Er-doped g-C3N4 for photodegradation of tetracycline and tylosin: High photocatalytic activity and low leaching toxicity

Through direct thermal condensation of a mixture of Er(NO 3 ) 3 ·5H 2 O and melamine at 550 °C for 2 h, a series of rare earth agent Er (III)-doped mesoporous g-C 3 N 4 (xECN, x = 1,2,3) with different Er content were successfully synthesized. XRD, solid-state 13 C CP/MAS, FT-IR, XPS, UV–Vis DRS, photocurrent, EIS, SEM, TEM, BET and Zeta potentials were used to characterize the phase, morphology, optical and surface properties of xECN photocatalysts. The photo-activities of xECN samples for degradation of Rhodamine B (RhB), tylosin (TYL) and tetracycline (TC) were enhanced compared with those of pure g-C 3 N 4 under the irradiation of simulated solar, and the 2ECN catalyst displayed the optimal degradation rate for all three organic pollutants. The UV–vis results demonstrated that Er doping narrowed the band gap while increasing the light harvesting ability, which improved the photocatalytic activity of g-C 3 N 4 catalyst. The leaching and toxicity tests were conducted with pakchoi seeds and Escherichia coli bacteria, demonstrating that the leaching toxicity of xECN could be ignored. Free radical capture tests were carried out to confirm the main active species for the degradation of RhB under the same experimental condition.