Enhanced aquatic antibiotic removal via dual piezoelectric photocatalyst CdS/BiFeO3 S-scheme heterojunction: Mechanism, degradation pathway, and toxicity evaluation

Piezo-photocatalysis represents an effective and eco-friendly strategy for water purification, wherein singlet oxygen (¹O₂) serves as a crucial reactive oxygen species due to its exceptional selectivity and remarkable oxidative capacity in wastewater degradation processes. Herein, we elaborately designed a dual piezoelectric photocatalyst, the Cadmium sulfide/Bismuth ferrite (CdS/BiFeO₃) step-scheme (S-scheme) heterojunction to synergistically enhance generation pathways of ¹O₂ for efficient removal of antibiotic contaminants. In this study, under the combination of ultrasonic vibration and visible light irradiation, the optimized CdS/BiFeO₃-10 % exhibited a reaction rate constant of 0.200 min⁻¹ for ciprofloxacin (CIP) degradation, which was 9.52 and 5.88 times higher than that of individual piezocatalysis and photocatalysis, respectively. The synergistic effect of the interfacial electric field and the vibration-induced piezoelectric field significantly promoted charge carrier separation, as supported by detailed experimental and theoretical results. Through quenching experiment and Electron spin resonance (ESR), ¹O₂ and holes (h⁺) played major roles in CIP degradation. Furthermore, the toxicity and degradation pathways of CIP intermediates were systematically evaluated. The CdS/BiFeO₃ composite also demonstrated outstanding reusability and cycle stability, making it suitable for practical wastewater treatment applications. This work highlights the potential of CdS/BiFeO₃ with piezoelectric effect-assisted S-scheme heterojunction for highly efficient antibiotic wastewater remediation, offering a novel and effective strategy for water purification.