Peracetic acid (PAA) has emerged as a new effective oxidant for various contaminants degradation through advanced oxidation process (AOP). In this study, sulfidated nano zero-valent iron-copper (S-nZVIC) with low Cu doping and sulfidation was synthesized for PAA activation, resulting in more efficient degradation of sulfamethoxazole (SMX, 20 μM) and other contaminants using a low dose of catalyst (0.05 g/L) and oxidant (100 μM). The characterization results suggested that S-nZVIC presented a more uniform size and distribution with fewer metal oxides, as the agglomeration and oxidation were inhibited. More significantly, doped Cu and sulfidation significantly enhanced the generation and contribution of •OH but decreased that of R-O• in S-nZVIC/PAA/SMX system compared with that of nZVIC and S-nZVI, accounting for the relatively high degradation efficiency of 97.7% in S-nZVIC/PAA/SMX system compared with 85.7% and 78.9% in nZVIC/PAA/SMX and S-nZVI/PAA/SMX system, respectively. The mechanisms underlying these changes were that (i) doped Cu° could promote the regeneration of Fe(Ⅱ) for strengthened PAA activation through mediating Fe(Ⅱ)/Fe(Ⅲ) cycle by Cu(Ⅰ)/Cu(Ⅱ) cycle; (ii) S species might consume part of R-O•, resulting in a decreased contribution of R-O• in SMX degradation; (iii) sulfidation increased the electrical conductivity, thus facilitating the electron transfer from S-nZVIC to PAA. Consequently, the dominant reactive oxygen species transited from R-O• to •OH to degrade SMX more efficiently. The degradation pathways, intermediate products and toxicity were further analyzed through density functional theory (DFT) calculations, liquid chromatography-mass spectrometry (LC-MS) and T.E.S.T software analysis, which proved the environmental friendliness of this process. In addition, S-nZVIC exhibited high stability, recyclability and degradation efficiency over a wide pH range (3.0∼9.0). This work provides a new insight into the rational design and modification of nano zero-valent metals for efficient wastewater treatment through adjusting the dominant reactive oxygen species (ROS) into the more active free radicals.

中文翻译：

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硫化纳米零价铁铜活化过乙酸时，掺杂 Cu0 和硫化诱导从 RO• 到•OH 的转变

过氧乙酸（PAA）已成为一种新的有效氧化剂，可通过高级氧化过程（AOP）降解各种污染物。在这项研究中，合成了具有低铜掺杂和硫化作用的硫化纳米零价铁铜（S-nZVIC）用于PAA活化，从而使用低剂量的磺胺甲恶唑（SMX，20μM）和其他污染物更有效地降解催化剂 (0.05 g/L) 和氧化剂 (100 μM)。表征结果表明，S-nZVIC 呈现出更均匀的尺寸和分布，金属氧化物更少，团聚和氧化受到抑制。更重要的是，与nZVIC和S-nZVI相比，掺杂Cu和硫化显着增强了S-nZVIC/PAA/SMX体系中•OH的生成和贡献，但降低了RO•的生成和贡献，导致其降解效率相对较高，达到97.7 S-nZVIC/PAA/SMX 系统中的 %，而 nZVIC/PAA/SMX 和 S-nZVI/PAA/SMX 系统中分别为 85.7% 和 78.9%。这些变化的机制是：（i）掺杂Cu°可以通过Cu（Ⅰ）/Cu（Ⅱ）循环介导Fe（Ⅱ）/Fe（Ⅲ）循环，促进Fe（Ⅱ）再生，从而增强PAA活化； (ii) S 物质可能会消耗部分 RO•，导致 RO• 对 SMX 降解的贡献减少； (iii)硫化增加了电导率，从而促进电子从S-nZVIC转移到PAA。因此，主要的活性氧从RO•转变为•OH，从而更有效地降解SMX。通过密度泛函理论（DFT）计算、液相色谱-质谱（LC-MS）和TEST软件分析进一步分析了降解途径、中间产物和毒性，证明了该过程的环境友好性。此外，S-nZVIC在较宽的pH范围（3.0∼9.0）内表现出较高的稳定性、可回收性和降解效率。这项工作通过将主要的活性氧（ROS）调整为更活跃的自由基，为合理设计和修饰纳米零价金属以实现高效废水处理提供了新的见解。