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

• Published in: Journal of rare earths Vol. 42; no. 3; pp. 488 - 496
• Main Authors: Jadhav, Swapnil A., Somvanshi, Sandeep B., Gawali, Sudarshan S., Zakde, Kranti, Jadhav, K.M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2024
• Subjects: Gd3+ substitution; Magnetic properties; Photocatalysis; Rare earths; Spinel ferrite; Structural properties; Gd3+ substitution; Rare earths; Photocatalysis; Structural properties; Spinel ferrite; Magnetic properties
• ISSN: 1002-0721; 2509-4963
• DOI: 10.1016/j.jre.2023.03.004

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. When the photocatalyst Zn0.5Ni0.3Cu0.2Fe2–xGdxO4 absorbs the sun light, it produces pairs of electron and holes. The electron of the valence band of Zn0.5Ni0.3Cu0.2Fe2–xGdxO4 becomes excited when illuminated by the sunlight. The excess energy of this excited electron promotes the electron to go to the conduction band of Zn0.5Ni0.3Cu0.2Fe2–xGdxO4 which creates the negative electron e– and positive hole h+ pair. This stage is referred as the semiconductors photo excitation state. The positive hole of Zn0.5Ni0.3Cu0.2Fe2–xGdxO4 breaks apart the water molecules to form hydrogen gas and hydroxyl radical. The negative electron reacts with oxygen molecules to form super oxide anion. This reaction continues when sunlight is available. [Display omitted]