WW. This phenomenon can be explained by R(OH,UV), defined as the experimentally determined OH radical exposure per UV fluence. The R(OH,UV) values represent the background OH radical scavenging in water matrix, obtained by the degradation of para-chlorobenzoic acid (pCBA), a probe compound. In natural water, the indirect degradation of CIP did not significantly increase with the addition of H(2)O(2) due to its effective degradation by UV direct photolysis. Moreover, the formation of several photoproducts and oxidation products of antibiotics in UV/H(2)O(2) process was identified using GC-MS. Toxicity assessed by Vibrio fischer (V. fischer), was increased in UV photolysis, for the photoproducts still preserving the characteristic structure of the parent compounds. While in UV/H(2)O(2) process, toxicity increased first, and then decreased; nontoxic products were formed by the oxidation of OH radical. In this process, detoxification was much easier than mineralization for the tested antibiotics, and the optimal time for the degradation of pollutants in UV/H(2)O(2) process would be determined by parent compound degradation and toxicity changes.
采用低压紫外灯系统研究了三种抗生素（土霉素、强力霉素和环丙沙星）在 UV 和 UV/H2O2工艺中的光降解情况。实验在缓冲超纯水（UW）、当地地表水（SW）以及当地市政饮用水处理厂（DW）和废水处理厂（WW）处理后的水中进行。UV/H2O2工艺的效率受到水质的影响。对于所选的三种抗生素，在 DW 中观察到最快的降解，而在 WW 中降解最慢。这种现象可以用 R（OH，UV）来解释，R（OH，UV）定义为每单位紫外线辐照度下实际测定的羟基自由基暴露量。R（OH，UV）值代表水基质中背景羟基自由基的清除，通过对探针化合物对氯苯甲酸（pCBA）的降解来获得。在天然水中，由于 CIP 可通过 UV 直接光解有效降解，因此间接降解不会因添加 H2O2而显著增加。此外，采用 GC-MS 鉴定了抗生素在 UV/H2O2工艺中的光产物和氧化产物。通过发光杆菌（V. fischer）评估的毒性在 UV 光解中增加，因为光产物仍保留母体化合物的特征结构。而在 UV/H2O2工艺中，毒性先增加后降低；羟基自由基氧化生成无毒产物。在该过程中，与矿化相比，对于测试的抗生素，解毒更容易，并且在 UV/H2O2工艺中污染物降解的最佳时间将由母体化合物降解和毒性变化来确定。
