S-scheme ZnMn2O4/V2O5 heterojunction for degradation of ciprofloxacin hydrochloride under visible-light irradiation

To address the inherent limitations of V ₂ O ₅ (VO) photocatalysts, such as high photogenerated electron-hole pair (PEHP) recombination rate and susceptibility to photocorrosion, the S-scheme ZnMn ₂ O ₄ /V ₂ O ₅ (ZMO/VO) heterojunction materials were successfully synthesized by loading ZnMn ₂ O ₄ (ZMO) on the VO surface via the hydrothermal method. Through crystal structure characterization, it was found that the prepared ZMO/VO composite retained the main structure of the orthorhombic system of VO, and the introduction of ZMO did not significantly change the crystalline characteristics of VO. Microstructural characterization revealed that ZMO was uniformly and densely dispersed on the VO surface, effectively enhancing the catalyst's surface roughness and specific surface area while establishing an efficient S-scheme heterojunction structure at the interface between the two catalytic materials. This unique structural design optimizes the interfacial charge transport path while preserving highly active REDOX sites, which significantly improves the catalytic performance of the material under visible light. The photocatalytic degradation mechanism of ciprofloxacin hydrochloride (CIP) revealed that superoxide radicals (·O ₂ ⁻ ) and hydroxyl radicals (·OH) served as the predominant reactive oxygen species responsible for CIP decomposition. When the ZMO loading was 6 wt%, the composite showed the best catalytic performance. Under the conditions of a catalyst dosage of 0.4 g/L, an initial CIP concentration of 20 mg/L, and pH = 6, a degradation rate of 98.7% could be achieved after 100 minutes of visible light irradiation. Notably, the material also showed good stability, maintaining a degradation efficiency of 91.6% after four cycles of use. This study offers an effective strategy to address the intrinsic limitations of VO-based photocatalysts while simultaneously advancing the rational design of S-scheme heterojunction materials for practical environmental remediation applications.