Visible-light-driven photocatalytic degradation of ofloxacin using AgCl/ZnO heterojunction composites

Antibiotics are persistent emerging contaminants that are difficult to remove using conventional wastewater treatment methods, thereby posing potential risks to aquatic environments and human health. In this study, an AgCl/ZnO heterojunction photocatalyst was successfully synthesized via a co-precipitation method for the visible-light-driven degradation of ofloxacin (OFL). Structural and optical characterizations confirmed the successful formation of the composite and enhanced visible-light absorption with improved charge separation efficiency. Among the prepared samples, the photocatalyst containing 30 wt% AgCl exhibited the best performance, achieving approximately 80% OFL removal within 180 min under visible-light irradiation. The degradation followed pseudo-first-order kinetics with a rate constant of 0.0155 1/min, which was significantly higher than those of pure ZnO and AgCl. Operational parameters were systematically evaluated, revealing that an OFL concentration of 10 mg/L, catalyst dosage of 0.2 g/L, reaction temperature of 45 °C, and acidic conditions (pH 3.4) provided optimal degradation efficiency. Radical scavenging experiments demonstrated that superoxide radicals (·O₂⁻) were the dominant reactive species, while the enhanced activity was attributed to efficient interfacial charge transfer across the AgCl/ZnO heterojunction and the superior adsorption capability of ZnO. A plausible degradation pathway was proposed, indicating the fragmentation and eventual mineralization of OFL into smaller molecules. These findings highlight the strong potential of AgCl/ZnO composites as efficient visible-light photocatalysts for the removal of antibiotic pollutants from water.