Facile synthesis of graphene anchored rare earth doped mixed metal ferrite nanorods: A potential candidate for azo dye mineralization

Bandgap tuning using rare earth metals as dopants in ferrite-based photocatalytic materials has received a lot of interest because the Fermi 4f energy of these metals generates a sub-energy state in the bandgap generated by the overlapping of Fe-3d and O-2p orbitals. Herein, dysprosium-doped cobalt-nickel mixed ferrite (D-CNFO) and its graphene-reinforced composite (D-CNFO@G) were prepared and an ideal photocatalyst material for azo dye mineralization was proposed. A cost-effective combination of wet-chemical and ultrasonication methods was used to prepare the doped and composite samples. Advanced characterization methodologies were used to scrutinize the optical, compositional, structural, morphological, and photocatalytic characteristics of as-prepared materials. The X-ray diffraction analysis identified the spinel phase's (cubic) structure, while the electronic spectroscopy examination confirmed the prepared samples' rod-like morphology. The UV/visible absorbance spectrum shows the higher light harvesting behavior of the G-CNFO@G in the visible region. The mineralization performance of the D-CNFO and D-CNFO@G composites was analyzed using Congo-red (an anionic dye), a well-known azo dye. The D-CNFO@G sample removes Congo-red dye at a rate almost 2.4% faster than the G-CNFO sample. The experiment involving trapping free radicals indicates that hydroxyl radical plays a crucial role in dye degradation. Since the G-CNFO@G catalyst is magnetic and can be isolated easily from the photocatalytic system, it shows an awkward cycle activity of more than 96% after five mineralization tests. The as-prepared D-CNFO@G composite is proved as an excellent option for azo dye mineralization because of the combined impacts of rare earth doping, graphene reinforcement and nanotechnology.