Enhanced photocatalytic degradation of tetracycline using Ag3PO4/ZnFe2O4 composite

Abstract The persistent presence of pharmaceutical contaminants in aquatic environments poses significant ecological and public health risks. Tetracycline (TC), a widely used broad-spectrum antibiotic in human medicine, veterinary applications, and aquaculture, is frequently detected in wastewater effluents due to the inefficiency of conventional treatment methods in its removal. In this study, a series of Ag₃PO₄/ZnFe₂O₄ heterojunction photocatalysts were synthesised at varying compositional ratios to enhance photocatalytic degradation of TC under visible light irradiation. The structural, morphological, compositional, and optical characteristics of the composites were systematically investigated using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS). The optimised Ag₃PO₄/ZnFe₂O₄ composite exhibited a significantly improved photocatalytic degradation efficiency of ~ 92% for TC, outperforming the pristine Ag₃PO₄ and ZnFe₂O₄, which achieved ~ 67% and ~ 47% degradation, respectively. Kinetic analysis revealed that the degradation followed pseudo-first-order kinetics. Radical scavenging experiments identified superoxide radicals (•O₂⁻) as the primary reactive species driving the degradation process. The enhanced performance was attributed to efficient charge separation facilitated by an S-scheme heterojunction mechanism. These findings demonstrate that the Ag₃PO₄/ZnFe₂O₄ composite is a promising and robust photocatalyst for effectively removing tetracycline from contaminated water systems.