Department of Environmental Science and Engineering, Nanjing Agricultural University, Nanjing, 210095, China.
Nanjing Institute of Environmental Science, Ministry of Environmental Protection of PR China, Nanjing, 210042, China.
Water Res. 2020 Sep 1;182:115970. doi: 10.1016/j.watres.2020.115970. Epub 2020 May 27.
Activated persulphate (PS) oxidation is a promising in situ remediation technology for groundwater and soils. Application of this technology to contaminated zones may result in a large quantity of PS residue in the subsurface environment due to inefficient activation and repeated injection. In this study, we demonstrated that natural organic matter (NOM) molecules could be reconfigured due to exposure to unactivated PS and bicarbonate, resulting in reduced disinfection byproducts formation potential in post chlorination process. Fourier transformed inferred spectrometry (FTIR), size exclusive chromotraghy (SEC), and mass spectrometry (MS) analysis revealed that hydroxylation and carboxylation of NOM occurred, followed by inter-molecular coupling via ether bonds. The change of both the reactivity toward free chlorine and molecular structure of NOM during PS/bicarbonate treatment was well mimicked by 3,5-dihydroxylbenzoic acid, suggesting that phenolic moieties in NOM molecules were the main sites underwent transformation in the PS/bicarbonate system. We propose that peroxymonocarbonate (HCO) formed upon the reaction between PS and bicarbonate was the main reactive species responsible for the reconfiguration of NOM. It selectively attacked the phenolic moieties via single-electron abstracting mechanism, leading to phenoxy radical intermediates which couple to each other via C-O-C bonds. The findings of this study shed light on the environmental behaviors and impacts of PS in groundwater environment.
过硫酸盐（PS）活化氧化是一种很有前途的地下水和土壤原位修复技术。由于活化效率低和重复注入，该技术在污染区的应用可能会导致地下环境中产生大量 PS 残留。在本研究中，我们证明了由于暴露于未活化的 PS 和碳酸氢盐，天然有机物（NOM）分子可能会重新配置，从而导致在后氯化过程中消毒副产物形成潜力降低。傅里叶变换推断光谱（FTIR）、尺寸排除色谱（SEC）和质谱（MS）分析表明，NOM 发生了羟化和羧化反应，随后通过醚键发生分子间偶联。在 PS/碳酸氢盐处理过程中，NOM 的反应性和分子结构的变化很好地被 3,5-二羟基苯甲酸模拟，这表明 NOM 分子中的酚基是在 PS/碳酸氢盐体系中发生转化的主要部位。我们提出，PS 与碳酸氢盐反应生成的过一碳酸盐（HCO）是导致 NOM 重新配置的主要反应性物质。它通过单电子提取机制选择性地攻击酚基，导致通过 C-O-C 键相互偶联的苯氧基自由基中间体。这项研究的结果揭示了 PS 在地下水环境中的环境行为和影响。
