Water flow-driven N-CQDS/MoS2 piezoelectric-photocatalytic percarbonate degradation of oxytetracycline: response surface modeling and mechanistic analysis

To overcome the limitations of high energy consumption and low selectivity in conventional antibiotic treatment methods, this study developed a sodium percarbonate (SPC)-activated piezoelectric-photocatalytic system using a nitrogen-doped carbon quantum dot/molybdenum disulfide (N-CQDs/MoS₂) composite to degrade oxytetracycline (OTC). The catalyst was synthesized via a hydrothermal method and characterized by X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), piezoresponse force microscopy (PFM), and electrochemical analysis. Results showed that nitrogen-doped carbon quantum dots significantly enhanced the piezoelectric and photocatalytic performance of MoS₂. Reaction conditions were optimized using response surface methodology (RSM), determining the optimal parameters as OTC concentration of 10.68   mg/L, catalyst dosage of 0.46   g/L, and SPC dosage of 0.21   g/L. Under these conditions, a degradation efficiency of 99.52% was achieved within 25   minutes, closely matching the experimental result of 99.18%. The degradation kinetics followed a quasi-first-order model (k = 0.0752   min⁻¹), confirming the model’s reliability. Radical scavenging experiments and electron paramagnetic resonance (EPR) analysis identified h⁺, •OH, and O₂•⁻ as the main reactive species. Ecotoxicity assessment showed low toxicity of the degradation products, indicating good environmental safety. The catalyst maintained a high degradation efficiency of 96% after five cycles, demonstrating excellent stability and reusability.