共存物质对UV/PS降解莠灭净的影响及降解路径

Effect of coexisting substances on degradation of Ametryn in UV/persulfate process and possible reaction pathways

采用紫外(UV)激活过硫酸盐(PS)生成活性极强的自由基(·SO_4~–、·OH)降解莠灭净(AMT),考察了UV/PS工艺对AMT降解效果及反应动力学模型。研究了水中不同浓度的无机阴离子(Cl~–、HCO_3~–、NO_3~–)、天然有机质(腐植酸)对反应效果及速率的影响,比较了超纯水、自来水和锡东水厂不同工艺出水作为不同水质背景时AMT的去除效率,并推测了UV/PS降解AMT的降解产物及可能的降解路径。结果表明:UV/PS对AMT的降解符合准一级反应动力学模型(R^2≥0.94)。水中Cl~–浓度为5mmol/L时,会抑制AMT的降解,而其他浓度的Cl~–对反应的影响并不明显;随着HCO_3~–浓度的增加,准一级反应速率常数kobs逐渐减小;NO_3~–会加快AMT的去除,当其浓度为200mmol/L时对AMT降解的促进作用变弱;随着腐植酸质量浓度的增加,kobs逐渐减小。AMT在超纯水中的降解率高于其他实际水体中的降解率。UV/PS系统降解AMT过程中主要的降解产物可能是2-甲硫基-4,6-二氨基-1,3,5-三嗪和2-羟基-4-乙氨基-6-异丙氨基-1,3,5-三嗪。

The degradation of Ametryn（AMT）was evaluated by UV activated persulfate（PS）.The degradation process was based on generation of sulfate radical（·SO4^-）,hydroxyl radical（·OH）.The effectiveness and the reaction kinetics model of the UV/PS process in the degradation of AMT was investigated. Effects of different concentrations of inorganic anions（Cl^–,HCO3^-,NO3^-）,natural organic matter（humic acid）in aqueous solution for the effectiveness and the kinetics of AMT degradation was studied,while emphasis was given on the degradation of AMT in ultrapure water,tap water,effluent water of different process in Xi Dong Water Plant as the solution backgrounds,and the possible degradation products and pathways of AMT were proposed.The results showed that the degradation of AMT in UV/PS would follow the first-order reaction kinetics model（R-2≥0.94）. When Cl^– concentration was 5mmol/L,the decomposition of AMT would be inhibited,while the influence of other Cl^–concentration were ignored. kobs decreased with the increase of HCO3^-,NO3^- would speed up the removal of AMT,when NO3^- concentration was 200mmol/L,the increasing extent was weakened. kobs decreased with the increase of humic acid.The degradation rate of AMT in ultrapure water was highest among different water matrices.The major degradation products in this study are 2-methylthio-4,6-diamino-1,3,5-triazine,2-hydroxy-4-ethylamino-6-isopropylamino-1,3,5-triazine.