Rapid visible-light degradation of EE2 and its estrogenicity in hospital wastewater by crystalline promoted g-C3N4

Abstract

Metal-free, chemically activated crystalline graphitic carbon nitride (g-C3N4) nanorods with enhanced visible-light photoactivity demonstrated rapid photodegradation of 17α-ethinylestradiol (EE2) in water and real hospital wastewater. Pure g-C3N4 and another three crystalline promoted g-C3N4 photocatalysts developed by hydrothermal method were characterized by, High-Resolution Transmission Electron Microscopy (HRTEM), X-ray diffraction (XRD), Fourier-Transform Infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), Photoluminescence (PL), Electron spin resonance (ESR), X-ray Photoelectron Spectroscopy (XPS) and Diffuse Reflectance Spectroscopy (DRS). Hydrothermal-based chemical activation did not alter the crystal structure, functional group or surface morphology, but it enhanced the specific surface area of activated g-C3N4 due to intralayer delamination and depolymerization of g-C3N4. Compared to pure g-C3N4, the activated g-C3N4-3 demonstrated efficient degradation of EE2 (<30 min, 3 mg/l) by visible wavelengths of the solar spectrum. This work provides advanced insight into the construction of heterojunction visible-light photocatalysts and production of O2− via reduction of O2 with photogenerated electrons. Proposed and derived mechanism for photodegradation of EE2 by g-C3N4-3 using gas chromatography-mass spectrometry (GCMS). Yeast Estrogen Screen (YES) was performed to evaluate the estrogenicity of treated water samples. Efficient removal of EE2 estrogenic activity (<45 min, 3 mg/l) was achieved using the visible light-activated g-C3N4. Estrogenicity removal rate corresponded well with EE2-degradation rate.