Mechanism and Kinetic Analysis on Degradation of Atrazine by UV/PS
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摘要: 为了解决阿特拉津（atrazine，ATZ）对水体污染问题，采用紫外/过二硫酸盐 （ultraviolet/peroxodisulfate，UV/PS） 降解水体中的ATZ，考察了不同pH值、UV强度、PS浓度、温度条件下UV/PS对ATZ的降解效果，同时对其降解机理、降解动力学及降解路径进行了探讨. 机理分析表明，UV可使ATZ发生光解，UV/PS能快速降解水体中ATZ，中性偏碱性条件下UV/PS体系中同时存在SO4−• 和 •OH. 动力学分析表明，不同温度、pH值、PS浓度、UV强度条件下UV/PS降解ATZ动力学符合准一级反应动力学. 降解路径分析表明，ATZ主要通过脱氯、加羟基、脱乙基、脱异丙基等方式被降解，几种降解方式并不孤立，但三嗪环并未开环降解. 试验结果表明，反应体系温度为25 ℃，PS浓度为70 μmol/L，UV强度为50 mW/cm2，反应体系初始pH为5.8，反应时间为20 min时，UV/PS体系对2.5 μmol/L ATZ的降解率可达91.03%.Abstract: In order to deal with water pollution caused by atrazine (ATZ), the effects, mechanism, kinetics and pathway of ATZ degradation by ultraviolet/peroxodisulfate (UV/PS) were explored in terms of pH, UV intensity, PS concentration and temperature. The analysis of degradation mechanism indicates that UV could be photolyzed by UV and rapidly degraded by UV/PS in water. SO4−• and •OH coexisted in UV/PS system under neutral and weakly alkaline conditions. Kinetic analysis show that UV/PS degradation of ATZ fitted to quasi first-order reaction kinetics with differing temperature, pH, PS concentration and UV intensity. Degradation pathway analysis suggest that the main degradation pathways of ATZ were dechlorination, hydroxylation, deethylation and deisopropyl, all of which were correlated; yet the triazine ring was notoxidized and opened. The results show that the degradation rate of 2.5 μmol/L ATZ by UV/PS system was 91.03% when the system temperature, PS concentration, UV intensity, initial pH value and response time was 25 ℃, 70 μmol/L, 50 mW/cm2, 5.8 and 20 min, respectively.
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Key words:
- ultraviolet /
- peroxodisulfate /
- free radicals /
- atrazine /
- degradation mechanism /
- kinetics /
- degradation pathway
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图 3 PS浓度对ATZ降解效果的影响
Figure 3. Effect of PS concentration on ATZ degradation efficiency
图 5 UV/PS体系中各组分氧化效果分析及乙醇对UV/PS降解ATZ的影响
Figure 5. Analysis on oxidation effect of each component in UV/PS system and effect of ETA on degradation of ATZ by UV/PS
图 6 UV/PS降解ATZ可能降解路径
注：（1）—去C-N键断裂； （2）—羟基化； （3）—脱水反应.
Figure 6. Possible degradation pathways of ATZ by UV/PS
表 1 不同反应条件下UV/PS降解ATZ反应动力学拟合参数
Table 1. Fitted kinetics parameters of UV/PS degradation ATZ in different reaction conditions
反应条件 速率常数/min−1 R2 动力学方程 pH 3.0 0.360 6 0.972 3 $\ln \left( {C/{C_0}} \right) = - 0.360\;6t + 0.240\;6$ 4.0 0.290 6 0.956 8 $\ln \left( {C/{C_0}} \right) = - 0.290\;6t + 0.144\;5$ 7.0 0.381 9 0.997 9 $\ln \left( {C/{C_0}} \right) = - 0.381\;9t - 0.021\;6$ 8.0 0.270 5 0.995 0 $\ln \left( {C/{C_0}} \right) = - 0.207\;5t + 0.067\;1$ 9.0 0.283 6 0.994 6 $\ln \left( {C/{C_0}} \right) = - 0.283\;6t + 0.059\;5$ UV强度/（mW•cm−2） 30 0.004 9 0.912 2 $\ln \left( {C/{C_0}} \right) = - 0.004\;9t - 0.026\;6$ 50 0.044 1 0.997 7 $\ln \left( {C/{C_0}} \right) = - 0.044\;1t - 0.010\;8$ 100 0.070 9 0.998 5 $\ln \left( {C/{C_0}} \right) = - 0.070\;9t - 0.009\;8$ PS浓度/（μmol•L−1） 10 0.022 9 0.977 7 $\ln \left( {C/{C_0}} \right) = - 0.022\;9t + 0.013\;2$ 20 0.035 0 0.982 7 $\ln \left( {C/{C_0}} \right) = - 0.035\;0t - 0.041\;3$ 30 0.044 1 0.997 7 $\ln \left( {C/{C_0}} \right) = - 0.044\;1t - 0.010\;8$ 40 0.055 3 0.978 3 $\ln \left( {C/{C_0}} \right) = - 0.055\;3t - 0.009\;8$ 50 0.074 2 0.992 0 $\ln \left( {C/{C_0}} \right) = - 0.074\;2t - 0.074\;4$ 60 0.092 2 0.989 9 $\ln \left( {C/{C_0}} \right) = - 0.092\;2t - 0.058\;4$ 70 0.116 9 0.984 5 $\ln \left( {C/{C_0}} \right) = - 0.116\;9t + 0.057\;1$ 温度/℃ 10 0.032 4 0.971 5 $\ln \left( {C/{C_0}} \right) = - 0.032\;4t - 0.082\;9$ 15 0.053 8 0.987 7 $\ln \left( {C/{C_0}} \right) = - 0.053\;8t - 0.055\;8$ 20 0.074 2 0.992 0 $\ln \left( {C/{C_0}} \right) = - 0.074\;2t - 0.074\;4$ 25 0.122 8 0.992 2 $\ln \left( {C/{C_0}} \right) = - 0.122\;8t - 0.011\;1$ 
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