Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu, 611756, China.
Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu, 611756, China.
Chemosphere. 2022 Nov;306:135506. doi: 10.1016/j.chemosphere.2022.135506. Epub 2022 Jun 28.
In this study, a novel peracetic acid (PAA)-based advanced oxidation process using MnO as a catalyst was proposed. A thorough sulfamethoxazole (SMX) removal could be achieved within 12 min in MnO/PAA system at neutral pH. The characterization results of fresh and used MnO suggested that ≡Mn(II), ≡Mn(III) and ≡Mn(IV) on MnO were the Mn species for PAA activation, constituting the redox cycles of ≡Mn(II)/≡Mn(III) and ≡Mn(III)/≡Mn(IV) simultaneously. Organic radicals (i.e., CHC(O)O and CHC(O)OO) were verified to be the dominant reactive species responsible for SMX degradation in MnO/PAA system by radical scavenging experiments. The neutral condition was the most favorable pH for SMX removal in MnO/PAA system and the increase of PAA or MnO dosage could enhance SMX degradation. Presence of HCO and natural organic matter (NOM) could inhibit SMX degradation, while Cl, NO and SO had a negligible effect on SMX removal. The thorough SMX removal in successive experiments and characterization results of used MnO suggested the good reusability and stability of MnO for PAA activation. Based on six detected transformation products of SMX, hydroxylation, nitration, bond cleavage and coupling reaction were proposed to be its degradation pathways in MnO/PAA system.
在这项研究中，提出了一种使用 MnO 作为催化剂的新型过氧乙酸（PAA）高级氧化工艺。在中性 pH 值下，MnO/PAA 体系可在 12 分钟内彻底去除磺胺甲恶唑（SMX）。新鲜和使用过的 MnO 的特征化结果表明，MnO 上的 ≡Mn(II)、≡Mn(III)和 ≡Mn(IV)是 PAA 活化的 Mn 物种，同时构成了 ≡Mn(II)/≡Mn(III)和 ≡Mn(III)/≡Mn(IV)的氧化还原循环。通过自由基清除实验验证了有机自由基（即 CHC(O)O 和 CHC(O)OO）是 MnO/PAA 体系中负责 SMX 降解的主要活性物质。中性条件是 MnO/PAA 体系中 SMX 去除的最有利 pH 值，增加 PAA 或 MnO 用量可以增强 SMX 降解。HCO 和天然有机物（NOM）的存在会抑制 SMX 的降解，而 Cl、NO 和 SO 对 SMX 的去除几乎没有影响。连续实验中 SMX 的彻底去除和使用过的 MnO 的特征化结果表明，MnO 对 PAA 活化具有良好的可重复使用性和稳定性。基于检测到的 SMX 的六个转化产物，提出了在 MnO/PAA 体系中 SMX 的羟基化、硝化、键断裂和偶联反应的降解途径。
