Fabrication of visible light-driven magnetically separable Ag3PO4/Fe3O4/g-C3N4 photo catalyst for tetracycline degradation

Abstract

The growing presence of antibiotics in wastewater is a major environmental concern, highlighting the need for effective methods to break them down. This study explores the photocatalytic performance of a Z-scheme Ag₃PO₄/Fe₃O₄/g-C₃N₄ nanocomposite for the removal of tetracycline (TC), a widely used antibiotic and emerging water pollutant. The nanocomposite was prepared using a simple physical mixing approach, ensuring uniform dispersion and strong interfacial interaction among the components. Comprehensive characterization methods including XRD, FTIR, SEM, TEM, BET, VSM, and UV–vis spectroscopy confirmed the formation of a well-structured ternary system with large surface area, efficient visible-light absorption, and superparamagnetic properties, with a saturation magnetization of 3.241 emu g⁻¹. Under optimal photocatalytic conditions (TC concentration: 10 ppm, catalyst dose: 40 mg, pH = 7), the photocatalyst achieved a high degradation efficiency of 94.32% within 90 min. The reaction followed pseudo-first-order kinetics with a calculated rate constant of 0.0307 min⁻¹. This improved efficiency is ascribed to the synergistic interaction of Fe₃O₄, Ag₃PO₄, and g-C₃N₄ constructing a Z-scheme heterojunction. This structure facilitates efficient charge carrier separation, enhances light absorption, and increases the number of active sites by expanding the surface area. Radical scavenging experiments identified superoxide (^●O₂⁻) and hydroxyl (^●OH) radicals as the key reactive species, confirming the operation of a Z-scheme charge transfer mechanism that enhances charge separation and suppresses recombination. The catalyst demonstrated excellent reusability, retaining 86.98% of its photocatalytic activity after five consecutive cycles. These results highlight the potential of Ag₃PO₄/Fe₃O₄/g-C₃N₄ as a robust, magnetically separable, and environmentally friendly photocatalyst for efficient antibiotic removal from wastewater.