A pH-tolerant self-Fenton system with excellent antibiotics degradation performance over sulfonated g-C3N4 composite hematite photocatalyst

Photocatalytic self-Fenton technology can effectively purify antibiotic-contaminated water through an in-situ H2O2 synthesis and activation process. However, variations in acidity or alkalinity of wastewater can significantly impact the H2O2 synthesis and activation performance, making it necessary to expand the working pH range of the self-Fenton system. Herein, we construct a pH-tolerant self-Fenton photocatalyst (hematite/HSCN) by using grafted amino sulfonic to modulate the surface structure of g-C3N4 and loading of hematite to activate H2O2. Our findings reveal that sulfonated g-C3N4 (HSCN) exhibits enhanced proton capture capability, ensuring a stable proton supply during H2O2 synthesis under varying acidity or alkalinity conditions. Compared to g-C3N4, HSCN exhibits up to a 59.8-fold enhancement in H2O2 synthesis, maintaining high efficiency even under neutral and weak alkaline conditions. Furthermore, the loaded hematite nanoparticles effectively activate H2O2 in situ, enabling hematite/HSCN to degrade ibuprofen and tetracycline. Toxicity analysis shows a gradual reduction of pollutants toxicity during degradation, ultimately achieving mineralization and water purification. This study extends the working pH range of the photocatalytic self-Fenton system by enhancing the proton capture capability of the catalyst, providing a new insight for promoting the role of photocatalytic self-Fenton systems in environmental protection.