Performance and mechanism of efficient degradation of diethylenetriamine (DETA) in water by UV/g-C3N4@BiOI/H2O2 system

Heterojunction-structured graphitic carbon nitride@bismuth oxyiodide (g-C 3 N 4 @BiOI) nanocomposites were successfully synthesized via a facile solvothermal method. The as-prepared composites were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and UV–visible diffuse reflectance spectroscopy (UV–vis DRS) to elucidate their microstructure, chemical composition, and optical properties. Subsequently, a highly efficient UV/g-C₃N₄@BiOI/H₂O₂ photocatalytic system was developed for the rapid degradation of diethylenetriamine (DETA). Under optimal conditions (initial pH 10.3, 0.4 mL/L H₂O₂, and 0.06 g/L 50 wt% g-C₃N₄@BiOI), the system achieved 95% DETA removal within 30 min under UV irradiation. Notably, cyclic degradation tests coupled with post-characterization revealed the exceptional stability and reusability of the g-C₃N₄@BiOI nanocomposite. Mechanistic studies through radical quenching experiments and electron paramagnetic resonance (EPR) spectroscopy confirmed •OH as the primary reactive species. Furthermore, the degradation pathways were elucidated by combining Gaussian 09 W theoretical calculations with gas chromatography–mass spectrometry (GC–MS) analysis. Finally, the toxicity evaluation model was established by toxicity evaluation software, and the experiments of mung bean germination and zebra fish egg incubation verified the effective detoxification of DETA solution after photocatalytic treatment.