By using melamine as a precursor for the copolymerization process, g-C3N4 and g-C3N4/TCNQ/Eu complexes with various amounts of doping were created. These complexes were then examined using XRD, FT-IR, SEM, TEM, XPS, PL, UV-vis, and I-T. The degradation rates of pefloxacin (PEF), enrofloxacin (ENR), and ciprofloxacin (CIP) were 91.1%, 90.8%, and 93.2% under visible light (λ > 550 nm). The photocatalytic performance of the composite was analyzed, and the best effect was obtained for CIP photocatalysis when Eu doping was 3 mg at 20 °C and pH 7. Kinetic analysis showed that there was a linear relationship between the sample and the photocatalytic time, and the degradation rate was about 5 times that of g-C3N4. The cyclic stability of the g-C3N4/TCNQ/Eu composite sample was found to be good through repeated experiments. UPLC-MS visualizes the degradation process of CIP. The extremely low stability of piperazine ring induced subsequent degradation, followed by the fracture of quinolone ring promoting the complete decomposition of CIP.
Keywords: antibiotics; degradation pathway; photocatalytic degradation.