Efficient degradation of Acid Orange 7 by persulfate activated with a novel developed carbon‐based MnFe₂O₄ composite catalyst

Abstract

Abstract BACKGROUND A novel carbon‐based modified MnFe 2 O 4 catalyst was first developed to produce sulfate radicals (SO 4 −• ) by activation of persulfate (PS). The catalyst was fabricated with a mixture of MnFe 2 O 4 nanoparticles and chitosan (which could form a large amount of carbon‐based biomass after pyrolysis) annealed at 600 °C and was referred to as CM‐600. RESULTS The microstructure of the composite catalyst CM‐600 showed that MnFe 2 O 4 was supported on the surface of carbon‐based sheets. After modification by pyrolysis, the specific surface area of MnFe 2 O 4 enlarged significantly and thus the contact area between catalyst and PS increased. X‐ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy and X‐ray photoelectron spectroscopy were used to characterize the components of CM‐600. In comparison with the MnFe 2 O 4 /PS system, the activation of PS by CM‐600 was enhanced prominently, while 99.0% Acid Orange 7 (AO7) removal was achieved after reacting for 30 min. Investigations of influencing factors indicated the optimal treatment parameters. The two reactive species in the degradation process, namely free radicals (SO 4 −• and hydroxyl radicals ( • OH)) and non‐radicals (singlet oxygen, 1 O 2 ), were confirmed by quenching tests and electron spin resonance spectroscopy. The corresponding degradation mechanism was proposed and SO 4 −• was generated primarily via the activation of PS by Mn II and Fe II . CONCLUSION The research demonstrated that the composite catalyst CM‐600 improved the property of MnFe 2 O 4 for catalyzing PS and thus enlarged the practical application of SO 4 −• oxidation technology in pollutant degradation in aqueous environments. © 2019 Society of Chemical Industry