Photo-Fenton degradation of oxytetracycline by g-C3N4/CQDs/FeOCl with in-situ hydrogen peroxide production: Degradation pathway and toxicity analysis of intermediate products

Abstract

Heterogeneous photocatalytic Fenton technology, as an advanced oxidation process (AOPs), is considered a promising method for treating antibiotic wastewater. In the article, a heterogeneous photo-Fenton system g-C₃N₄/CQD/FeOCl with in-situ H₂O₂ production was constructed and used for photo-Fenton degradation of oxytetracycline (OTC). The successful preparation of Z-scheme heterojunction photocatalyst g-C₃N₄/CQDs/FeOCl was proved by a series of characterizations. The optimal degradation efficiency of OTC could reach as high as 96 %, basically achieving the effect of traditional Fenton reaction. Importantly, the degradation mechanism result demonstrated that ^•OH was the most active species for the degradation of OTC, and most of it were generated by the Fenton reaction within the constructed system. In addition, the main degradation pathways of OTC were detected by liquid chromatography-mass spectrometry. The three-dimensional fluorescence and toxicity analysis of the intermediate products showed that OTC was decomposed into intermediate products with smaller molecular weight, and the biological toxicity was reduced. This study provides new ideas for improving the application of Fenton reaction in wastewater treatment.