Kinetic models and pathways of ronidazole degradation by chlorination, UV irradiation and UV/chlorine processes.
Kinetic models and pathways of ronidazole degradation by chlorination, UV irradiation and UV/chlorine processes.
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DOI：
10.1016/j.watres.2014.07.041
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发表时间：
2014-11
期刊：
影响因子：
12.8
通讯作者：
Lang Qin;Yi-Li Lin;Bin Xu;Chen-yan Hu;Fu-xiang Tian;Tian-Yang Zhang;Wen-Qian Zhu;He Huang;
中科院分区：
文献类型：
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作者：
Lang Qin;Yi-Li Lin;Bin Xu;Chen-yan Hu;Fu-xiang Tian;Tian-Yang Zhang;Wen-Qian Zhu;He Huang;
本文研究了氯化(Cl2)、紫外光照射和UV/氯联合工艺降解硝唑(RNZ)的动力学和途径。RNZ的氯化降解动力学符合二级动力学，酸催化反应的速率常数分别为(2.13±0.15)×102M−2S−1、(0.82M±0.52)×102M−2M−1S−1和(2.06±0.09)×1010−1M−1S−1。虽然紫外光对RNZ的降解比氯化更有效，但RNZ在254 nm处的量子产率很低，仅为1.02×10~(-10)−~(-3)·−~(-1)。在UV/氯过程中，RNZ由于产生羟基自由基而被有效降解和矿化。测得RNZ与羟基自由基间的二级反应速率常数为(2.92±0.05)×109M−1S−1。用超高效液相色谱-电喷雾电离-质谱法对RNZ在三个过程中的降解中间体进行了鉴定，并提出了降解途径。此外，还进一步考察了三种工艺对氯苦苦苷(TCNM)和氯仿(CF)生成的影响。在饮用水处理中，增强UV/ClO过程中CF和TCNM前体的形成值得广泛关注。
Degradation kinetics and pathways of ronidazole (RNZ) by chlorination (Cl2), UV irradiation and combined UV/chlorine processes were investigated in this paper. The degradation kinetics of RNZ chlorination followed a second-order behavior with the rate constants calculated as (2.13 ± 0.15) × 102M−2s−1, (0.82 ± 0.52) × 10−2M−1s−1and (2.06 ± 0.09) × 10−1M−1s−1for the acid-catalyzed reaction, as well as the reactions of RNZ with HOCl and OCl−, respectively. Although UV irradiation degraded RNZ more effectively than chlorination did, very low quantum yield of RNZ at 254 nm was obtained as 1.02 × 10−3mol E−1. RNZ could be efficiently degraded and mineralized in the UV/chlorine process due to the generation of hydroxyl radicals. The second-order rate constant between RNZ and hydroxyl radical was determined as (2.92 ± 0.05) × 109M−1s−1. The degradation intermediates of RNZ during the three processes were identified with Ultra Performance Liquid Chromatography – Electrospray Ionization - mass spectrometry and the degradation pathways were then proposed. Moreover, the variation of chloropicrin (TCNM) and chloroform (CF) formation after the three processes were further evaluated. Enhanced formation of CF and TCNM precursors during UV/chlorine process deserves extensive attention in drinking water treatment.