Visible-light-driven Z-scheme tungsten oxide/ silver phosphate/ coffee bean biochar photocatalyst for simultaneous degradation of ciprofloxacin and chlorpyrifos

Abstract

The integration of biochar as a solid-state electron mediator in Z-scheme photocatalytic systems represents a promising approach for the efficient degradation of organic contaminants. In this study, a novel magnetic Z-scheme photocatalyst, silver phosphate–tungsten oxide (Ag₃PO₄–WO₃)/coffee bean biochar composite (ABW-10), was synthesized via a hydrothermal method. Ag₃PO₄ and WO₃ were immobilized onto biochar layers to facilitate charge separation and enhance electron transfer under visible light irradiation. Morphological analysis confirmed a uniformly decorated biochar surface with well-dispersed nanoparticles, supporting efficient photocatalytic performance. Mott–Schottky plots revealed improved charge carrier dynamics and conductivity. Radical scavenging experiments validated the Z-scheme charge transfer mechanism, confirming the generation of reactive oxygen species. ABW-10 exhibited exceptional photocatalytic activity, achieving nearly 100% mineralization of ciprofloxacin (50 ppm) and chlorpyrifos (20 ppm) within 60 minutes under ambient conditions at a catalyst dosage of 0.1 g. LC-MS analysis elucidated the degradation pathways of both pollutants. Additionally, the composite demonstrated excellent reusability and a fivefold increase in antimicrobial activity against both Staphylococcus aureus and Escherichia coli compared to the individual components.