Erbium-substituted Ni_0.4Co_0.6Fe₂O₄ ferrite nanoparticles and their hybrids with reduced graphene oxide as magnetically separable powder photocatalyst

New Ni_0.4Co_0.6Er_0.045Fe_1.95O₄ spinel ferrite nanoparticles and their hybrids with reduced graphene oxide (rGO) nanohybrids were prepared by simple, low cost surfactant assisted co-precipitation and sonication method respectively. The synthesized materials were characterised by X-ray diffraction (XRD) analysis, Fourier transforms infrared spectroscopy (FTIR), UV–Visible and vibrating sample magnetometeric (VSM) measurements. XRD analysis confirmed the face centered (FCC) spinel ferrites that are further supported by FTIR results. The optical bandgap of nano-crystallites was around 2.66 eV that enable it to be active in both Ultraviolet and Visible spectrum of light. Photocatalytic efficiency was tested for both Ni_0.4Co_0.6Er_0.045Fe_1.95O₄ ferrite nanoparticles and their graphene based hybrid material using methylene blue as typical organic pollutant as proof of principle. Results showed noticeable photocatalytic degradation up to 31.96% in the case of Ni_0.4Co_0.6Er_0.045Fe_1.95O₄ nano-crystallites. Furthermore, photocatalytic activity was improved up to 43.1% by graphene based hybrid of Ni_0.4Co_0.6Er_0.045Fe_1.95O₄ nano-crystallites. This exceptional increase in activity was due to lowering of charge carrier recombination at photocatalyst surface, adsorption of more and more dye molecules by large surface area of graphene and easy transmission of electrons from metal valence band to conduction band.