Exploring the impact of Cr3+ ions doping on optical, photocatalytic, and build-up factors of Co0.8-xZn0.2CrxFe2O4 nano-spinel ferrites

Abstract

This study investigates a nanoferrite system, Co_0.8-xZn_0.2CrₓFe₂O₄ (denoted as CoZnCrF), where x varies from 0.00 to 0.10 in increments of 0.02, synthesized using the citrate method. Diffuse reflectance spectroscopy analysis was employed to determine the optical band gap of the CoZnCrF ferrite nanoparticles, revealing an irregular trend with increasing Cr³⁺ incorporation. The optical band gap followed the order: Co_0.74Zn_0.2Cr_0.06Fe₂O₄ (1.83 ± 0.01 eV) > Co_0.72Zn_0.2Cr_0.08Fe₂O₄ (1.78 ± 0.01 eV) > Co_0.76Zn_0.2Cr_0.04Fe₂O₄ (1.76 ± 0.01 eV) > Co_0.8Zn_0.2Fe₂O₄ (1.75 ± 0.01 eV) > Co_0.78Zn_0.2Cr_0.02Fe₂O₄ (1.73 ± 0.01 eV) > Co_0.7Zn_0.2Cr_0.1Fe₂O₄ (1.72 ± 0.01 eV). This irregularity is attributed to variations in particle size and porosity within the CoZnCrF nanoferrites. The Co_0.7Zn_0.2Cr_0.1Fe₂O₄ nanoferrite exhibited exceptional degradation efficiency, achieving 97.60% for methylene blue (MB). The sample CoZnCrF-5 demonstrated the highest degradation efficiency (97.60%), which is attributed to its higher porosity and increased Cr³⁺ ion concentration in octahedral sites. The DE% after these five cycles was 97.60%, 97.29%, 96.84%, 96.51%, and 96.03%, respectively. The results provide direct evidence that the CoZnCrF-5 photocatalyst has improved recyclability and stability. The findings of this study provide clear evidence that the CoZnCrF-5 photocatalyst possesses enhanced recyclability and stability. This photocatalyst effectively removes toxic MB dye and holds potential for wastewater treatment applications. Furthermore, the variations in build-up factors with increasing Cr concentration at different penetration depths and photon energies showed insignificant differences across all nanoferrite samples.