Abstract：
Permanganate [Mn(VII)] has gained broad attention in water treatment. However, its limited reactivity toward some refractory micropollutants hinders its application for micropollutant degradation. Herein, we introduced UVA-LED photolysis of Mn(VII) (UVA-LED/Mn(VII)) to degrade micropollutants (diclofenac (DCF), 4-chlorophenol (4-CP), atrazine, and nitrobenzene) by selecting DCF and 4-CP as target micropollutants. The effects of operating conditions (e.g., light intensity, radiation wavelengths, pH, and water constituents) on DCF and 4-CP degradation as well as the underlying mechanisms were systematically studied. The degradation rates of DCF and 4-CP linearly decreased with increasing radiation wavelengths (from 365 to 405 nm), likely due to the decreased molar absorption coefficients and quantum yields of Mn(VII). Reactive manganese species (RMnS), including Mn(V), Mn(III), and HO•, were generated in the UVA-LED/Mn(VII) process. Mn(V) and HO• were responsible for DCF degradation, while Mn(III), HO•, and likely Mn(V) accounted for 4-CP degradation. Competitive kinetic results revealed that contributions of RMnS and HO• decreased with increasing radiation wavelengths, wherein RMnS played the dominant role. Increasing pH displayed opposite effects on DCF and 4-CP degradation with higher degradation efficiency obtained at acidic pH for the former one but alkaline pH for the latter one. The presence of water background ions (e.g., Cl-, HCO3-, and Ca2+) barely influenced DCF and 4-CP degradation. Finally, in comparison with Mn(VII) alone, enhanced degradation of DCF and 4-CP by UVA-LED/Mn(VII) was observed in real waters. This work advances the understanding of the photochemistry of manganese species in micropollutant degradation and facilitates Mn(VII) oxidation in practical application.
摘要：
高锰酸盐[Mn(VII)]在水处理中受到广泛关注。然而,其对某些难降解的微污染物的有限反应性阻碍了其在微污染物降解中的应用。在这里，我们引入了UVA-LED光解Mn(VII)(UVA-LED/Mn(VII))来降解微污染物(双氯芬酸(DCF),4-氯苯酚(4-CP),阿特拉津,和硝基苯）通过选择DCF和4-CP作为目标微污染物。操作条件的影响(例如，光强度,辐射波长，pH值,和水成分）对DCF和4-CP降解以及潜在机理进行了系统研究。DCF和4-CP的降解速率随着辐射波长的增加（从365到405nm）线性下降，可能是由于Mn（VII）的摩尔吸光系数和量子产率降低。反应性锰物种（RMnS），包括Mn(V)，Mn(III),和HO•，在UVA-LED/Mn(VII)过程中产生。Mn(V)和HO•是DCF降解的原因，而Mn(III)，HO•,Mn（V）可能是4-CP降解的原因。竞争动力学结果表明，RMnS和HO•的贡献随着辐射波长的增加而降低，其中RMnS起主导作用。增加pH对DCF和4-CP降解表现出相反的影响，前者在酸性pH下获得更高的降解效率，而后者在碱性pH下获得更高的降解效率。水背景离子的存在(例如，Cl-,HCO3-,和Ca2）几乎不影响DCF和4-CP降解。最后,与单独的Mn(VII)相比，在真实水域中观察到UVA-LED/Mn（VII）对DCF和4-CP的降解增强。这项工作促进了对锰物种在微污染物降解中的光化学的理解，并促进了实际应用中的Mn（VII）氧化。
