Rare earth-doped mixed Ni–Cu–Zn ferrites as an effective photocatalytic agent for active degradation of Rhodamine B dye

Abstract

In this study, a series of Gd3+-doped mixed Ni–Cu–Zn ferrites with composition of Zn0.5Ni0.3Cu0.2Fe2–xGdxO4 (x = 0, 0.025, 0.05, 0.075, 0.1) was prepared using self-ignition sol–gel method. The prepared nanoparticles with an average size ranging from 22 to 26 nm show a single-phase cubic structure belonging to the spinel matrix. A rise in the Gd3+ concentration leads to an increase in crystallite size and lattice parameter. In Fourier transform infrared spectra, two main absorption bands belonging to the spinel structure are observed. The high-frequency bands (υ1) represent the tetrahedral complex, while the low-frequency bands (υ2) signify the octahedral complex. The optical bandgap of the nanoferrites is found within the range of 2.91 to 2.41 eV, depending on their size. The magnetic characteristics of the material, such as saturation magnetization and coercivity are significantly altered with the concentration of Gd3+ in the solution. Using Rhodamine B (RhB) as a model organic pollutant, an in-depth investigation of the photocatalytic activity of the compounds was carried out. The present outcomes show that adding an adequate amount of Gd3+ significantly enhances the number of hydroxyl radicals produced by the ferrite, in turn, increasing the photocatalytic activity of the material. Mechanism elucidated by scavenger studies reveals that •OH and holes are the primary reactive radicals responsible for the degradation process. Prepared photocatalysts show an insignificant performance loss in five consecutive cycles. Thus, it is concluded that these photocatalysts are highly suitable for the remediation of dye-contaminated wastewater.