Jianhui Zhao,Yuanzhou Wang,Ning Li,Shaopo Wang,Junli Yu,Xinxin Li
In this work, the magnetic γ-Fe 2 O 3 –MnO 2 bifunctional catalyst with oxygen vacancy was synthesized for peroxymonosulfate (PMS) activation under visible light. The activity of γ-Fe 2 O 3 –MnO 2 was investigated by ciprofloxacin (cipro) degradation. Results showed that 98.3% of cipro (50 μM) was removed within 30 min in visible-light/PMS system mediated by γ-Fe 2 O 3 –MnO 2 (2:1) with fine-tuned oxygen vacancy. The cipro degradation data fitted well with pseudo-first-order kinetic model with the highest kinetic constant of 0.114 min −1 . Besides, the γ-Fe 2 O 3 –MnO 2 exhibited stability, recyclability and practicability. High selectivity for cipro degradation was observed with coexisting anions in visible-light/γ-Fe 2 O 3 –MnO 2 /PMS system. Furthermore, the enhanced mechanism of PMS activation under visible light with γ-Fe 2 O 3 –MnO 2 was proposed. The appropriate oxygen vacancy enhanced the separation of photo-induced carriers and Z scheme heterostructure maintained the highest redox potential . Accordingly, the synergistic effect of photocatalysis and PMS activation enhanced cipro degradation. Free radical and non-radical species including , h + , 1 O 2 , • OH and co-existed in the coupled system. Impressively, this study provides a handy approach for oxygen vacancy regulation in metallic oxides composite and an easily recycled catalyst with high-activity in coupled oxidation system towards antibiotic degradation.
Jiankang Wang,Taiping Xie,Guokang Han,Quanxi Zhu,Yajing Wang,Yuan Peng,Songli Liu,Zhongping Yao
Cost-effective and low-toxicity of MnO 2 is regarded as a promising alternative to Co-based catalyst for peroxymonosulfate (PMS) activation to degrade recalcitrant organic pollutants. However, the sluggish Mn(IV)/Mn(III) redox cycling and limited specific surface area greatly hampered its wide application. To solve this challenge, a mesoporous γ-Fe 2 O 3 @MnO 2 magnetic catalyst with SiO 2 assistance (s-γ-Fe 2 O 3 @MnO 2 ) was synthesized. Physicochemical characterization confirmed part MnO 2 was coated on γ-Fe 2 O 3 surface while the other existed independently. Furthermore, BET surface area of s-γ-Fe 2 O 3 @MnO 2 was more than two times that of the counterpart without SiO 2 assistance (ws-γ-Fe 2 O 3 @MnO 2 ). s-γ-Fe 2 O 3 @MnO 2 exhibited enhanced PMS activation capacity with 97.6% phenol removal efficiency within 80 min, superior to other samples. Various influencing parameters on phenol oxidation were optimized. Reactive oxygen species (ROS) scavenging experiment and electron paramagnetic resonance (EPR) validated co-existence of hydroxyl radicals (·OH) and sulfate radicals (SO 4 · − ) as well as singlet oxygen ( 1 O 2 ) during PMS activation. However, phenol degradation was a non-radical oxidation process dominated by 1 O 2 . A rational reaction mechanism was proposed. Fe(II) promoted Mn(IV)/Mn(III) redox cycling and the enlarged surface area derived from SiO 2 mediated templating synthesis were responsible for the enhanced phenol degradation. This strategy can give a guidance for synthesis of highly efficient catalyst for sewage remediation.
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