Temperature controlled synthesis of Co-Ni mixed ferrite nanostructure for the mineralization of azo dye: A novel and facile approach

Abstract

Herein, Co-Ni mixed spinel ferrite (Co0.5Ni0.5Fe2O4, CNFO) nanostructures were synthesized via wet-chemical route followed by an annealing process. The products were annealed at three different temperatures (550, 650, and 750 °C) to obtain CNFO-550, CNFO-650, and CNFO-750 ferrites samples. XRD and FTIR analyses show that mixed ferrites samples have a cubic crystalline system with crystallite sizes ranging from 14.3 to 16.3 nm and exhibit all the spinel structure's characteristic vibrational modes. FESEM and EDX techniques were used to confirm that the mixed ferrites had a nano-structured morphology and an impurity-free composition. The light-harvesting characteristics, and associated band gap values for the CNFO-550, CNFO-650, and CNFO-750 ferrites samples were investigated by UV/Visible studies. The photocatalytic studies of all prepared ferrites were examined using Cong-red dye under solar illumination. The CNFO-550 and CNFO-650 materials showed relatively lower mineralization efficiency after 90 min of solar illumination, whereas the highest CR-dye mineralization efficiency was achieved with the CNFO-750 sample. The photocatalytic activity of the CNFO-750 sample has not changed significantly after five subsequent reusability tests. Actually, ferrite material is stable and completely recovers due to its unique crystal structure and magnetic behavior. The scavenging test proposed the hydroxyl radical as the most active species actively involved in the CR-dye degradation process. Our CNFO-750 material is easy to prepare, works well as a photocatalyst against azo dyes, and can be used many times. This suggests that one could use the CNFO-750 ferrite sample on a large scale to treat textile effluents.