Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu 210023, China.
Water Res. 2021 Apr 1;193:116904. doi: 10.1016/j.watres.2021.116904. Epub 2021 Feb 4.
Mineral-humic complexes, known as mineral-associated organic matter (MAOM), are ubiquitous in natural waters. However, the interaction between organic pollutants and MAOM remains elusive, which may affect their degradation process. In this study, photochemical transformation of chlorophene (CP) in the presence of MAOM, prepared by coating aluminum hydroxide with humic acid (HA-HAO), was investigated. Our results showed that the degradation of CP was significantly enhanced in the presence of HA-HAO, and the degradation rate constant was ~5 times as that with HA only. It was because the adsorption of CP to HA-HAO particles was greatly enhanced, and concentration of reactive oxygen species (ROS) was increased on HA-HAO surfaces, which further promoted the reactions between CP and ROS. The quenching experiments combined with EPR technology confirmed that superoxide anion (O) was the primary reactive radical on CP photodegradation. More importantly, the degradation of CP with HA-HAO followed a hydroxylation process, rather than the oligomerization reaction with HA only. Spectroscopic analysis provided direct evidence for the formation of hydrogen bonding between CP phenolic hydroxyl group and surface oxygen of HAO, which would suppress the reactivity of phenolic hydroxyl group, consequently the ortho- and meta-positions of CP became more facile for the hydroxylation reaction. This study shows the importance of MAOM in altering the photochemical behavior and transformation pathway of organic contaminants.
矿物-腐殖质复合物，又称矿物结合有机物（MAOM），在天然水中普遍存在。然而，有机污染物与 MAOM 之间的相互作用仍然难以捉摸，这可能会影响它们的降解过程。在本研究中，研究了在 MAOM（通过将腐殖酸（HA）涂覆在氢氧化铝上制备）存在下，五氯酚（CP）的光化学转化。结果表明，在 HA-HAO 存在下，CP 的降解明显增强，降解速率常数约为只有 HA 时的 5 倍。这是因为 CP 对 HA-HAO 颗粒的吸附大大增强，并且在 HA-HAO 表面上增加了活性氧物种（ROS）的浓度，这进一步促进了 CP 与 ROS 之间的反应。猝灭实验结合 EPR 技术证实，超氧阴离子（O）是 CP 光降解的主要活性自由基。更重要的是，CP 与 HA-HAO 的降解遵循羟化过程，而不是仅与 HA 的聚合反应。光谱分析为 CP 酚羟基与 HAO 表面氧之间形成氢键提供了直接证据，这会抑制酚羟基的反应性，从而使 CP 的邻位和间位更容易发生羟化反应。这项研究表明 MAOM 在改变有机污染物的光化学行为和转化途径方面的重要性。
