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

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