Flower-like core-shell Fe3O4@MnO2 microspheres: Synthesis and selective removal of Congo red dye from aqueous solution

Flower-like core-shell MnO2-coated magnetic composites (Fe3O4@MnO2) were prepared via a simple hydrothermal process. Fe3O4@MnO2 composites could selective removal of Congo red from aqueous solution involving various dyes (Congo red (CR), methylene blue (MB), methyl orange (MO), crystal violet (CV), and rhodamine B (RB)). The maximum removal rate of CR was 95% (wt%) and larger than that of other dyes (< 15%).130