Design and Synthesis of an Asymmetric Graphitic Carbon Nitride Photocatalyst for Visible-Light-Driven Degradation of Pharmaceutical Pollutants: Structural Engineering, Optimization, and Mechanistic Insights

An asymmetric graphitic carbon nitride (g-CN)-based photocatalyst was designed and synthesized for the simultaneous removal of the environmentally persistent pharmaceutical contaminants acetaminophen and metronidazole. Graphitic carbon nitride was initially prepared via thermal polymerization, and its structure was subsequently modified through structural engineering and controlled soft lattice distortion to obtain asymmetric graphitic carbon nitride (ACN) with enhanced photocatalytic performance. The structural, morphological, optical, and electrochemical properties of BCN and ACN were systematically characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field-emission scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (FE-SEM/EDS), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), photoluminescence (PL) spectroscopy, chronoamperometry, and electrochemical impedance spectroscopy (EIS). The results confirmed that the asymmetric structural modification enhanced visible-light absorption, narrowed the band gap from approximately ۲.۸۹ to ۲.۷۸ eV, suppressed the recombination of photogenerated electron-hole pairs, and promoted interfacial charge-transfer efficiency. The photocatalytic activity of ACN toward the degradation of acetaminophen and metronidazole, both individually and in a binary system, was evaluated under visible-light irradiation using central composite design (CCD) combined with response surface methodology (RSM). Moreover, the degradation kinetics were well described by the Langmuir-Hinshelwood model. The satisfactory stability and reusability of ACN further highlight its potential as an efficient photocatalyst for the treatment of pharmaceutical-contaminated water.

کلیدواژه ها:

Photocatalytic degradation ، Acetaminophen ، Metronidazole ، Pharmaceutical contaminants ، Visible-light photocatalysis ، Response surface methodology (RSM) ، Water treatment