Impact of Calcination Temperature on Structural and Optical Properties and Photocatalytic Efficiency of Ni_0.33Cu_0.33Zn_0.33Fe₂O₄ Nanoparticles in Aniline Degradation

In this study, the structural and optical properties as well as the photocatalytic performance of Ni_0.33Cu_0.33Zn_0.33Fe₂O₄ nanoparticles were investigated. These nanoparticles were prepared using the co-precipitation method by applying different calcination temperatures (773, 823, 873, 923, and 973 K). The X-ray diffraction analysis confirmed the presence of the cubic spinel ferrite phase without secondary phases. As the calcination temperature increased from 773 to 973 K, the crystallite and particle sizes of Ni_0.33Cu_0.33Zn_0.33Fe₂O₄ nanoparticles increased from 12.84 to 20.19 nm and from 19.13 to 43.83 nm, respectively. Among the prepared samples, Ni_0.33Cu_0.33Zn_0.33Fe₂O₄ nanoparticles calcined at 873 K revealed the highest value of band gap energy along with the lowest values of Urbach energy, refractive index, and optical and static dielectric constant. Additionally, the prepared samples were applied as photocatalysts for the degradation of aniline under ultraviolet irradiation. Improved photocatalytic performance was revealed by Ni_0.33Cu_0.33Zn_0.33Fe₂O₄ nanoparticles calcined at 873 K. This was attributed to the slowest recombination rate of the electron–hole pairs as revealed from PL analysis. To further improve the photodegradation rate, the degradation reaction was studied by varying the catalyst amount, aniline concentration, pH mediums, and reaction temperatures. Increasing the pH and temperature boosted the degradation rate. Finally, the degradation reaction was carried out by incorporating Ni_0.33Cu_0.33Zn_0.33Fe₂O₄ nanoparticles calcined at 873 K with different weight % of carbon quantum dots. The results revealed enhanced photocatalytic activity with k = 30 × 10⁻⁴ min⁻¹ was achieved after combining 10 weight % of carbon quantum dots with Ni_0.33Cu_0.33Zn_0.33Fe₂O₄ nanoparticles.