Key Laboratory of Soil Environment and Pollution Remediation Institute of Soil Science, CAS, Nanjing, Jiangsu Province, 210008, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
Key Laboratory of Soil Environment and Pollution Remediation Institute of Soil Science, CAS, Nanjing, Jiangsu Province, 210008, China.
J Hazard Mater. 2018 Sep 5;357:483-490. doi: 10.1016/j.jhazmat.2018.06.030. Epub 2018 Jun 22.
The natural formation of hydroxyl radicals (OH) is important for the attenuation of organic contaminants. In this study, seven model polyphenols were selected to react with four types of smectite clays with varied Fe contents in the presence of HO. Diethyl phthalate (DEP) was selected as a model organic contaminant due to its wide distribution in environment. The results show the appearance of Fe-bearing smectite clays can significantly promote ·OH formation with polyphenols and HO under anoxic conditions; clay particle size, the content and location of lattice Fe in smectite clays greatly affect OH formation. Hydrogen bond between phenolic group and smectite surfaces, and cation assisted hydrogen bond between carboxylic group and clay surfaces are important types of complexation. Electrons can be transferred from coordinated polyphenols to structural Fe(III) atoms in tetrahedral layers or at broken edges to form structural Fe(II) and/or semiquinone radicals, both of which can induce HO decomposition to OH. DEP can be degraded by OH attack, and the main products are proposed as phthalic acid, monomethyl phthalate, hydroxyl-diethyl phthalates. Our findings suggest that Fe(III)-bearing smectite clay can be reduced by polyphenol and produce OH in anoxic environments, which can induce organic contaminants transformation.
羟基自由基（OH）的自然形成对于有机污染物的衰减很重要。在这项研究中，选择了七种模型多酚，在 HO 的存在下，与四种具有不同 Fe 含量的蒙脱石粘土反应。邻苯二甲酸二乙酯（DEP）被选为模型有机污染物，因为它在环境中广泛分布。结果表明，含 Fe 的蒙脱石粘土的出现可以显著促进多酚和 HO 在缺氧条件下形成·OH；粘土粒径、蒙脱石粘土晶格 Fe 的含量和位置极大地影响 OH 的形成。酚基团与蒙脱石表面之间的氢键，以及羧酸基团与粘土表面之间的阳离子辅助氢键是重要的络合类型。电子可以从配位多酚转移到四面体层或破裂边缘的结构 Fe（III）原子上，形成结构 Fe（II）和/或半醌自由基，这两者都可以诱导 HO 分解为 OH。OH 攻击可以降解 DEP，提出的主要产物为邻苯二甲酸、单甲基邻苯二甲酸、二羟乙基邻苯二甲酸酯。我们的研究结果表明，在缺氧环境中，多酚可以还原含 Fe（III）的蒙脱石粘土并产生 OH，这可以诱导有机污染物的转化。
