紫外/氯降解普里米酮的效能和机理

选用普里米酮(primidone, PRM)为目标污染物，研究了紫外/氯高级氧化工艺对PRM的降解效能及反应机理，分别考察了pH、水体常见阴离子(Cl⁻、${{\rm{HCO}}_3^{-} }$和${{\rm{NO}}_3^{-} }$)和出水有机物(effluent organic matter, EfOM)对PRM降解效果的影响，并研究了PRM在类Fenton体系中的削减情况；同时，根据溶液总有机碳(TOC)的矿化、芳香性中间产物和小分子有机酸的生成，阐明了在紫外/氯体系中PRM的降解机理。结果表明，当PRM初始浓度为5 μmol·L⁻¹、自由氯浓度为70 μmol·L⁻¹、溶液pH为7时，反应10 min后，PRM的去除率为84%，ClO·对PRM的削减起主导作用，其次为·OH，而Cl₂⁻·对PRM无氧化作用。当pH为6.2时污染物降解效果最佳。在一定范围内，Cl⁻几乎不影响PRM的降解，${{\rm{HCO}}_3^{-} }$因捕获自由基表现为抑制作用，${{\rm{NO}}_3^{-} }$因光解产生更多·OH进而加快PRM的分解。当Fe³⁺浓度为50 μmol·L⁻¹时，PRM降解速率达到最大值0.84 min⁻¹。2种EfOM的引入对PRM降解产生抑制作用，且憎水性EfOM的抑制作用更加显著。TOC矿化实验和降解路径分析结果表明，紫外/氯体系对PRM有一定的矿化作用且PRM首先通过连续的羟基化作用转化为苯甲酸等物质，同时母体化合物和中间体还可继续被氧化为小分子有机酸。PRM中的氮元素最终以${{\rm{NO}}_2^{-} }$和${{\rm{NH}}_4^{+} }$的形式存在，且在各种活性自由基的作用下${{\rm{NH}}_4^{+} }$可转化为${{\rm{NO}}_2^{-} }$。

Degradation efficiency and mechanism of primidone by UV/chorine process

Primidone (PRM) was selected as target contaminant in this study, and the degradation efficiency and reaction mechanism of PRM in UV/chlorine advanced oxidation process were investigated. The effects of solution pH, common anions (Cl−, ${\rm{HCO}}_3^{-} $ and ${\rm{NO}}_2^{-} $) and effluent organic matter (EfOM) on the degradation of PRM were studied, respectively. PRM decay in Fenton-like system was also studied. Meanwhile, the degradation mechanism of PRM in UV/chlorine system was identified based on TOC mineralization, the formation of aromatic intermediate products and small molecular acid. The results showed that when the initial concentrations of PRM and free chlorine were 5 μmol·L−1 and 70 μmol·L−1, respectively, and solution pH was 7, PRM removal rate was 84% in 10 min. ClO· played a leading role in PRM degradation, followed by ·OH, while Cl2−· did not participate in the conversion process. When solution pH was 6.2, the best degradation effect of pollutant occurred. The PRM degradation was almost unaffected by Cl− within a certain range, and it was inhibited by ${\rm{HCO}}_3^{-} $ due to the radical scavenger, while the introduction of ${\rm{NO}}_3^{-} $ greatly promoted PRM degradation because of the formation of additional •OH vis photolysis of ${\rm{NO}}_2^{-} $. When the Fe3+ concentration was 50 μmol·L−1, the PRM degradation rate reached the maximum value of 0.84 min−1. The introduction of two kinds of EfOM could inhibit the PRM degradation, and the hydrophobic EfOM played a more significant role. TOC mineralization experiment and degradation path analysis showed that UV/chlorine AOP had a certain mineralization effect on PRM, which first converted to benzoic acid and other substances through continuous hydroxylation, and the precursor and intermediates could continue to be oxidized into small molecular organic acids. It was found that the nitrogen elements in PRM molecular eventually existed in the form of ${\rm{NO}}_2^{-} $ and ${\rm{NH}}_4^{+} $, and ${\rm{NH}}_4^{+} $ could transform into ${\rm{NO}}_2^{-} $ under the attack of various active radicals.