A facile synthesis of Mn3O4/Fe3O4 superparamagnetic nanocomposites by chemical precipitation: Characterization and application in dye degradation

Abstract Degradation of methylene blue (MB) is investigated using Mn 3 O 4 as an oxidant. Discrete Mn 3 O 4 particles and Mn 3 O 4 /Fe 3 O 4 nanocomposites are synthesized via coprecipitation by using air as an oxidant in the absence and presence of previously synthesized magnetite nanoparticles, respectively. Characterization results show that superparamagnetic magnetite nanoparticles of ∼10 nm were synthesized. The Mn 3 O 4 synthesis in the presence of these magnetite nanoparticles favors the formation of a pure, highly ordered Mn 3 O 4 /Fe 3 O 4 superparamagnetic nanocomposite, which can be separated by an external magnetic field. This nanocomposite is applied to the oxidative decolorization of methylene blue (MB) and is capable of catalyzing the complete N -demethylation of MB, forming thionine as the final product and removing 93% of the dye in approximately 1 h.