Investigation of structural, optical, and magnetic properties of NiFe2O4 for efficient photocatalytic degradation of organic pollutants through photo fenton reactions

Nowadays, water pollution generated from textile effluents is one of the major problems for the human race and ecology. Hence, development of sustainable strategies to lower the water pollution level has become a burning need. In this regard, the present study focuses on the preparation of nano catalyst NiFe₂O₄ to catalyze the chemical reactions on industrial organic dyes for their fast cleansing from water. By sol-gel auto-combustion technique, NiFe₂O₄ nanoparticles were synthesized and exposed to thermal process at temperatures of 400, 600, and 800 °C. Highly crystalline phase with spinel cubic structured NiFe₂O₄ was formed with a crystal size of 18.71 nm, which was confirmed by XRD analysis. The FTIR spectra showed two fundamental absorption bands in the range 597.80-412.59 cm^-1, which are the characteristics of tetrahedral M - O and octahedral M - O bond in NiFe₂O₄. The surface morphology of calcined NiFe₂O₄ was investigated by scanning electron microscope (SEM). The nanoparticle size analyzer exhibited that the synthesized NiFe₂O₄ nanoparticles had an average particle size of ∼ 291.3 nm. Three stage decomposition patterns were observed for NiFe₂O₄, which was analyzed by a temperature programmed STA. Zeta potential analyzer showed that the synthesized sample S1 and S2 were stable in the dispersion medium. Also, NiFe₂O₄ exhibited optical band gap energies for direct band transitions within the visible spectrum measured to be 1.43-1.45 eV, rendering them effective as photocatalysts under sunlight. The samples showed magnetic measurements by VSM with saturation magnetization, coercivity, remnant magnetization value of 66.81 emu/g, 4.13 Oe and 12.94 emu/g, respectively. The synthesized photocatalyst, NiFe₂O₄, at 400 °C, significantly degraded three toxic organic pollutants-Methylene blue, Rhodamine B, and Congo Red-under visible light through 'Photo-Fenton' reaction mechanisms. Among the three dyes, Methylene Blue exhibited the highest degradation percentage with a rate constant of 0.0149 min^-1 and followed pseudo-first-order kinetic model.