Super-fast degradation of high concentration methyl orange over bifunctional catalyst Fe/Fe3C@C with microwave irradiation

[Display omitted] •Fe/Fe3C@C served both as the catalyst and microwave absorber for highly efficient methyl orange degradation.•The calcination temperature is a crucial factor determining the composition and microstructure of the Fe/Fe3C@C.•In situ generated free radicals over Fe/Fe3C@C is responsible for the degradation of methyl orange. Bifunctional catalyst Fe/Fe3C@C with magnetism was successfully prepared by sol-gel method and proved to degrade methyl orange with high efficiency under microwave irradiation. The Fe/Fe3C@C catalysts calcined at 500 °C, 600 °C, 700 °C were intensively characterized and compared in their crystalline structure, porosity, morphology and dielectric property. The results imply a phase and structure transformation in the materials as the calcination temperature increased. Fe/Fe3C@C-700 exhibited a core-shell structure and an apparent Fe3C phase. In addition, Fe/Fe3C@C-700 demonstrated excellent dielectric property as a microwave absorber than Fe/Fe3C@C-500 and Fe/Fe3C@C-600. At the same time, it gave a 100 % removal rate in 30 s for the degradation of methyl orange under microwave irradiation, outperformed the Fe/Fe3C@C-500 and Fe/Fe3C@C-600 and most other reported catalysts in similar studies. The possible mechanism of the methyl orange degradation should be ascribed to the in situ generation of •OH and O2•− active species over the Fe/Fe3C@C catalyst. The excellent microwave absorbing property of Fe/Fe3C@C-700 could also boost its catalytic activity and play a critical role during the super-fast microwave-assisted degradation process. The findings in this study could be informative for the development of a continuous process of dye wastewater treatment for industrial implementation.