Improved photocatalytic performance of Ce substituted lanthanum ferrite nanoparticles for the degradation of harmful antibiotic tetracycline from water

Abstract

Antibiotics, a widely used pharmaceutical, directly endanger aquatic environment and human health, when discharged into water bodies from pharmaceutical industries, hospitals and breeding farms. To address this issue, several semiconductor materials are employed as photocatalysts to degrade antibiotics effectively. The present study focuses on the synthesis of Ce-substituted lanthanum ferrites in different compositions [La_1-xCe_xFeO₃ (x = 0.0, 0.1, 0.2, 0.3)] by hydrothermal method for the effective degradation of tetracycline. The structural, morphological, compositional and optical properties of prepared photocatalysts were characterised by X-ray Diffraction, Fourier transform infrared spectroscopy, High-resolution scanning electron microscopy, High-resolution transmission electron microscopy, Energy dispersive X-ray spectroscopy and Ultraviolet diffuse reflectance spectroscopy respectively. XRD validated the orthorhombic crystal structure of nanoparticles in the Pbnmspace groupwith the reduction of average crystallite size from 32.74 to 24.97 nm upon Ce substitution. FTIR verified the presence of the distinctive Fe-O bond. The morphological study also revealed that the materials were porous. The samples were identified as visible-light-driven photocatalysts, with the reduction of optical band gap from 2.24 to 1.88 eV with increasing Ce concentration. The role of visible light exposure on synthesized nanoparticles was studied. Bare lanthanum ferrite degraded only 56 % of tetracycline. However, cerium-substituted lanthanum ferrite nanoparticles have shown maximum degradation of 91 %. The estimated degradation rate constant of La_0.8Ce_0.2FeO₃ was found to be 3 times greater than the bare sample and follows pseudo-first order kinetics.The main active species involved in degradation was identified as superoxide radicals. Reusability studies confirmed the structural chemical stability of the samples over multiple degradation cycles, rendering its usage as efficient photocatalyst in wastewater treatment systems for the degradation of tetracycline.