Jie Zhang,Mengchen Zong,Ben Dong,Sijie Ge,Shilong He
Quinoline, as one of the typical toxic and refractory organic pollutants in coal chemical industry wastewater, poses a significant threat to human health and environmental quality. In this study, MnCexOy and MnFexOy catalysts were successfully synthesized by doping Ce3+ and Fe2+ into α-MnO2 at a molar ratio of 1∶10 and were applied to the process of catalytic ozonation for the degradation of quinoline. Additionally, a variety of characterization techniques were employed to elucidate the characteristics of the catalysts, including scanning electron microscopy, X-ray diffraction, Brunauer–Emmett–Teller (BET) analysis, X-ray photoelectron spectroscopy, H2-TPR, NH3-TPD. The results show that, in the catalytic ozonation system for quinoline removal, MnCexOy demonstrates excellent quinoline removal efficiency of 87.45%, which is higher than that of MnFexOy (78.83%) and unmodified α-MnO2 (62.67%). By introducing the surface hydroxyl masking agent HPO42−, the significant role of surface hydroxyl groups and oxygen vacancies in the catalytic degradation of quinoline by MnCexOy was further demonstrated. Exploring the surface characteristics of catalysts is beneficial for continued understanding of the active centers of catalysts. Research results will be helpful to the deep treatment and reuse of tailing water of coking wastewater.
View large Download slide View large Download slide Close modal Quinoline inevitably remains in the effluent of coking wastewater treatment plants due to its bio-refractory nature, which might cause unfavorable effects on human and ecological environments. In this study, MnCe x O y was consciously synthesized by α -MnO 2 doped with Ce 3+ (Ce:Mn = 1:10) and employed as the ozonation catalyst for quinoline degradation. After that, the removal efficiency and mechanism of quinoline were systematically analyzed by characterizing the physicochemical properties of MnCe x O y , investigating free radicals and monitoring the solution pH. Results indicated that the removal rate of quinoline was greatly improved by the prepared MnCe x O y catalyst. Specifically, the removal efficiencies of quinoline could be 93.73, 62.57 and 43.76%, corresponding to MnCe x O y , α -MnO 2 and single ozonation systems, respectively. The radical scavenging tests demonstrated that • OH and • O 2 - were the dominant reactive oxygen species in the MnCe x O y ozonation system. Meanwhile, the contribution levels of • OH and • O 2 - to quinoline degradation were about 42 and 35%, respectively. The abundant surface hydroxyl groups and oxygen vacancies of the MnCe x O y catalyst were two important factors for decomposing molecular O 3 into more • OH and • O 2 - . This study could provide scientific support for the application of the MnCe x O y /O 3 system in degrading quinoline in bio-treated coking wastewater. MnCe x O y Ce 3+ , MnCe x O y • OH and • O 2 - MnCe x O y were successfully synthesized by α-MnO 2 doped with Ce 3+ . The by abundant oxygen vacancies and surface hydroxyl groups of the MnCe x O y catalyst enhanced its catalytic activity. • OH and • O 2 - formation contributed to quinoline degradation in the MnCe x O y ozonation system.
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