Photocatalytic Estrogen Degradation by the Composite of Tin Oxide Fine Particles and Graphene-like Carbon Nitride

• Published in: ACS omega 2024-12, Vol.9 (50), p.49064-49070
• Main Authors: Amino, Yuzuki, Al-zubaidi, Ayar, Ishii, Yosuke, Kawasaki, Shinji
• Format: Article
• Language: English
• ISSN: 2470-1343; 2470-1343
• DOI: 10.1021/acsomega.4c03390

This study investigates whether 17β-estradiol (E2), a natural estrogen and one of the endocrine-disrupting chemicals responsible for water pollution, can be oxidatively decomposed under simulated solar light using a composite of tin oxide nanoparticles and graphene-like carbon nitride (g-CN) as a photocatalyst. The composite photocatalyst was prepared by heating a mixture of urea and tin acetate. FT-IR measurements revealed that g-CN possesses structural units similar to g-C3N4, a well-studied graphite-like carbon nitride. However, unlike g-C3N4, sharp diffraction lines were not observed in the XRD diffraction pattern of g-CN, indicating lower crystallinity. Elemental analysis showed that g-CN is slightly nitrogen-rich compared to g-C3N4, and UV–vis measurements indicated that the band gap of g-CN is slightly smaller than that of g-C3N4. The presence of tin in the composite of tin oxide and g-CN was clearly confirmed by XPS, although no sharp diffraction peaks were observed in the XRD patterns, suggesting the presence of microcrystals. Furthermore, FE-SEM observations did not reveal large tin oxide crystals, although EDS mapping indicated the presence of tin oxide. It was found that the prepared tin oxide and g-CN composites function effectively as photocatalysts for degrading E2 under simulated solar light. The degradation rate constant was evaluated to be k = 3.34 (0.14) × 10–2 min–1. Peroxide ion radicals were detected in ESR measurements from the irradiated solution, suggesting that peroxide ion radicals are generated through oxygen photoreduction as the counter-reaction of the oxidative decomposition of E2.