水中腐殖酸对阿特拉津光敏降解的影响机理分析

RESEARCH ON INFLUENCE MECHANISM OF HUMIC ACID IN WATER TO ATRAZINE PHOTOSENSITIVE DEGRADATION

腐殖酸是天然水体中重要的光敏剂,能够促进持久性有机物的自然光敏降解。常用除草剂阿特拉津在农田使用后会随地表径流进入水体成为难降解有机污染物。探讨了在可见光照射下,水中腐殖酸光敏降解阿特拉津的反应动力学和降解机理。通过自由基探针实验和氮饱和淬灭氧实验,分别对可见光反应体系中受光能激发产生的活性物种~1O_2、·OH和~3HA~*进行了定量分析。结果表明:水中腐殖酸光敏降解阿特拉津的过程符合一级反应动力学,其速率常数为0.4454 h^(-1);作用于阿特拉津的·OH、~1O_2浓度分别为2.46×10^(-16),5.70×10^(-14) mol/L,~3HA~*对其光降解也具有一定的促进作用,且活性物种对阿特拉津的降解作用为·OH>~1O_2>~3HA~*。·OH氧化作用主要发生于阿特拉津的脱烷基化反应,~3HA~*则更容易与乙基反应。

Humic acid is a significant kind of photosensitizer in natural water,which will promote the natural photosensitive degradation of persistent organic matters.Atrazine,a common herbicide,has flowed into the water body with surface runoff as a degradation-resistant organic pollutant .after farmland use.In this paper,we investigated the photosensitive degradation kinetics and degradation mechanism of atrazine by humic acid in water under the visible light.The free radical probe experiments and nitrogen.saturation quenching oxygen experiments were conducted to quantitatively analyzing reactive species (1O2,.OH and 3HA^*)generated in the visible light reaction system under light.The results showed that the photosensitive degradation of atrazine by humic acid in water obeyed the first order reaction kinetics,and its rate constant was 0.4454h^-1 ; the concentrations of .OH and 1O2to atrazine were 2.46×10^-16mol/L and 5.70×10^-14mol/L,respectively,and 3HA^*had a certain promotion effect on its photosensitive degradation,where the effect of above reactive species on atrazine degradation process could be sorted as the following order:.OH >1O2>3HA^*.The oxidation of .OH mainly occurred in the dealkylation reaction of atrazine,and 3HA^*was more inclined to react with ethyl.