Sunlight driven photocatalytic degradation of ciprofloxacin over a dual S-scheme based BiOCl/Bi2WO6/g-C3N4 ternary heterojunction.

The contamination of fluoroquinolone antibiotics in wastewater, particularly ciprofloxacin (CIP), poses significant environmental and health hazards, as these are resistant to conventional treatment methods. In the current study, a highly effective dual S-Scheme-based heterojunction photocatalyst, comprising BiOCl, Bi2WO6, and g-C3N4, was designed via a simple hydrothermal method. The developed material was comprehensively characterized using various physicochemical techniques such as XRD, FTIR, FESEM, HRTEM, XPS, N2 sorption analysis, TGA, DR UV-vis, and PL, confirming the successful assembly of a well-integrated nanostructure with an optimised band configuration favourable for visible-light absorption. Under sunlight exposure, the BiOCl/Bi2WO6/g-C3N4 heterojunction (BWC) demonstrated excellent photocatalytic activity, achieving 96% degradation of CIP within 90 min, outperforming the individual components. The outstanding activity was ascribed to the cooperative effect of dual S-Scheme charge transfer, which enhanced charge separation and preserved their strong redox abilities. Heterogeneity and reusability studies were performed, and the developed catalyst showed excellent stability up to the fifth run with consistent performance. Kinetic study showed a first-order degradation pattern, while radical trapping tests detected superoxide radicals as the major reactive oxygen species. Based on fragments obtained from LCMS analysis, a plausible mechanism of CIP degradation was established.