Dai Yinshun, Du Weiyu, Jiang Chao, Wu Wanqi, Dong Yamin, Duan Liangfeng, Sun Shiwen, Zhang Baiyu, Zhao Shan
Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong, 266237, China.
The Northern Region Persistent Organic Pollution (NRPOP) Control Laboratory, Faculty of Engineering and Applied Science, Memorial University of Newfoundland, St. John's, NL A1B 3 × 5, Canada.
Water Res. 2023 Apr 15;233:119743. doi: 10.1016/j.watres.2023.119743. Epub 2023 Feb 15.
Crystalline iron sulfide (FeS, i.e., FeS or FeS) minerals as sulfur sources were used to prepare the mechanochemically sulfidated microscale zero-valent iron ((FeS+ZVI)). Metastable FeS and FeS precursors were generated via aqueous coprecipitation and applied to fabricate FeS@ZVI samples. (FeS+ZVI) and FeS@ZVI exhibited better chloramphenicol (CAP) degradation than ZVI due to the increase in specific surface areas, the decrease of electrochemical impedance, the formation of galvanic cells, and sulfur-induced pitting and local acidity. (FeS+ZVI) had better CAP removal capacity than FeS@ZVI under different S/Fe molar ratios, initial pH, and oxygen conditions. At the same time, FeS@ZVI showed better electron utilization under oxic conditions, related to their Fe and sulfur spatial distribution. Nitro reduction and dechlorination of CAP by (FeS+ZVI) produced nitroso, azoxy, amine, and monodechlorination products, while dechlorination was not involved in the degradation process of CAP by FeS@ZVI. A new transformation pathway of nitroso-CAP to amine-CAP mediated by azoxy products is proposed via coupling a chain decay multispecies model and DFT calculations. The larger competitive reaction rates among O, CAP, and its degradation products was determined by their lower LUMO energy. The contribution of direct electron transfer to nitro reduction was greater than that of atomic hydrogen, but the opposite was true for dechlorination. FeS@ZVI had a larger DET contribution than (FeS+ZVI), and FeS promoted the DET contribution better than FeS. Toxicity assessment indicated that the rapid transformation of nitroso and azoxy products was crucial for eliminating the biotoxicity of CAP.
以结晶硫化铁（FeS，即FeS或FeS）矿物作为硫源来制备机械化学硫化的微米级零价铁（(FeS+ZVI)）。通过水相共沉淀生成亚稳的FeS和FeS前驱体，并用于制备FeS@ZVI样品。由于比表面积增加、电化学阻抗降低、原电池形成以及硫诱导的点蚀和局部酸度，(FeS+ZVI)和FeS@ZVI对氯霉素（CAP）的降解效果优于零价铁（ZVI）。在不同的S/Fe摩尔比、初始pH值和氧气条件下，(FeS+ZVI)的CAP去除能力优于FeS@ZVI。同时，FeS@ZVI在有氧条件下表现出更好的电子利用效率，这与其铁和硫的空间分布有关。(FeS+ZVI)对CAP的硝基还原和脱氯产生了亚硝基、偶氮氧基、胺和单脱氯产物，而脱氯不参与FeS@ZVI对CAP的降解过程。通过耦合链式衰减多物种模型和密度泛函理论（DFT）计算，提出了由偶氮氧基产物介导的亚硝基-CAP向胺-CAP的新转化途径。O、CAP及其降解产物之间较大的竞争反应速率是由它们较低的最低未占分子轨道（LUMO）能量决定的。直接电子转移对硝基还原的贡献大于原子氢，但对脱氯的贡献则相反。FeS@ZVI的直接电子转移（DET）贡献比(FeS+ZVI)大，且FeS比FeS更能促进DET贡献。毒性评估表明，亚硝基和偶氮氧基产物的快速转化对于消除CAP的生物毒性至关重要。
