EPR Evidence for Mechanistic Diversity of Cu(II)/Peroxygen Oxidation Systems by Tracing the Origin of DMPO Spin Adducts,Environmental Science & Technology

当前位置： X-MOL 学术 › Environ. Sci. Technol. › 论文详情

Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)

EPR Evidence for Mechanistic Diversity of Cu(II)/Peroxygen Oxidation Systems by Tracing the Origin of DMPO Spin Adducts
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2022-05-24 , DOI: 10.1021/acs.est.2c00459
Lingli Wang ₁ , Yu Fu ₁ , Qingchao Li ₁ , Zhaohui Wang _{1,

2,

3,

4}

Affiliation

Electron paramagnetic resonance (EPR) has been extensively used for the identification of free radicals that are generated from advanced oxidation processes (AOPs) so as to establish the reaction mechanism. However, some misinterpretations or controversies on the identity of detected EPR signals remain in the literature. This study, with Cu(II)-based AOPs as examples, comprehensively investigated the origin of 5,5-dimethyl-l-pyrroline N-oxide (DMPO) adducts in Cu(II) alone, Cu(II)/H₂O₂, Cu(II)/peroxymonosulfate (PMS), and Cu(II)/peroxydisulfate (PDS) systems. In most Cu(II) systems, DMPO-OH signals can be detected even without any peroxygens, indicating the presence of other origins of this adduct in addition to the genuine spin trapping of ^•OH by DMPO. According to the formed secondary radical adducts (DMPO-OCH₃ from a nonradical process or DMPO-CH₂OH from a radical oxidation) derived from methanol quenching, we propose that CuO⁺, instead of free radicals, is involved in the Cu(II)/PMS system, while ^•OH is indeed generated in the Cu(II)/H₂O₂ and Cu(II)/PDS systems under neutral conditions. Notably, ¹⁷O-incorporation experiments demonstrate that −OH in the detected DMPO-OH adduct originates 100% from water in the Cu(II) alone system but the amount of −OH is over 99.8% from the oxidant while peroxygens are added. In addition, DMPO-O₂^– appears only in the Cu(II)/PDS system under highly alkaline conditions and H₂O is not involved in superoxide formation.

中文翻译：

通过追踪 DMPO 自旋加合物的来源，证明 Cu(II)/过氧氧化系统的机械多样性的 EPR 证据

电子顺磁共振（EPR）已被广泛用于识别高级氧化过程（AOP）产生的自由基，从而建立反应机理。然而，文献中仍然存在对检测到的 EPR 信号身份的一些误解或争议。本研究以Cu(II)基AOPs为例，全面研究了Cu(II)单独、Cu(II)/H ₂ O中5,5-二甲基-l-吡咯啉N-氧化物(DMPO)加合物的来源。 ₂、Cu(II)/过氧单硫酸盐(PMS)和Cu(II)/过氧二硫酸盐(PDS)体系。在大多数 Cu(II) 系统中，即使没有任何过氧化物也可以检测到 DMPO-OH 信号，这表明除了真正的自旋捕获之外，该加合物还存在其他来源^。哦，DMPO。根据甲醇猝灭形成的二次自由基加合物（非自由基过程的 DMPO-OCH ₃或自由基氧化的 DMPO-CH ₂ OH），我们提出 CuO ⁺而非自由基参与了 Cu(II )/PMS 体系，而在中性条件下，Cu(II)/H ₂^O₂和 Cu(II)/PDS 体系中确实会产生 OH 。值得注意的是，^{17 个}O 掺入实验表明，检测到的 DMPO-OH 加合物中的 -OH 100% 来源于单独的 Cu(II) 体系中的水，但在添加过氧化物时 -OH 的量超过 99.8% 来自氧化剂。此外，DMPO-O ₂^–仅在高碱性条件下的 Cu(II)/PDS 体系中出现，H ₂ O 不参与超氧化物的形成。

更新日期：2022-05-24

点击分享查看原文

点击收藏

阅读更多本刊新发论文本刊介绍/投稿指南