State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China.
State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China.
Water Res. 2018 May 15;135:75-84. doi: 10.1016/j.watres.2018.02.014. Epub 2018 Feb 10.
This work investigated impacts of iodide (I) on the transformation of the widely used phenolic preservative methylparaben (MeP) as well as 11 other phenolic compounds by potassium permanganate (KMnO). It was found that KMnO showed a low reactivity towards MeP in the absence of I with apparent second-order rate constants (k) ranging from 0.065 ± 0.0071 to 1.0 ± 0.1 Ms over the pH range of 5-9. The presence of I remarkably enhanced the transformation rates of MeP by KMnO via the contribution of hypoiodous acid (HOI) in situ formed, which displayed several orders of magnitude higher reactivity towards MeP than KMnO. This enhancing effect of I was greatly influenced by solution conditions (e.g., I or KMnO concentration or pH), which could be well simulated by a kinetic model involving competition reactions (i.e., KMnO with I, KMnO with MeP, HOI with KMnO, and HOI with MeP). Similar enhancing effect of I on the transformation kinetics of 5 other selected phenols (i.e., p-hydroxybenzoic acid, phenol, and bromophenols) at pH 7 was also observed, but not in the cases of bisphenol A, triclosan, 4-n-nonylphenol, and cresols. This discrepancy could be well explained by the relative reactivity of KMnO towards phenols vs I. Liquid chromatography-tandem mass spectrometry analysis showed that iodinated aromatic products and/or iodinated quinone-like product were generated in the cases where I enhancing effect was observed. Evolution of iodinated aromatic products generated from MeP (10 μM) treated by KMnO (50-150 μM) in the presence of I (5-15 μM) suggested that higher I or moderate KMnO concentration or neutral pH promoted their formation. A similar enhancing effect of I (1 μM) on the transformation of MeP (1 μM) by KMnO (12.6 μM) and formation of iodinated aromatic products were also observed in natural water. This work demonstrates an important role of I in the transformation kinetics and product formation of phenolic compounds by KMnO, which has great implications for future applications of KMnO in treatment of I-containing water.
本研究考察了碘化物（I）对广泛使用的酚类防腐剂甲基对羟基苯甲酸酯（MeP）以及其他 11 种酚类化合物在高锰酸钾（KMnO）作用下转化的影响。结果表明，在不存在 I 的情况下，KMnO 与 MeP 的反应活性较低，表观二级速率常数（k）在 pH 值为 5-9 的范围内范围从 0.065±0.0071 到 1.0±0.1 Ms。I 的存在通过原位形成的次碘酸（HOI）显著提高了 KMnO 对 MeP 的转化速率，其对 MeP 的反应活性比 KMnO 高几个数量级。I 的这种增强作用受溶液条件（如 I 或 KMnO 浓度或 pH）的极大影响，可通过涉及竞争反应的动力学模型（即 KMnO 与 I、KMnO 与 MeP、HOI 与 KMnO 和 HOI 与 MeP）很好地模拟。在 pH 值为 7 时，也观察到 I 对 5 种其他选定酚类化合物（即对羟基苯甲酸、苯酚和溴酚类）转化动力学的类似增强作用，但在双酚 A、三氯生、4-壬基酚和甲酚的情况下则不然。这种差异可以通过 KMnO 对酚类化合物与 I 的相对反应活性很好地解释。液相色谱-串联质谱分析表明，在观察到 I 增强效应的情况下，生成了碘化芳香产物和/或碘化醌类产物。从 KMnO（50-150 μM）处理 MeP（10 μM）产生的碘化芳香产物的演变表明，较高的 I 或适中的 KMnO 浓度或中性 pH 促进了它们的形成。在天然水中也观察到 I（1 μM）对 KMnO（12.6 μM）转化 MeP（1 μM）和碘化芳香产物形成的类似增强作用。本研究证明了 I 在 KMnO 转化酚类化合物的动力学和产物形成中的重要作用，这对未来 KMnO 在含 I 水处理中的应用具有重要意义。
