Department of Environmental Science and Engineering, Nanjing Agricultural University, Nanjing 210095, China.
Department of Environmental Science and Engineering, Nanjing Agricultural University, Nanjing 210095, China.
Water Res. 2017 Jun 1;116:324-331. doi: 10.1016/j.watres.2017.03.043. Epub 2017 Mar 22.
Persulfate (PS) is widely used as an oxidant for in situ chemical remediation of contaminated groundwater. In this study we demonstrated for the first time that PS could be activated by bicarbonate. Acetaminophen was used as the probe compound to examine the reactivity of PS/bicarbonate system. It was found that acetaminophen could be effectively transformed and the reaction rate appeared pseudo-first-order to the concentrations of both acetaminophen and PS. Radical scavenger tests indicated that neither free radicals (SO and HO) nor superoxide (O) was responsible for acetaminophen transformation. Generation of singlet oxygen (O) was verified using furfuryl alcohol (FFA) as a probe. Formation of O was further quantified in DO fortified solution based on kinetic solvent isotopic effect (KSIE) but it was found that O contributed only 51.4% of the total FFA transformation. The other 48.6% was presumed to be ascribed to the reaction with peroxymonocarbonate (HCO). However, the transformation of acetaminophen was mostly due to the reaction with HCO but not O. Instead of degradation, HCO oxidized acetaminophen via a one-electron abstraction mechanism resulting in the generation of acetaminophen radicals which coupled to each other to form dimers and trimers. HCO also hydrolyzed rapidly to form hydrogen peroxide (HO) which led to the formation of O, during which O was a key intermediates. Because bicarbonate is ubiquitously presented in groundwater, the findings of this research provide important insights into the fundamental processes involved in PS oxidation in subsurface.
过硫酸盐（PS）被广泛用作原位化学修复受污染地下水的氧化剂。在本研究中，我们首次证明了过硫酸盐可以被碳酸氢盐激活。我们使用对乙酰氨基酚作为探针化合物来考察 PS/碳酸氢盐体系的反应活性。结果发现，对乙酰氨基酚可以被有效地转化，且反应速率对 PS 和对乙酰氨基酚的浓度均呈现准一级动力学关系。自由基捕获实验表明，对乙酰氨基酚的转化既不是由自由基（SO 和 HO），也不是由超氧自由基（O）引起的。使用糠基醇（FFA）作为探针验证了 singlet oxygen（O）的生成。根据动力学溶剂同位素效应（KSIE），在 DO 强化溶液中进一步定量生成的 O，但发现 O 仅贡献了 FFA 总转化的 51.4%。其余的 48.6% 被认为归因于与过一碳酸盐（HCO）的反应。然而，对乙酰氨基酚的转化主要是由于与 HCO 的反应而不是 O。HCO 通过单电子抽取机制氧化对乙酰氨基酚，生成对乙酰氨基酚自由基，这些自由基相互偶联形成二聚体和三聚体，而不是降解。HCO 也迅速水解形成过氧化氢（HO），导致 O 的形成，其中 O 是关键中间体。由于碳酸氢盐在地下水中普遍存在，因此本研究的结果为 PS 在地下环境中的氧化过程提供了重要的见解。
