Degradation of methylene blue by ellipsoidal β-FeOOH@MnO2 core-shell catalyst: Performance and mechanism

Abstract

An ellipsoidal β-FeOOH@MnO2 core-shell catalyst was synthesized and used to degrade methylene blue (MB). The ultra-thin less-crystalline MnO2 nanosheets loaded on the surface of ellipsoidal β-FeOOH were similar to corn-bracts, and the specific surface area of this catalyst has been significantly improved than β-FeOOH. β-FeOOH@MnO2 exhibited a certain removal rate of MB without peroxymonosulfate (PMS). Then, with the addition of PMS, the degradation rate of MB rapidly increased to 99% after 10 min in β-FeOOH@MnO2/PMS system, which is much higher than that in β-FeOOH/PMS system (51%). LC-MS/MS was used to investigate the degradation products, and a probable degradation pathway was proposed. According to FTIR, XPS and quenching studies, the redox processes of Fe3+/Fe2+ and Mn4+/Mn3+, as well as 1O2, O2−, OH and SO4− produced by catalyst-activated PMS, were found to be primarily responsible for the quick degradation of MB. However, 1O2 plays a key role. Generally, this research indicated that β-FeOOH@MnO2 was an efficient catalyst and had a potential application in practical wastewater treatment.