State Key Laboratory of Pollution Control and Resource Reuse, Nanjing University, Nanjing 210023, China; School of the Environment, Nanjing University, Jiangsu, Nanjing 210023, China.
State Key Laboratory of Pollution Control and Resource Reuse, Nanjing University, Nanjing 210023, China; School of the Environment, Nanjing University, Jiangsu, Nanjing 210023, China.
Sci Total Environ. 2022 Mar 15;812:151441. doi: 10.1016/j.scitotenv.2021.151441. Epub 2021 Nov 4.
Although manganese(II) is known to have no role in peroxymonosulfate (PMS) activation, through a series of sulfamethoxazole (SMX) oxidation experiments, we found that the addition of pyridine organic ligands can improve the catalytic activity and accelerate SMX oxidation. For the organic ligands to be effective: the stability constant of the Mn(III) complex should be higher than that of the Mn(II) complex. A positive correlation was observed between the SMX oxidation rate and Mn(II) concentration, and the maximum PMS utilization efficiency was achieved. Many shreds of evidence verified that neither •SO nor •OH was associated with SMX oxidation. The enhanced effect of phenanthroline on the Mn(II)/PMS system was attributed to the highly oxidative intermediate manganese species (Mn(V)), originating from the two-electron transfer reaction of complexed Mn(III) and PMS. Notably, the main oxidizing species did not change (η-(PMSO) ∼ 100%) regardless of the initial PMSO concentration or pH value. Additionally, the analysis of SMX degradation products revealed that the oxygen transfer oxidation pathway was dominant in the Mn(II)/phenanthroline/PMS system, while the N radical coupling pathway also contributed significantly to SMX oxidation. This work offers new insights into the formation of high-valent manganese species and provides a potential strategy for applying low-concentration Mn(II) to wastewater treatment.
虽然锰（II）已知在过一硫酸盐（PMS）活化中没有作用，但通过一系列磺胺甲恶唑（SMX）氧化实验，我们发现添加吡啶有机配体可以提高催化活性并加速 SMX 氧化。对于有机配体要起作用：Mn(III)配合物的稳定常数应高于 Mn(II)配合物。SMX 氧化速率与 Mn(II)浓度之间存在正相关关系，并且实现了最大的 PMS 利用率。大量证据证明，SMX 氧化与 •SO 或 •OH 均无关。邻菲啰啉对 Mn(II)/PMS 体系的增强作用归因于来自配合的 Mn(III)和 PMS 的两电子转移反应的高氧化性中间锰物种（Mn(V)）。值得注意的是，无论初始 PMSO 浓度或 pH 值如何，主要氧化物质都没有改变（η-(PMSO)∼100%）。此外，SMX 降解产物的分析表明，在 Mn(II)/邻菲啰啉/PMS 体系中，氧转移氧化途径占主导地位，而 N 自由基偶联途径也对 SMX 氧化有显著贡献。这项工作为高价锰物种的形成提供了新的见解，并为应用低浓度 Mn(II)处理废水提供了一种潜在的策略。
