Fenton-like catalyst Fe3O4@polydopamine-MnO2 for enhancing removal of methylene blue in wastewater

[Display omitted] •A novel Fenton-like catalyst Fe3O4@PDA-MnO2 was facilely synthesized.•This catalyst was applied in pH ranging from 2 to 12 in Fenton systems.•Fe3O4@PDA-MnO2 retained excellent reusability after 5 using-cycles.•The mechanism of Fe3O4@PDA-MnO2 removing methylene blue was proposed.•Fe3O4@PDA-MnO2 had good catalytic performance in practical application. Fenton technology has been proven an effective way to remove dyes from wastewater. However, the demanding pH of reaction condition restricted its wide application. In this study, we report a novel Fenton-like catalyst (Fe3O4@PDA-MnO2) facilely synthesized by polydopamine (PDA) coating and MnO2 depositing onto the surface of Fe3O4 nanoparticles. This method for preparing magnetic Fe3O4@PDA-MnO2 catalyst could avoid the agglomeration of MnO2 nanoparticles and make the catalyst collect easily from the solution. The resultant Fe3O4@PDA-MnO2 nanoparticles possess core-shell nanostructure. Fe3O4@PDA-MnO2 catalyst could cooperate with hydrogen peroxide to form a Fenton-like reagent for the removal of methylene blue (MB) and performed excellent catalytic activities towards MB, including high degradation efficiency of 97.36% after 240 min. Besides, Fe3O4@PDA-MnO2 can retain excellent reusability after 5 using-cycles. More importantly, the catalyst can be used in a wide pH range from 2 to 12 in Fenton systems, demonstrating that the degradation process is independent on pH which is different from most reported studies. Also, Fe3O4@PDA-MnO2 could still keep more than 75% removal efficiency of MB in industrial wastewater treatment application. Therefore, the synthesized Fe3O4@PDA-MnO2 would be a promising device for the removal of dyes from wastewater.