| The problem of antibiotic pollution is becoming more and more serious, and the abuse of tetracycline leads to its residue in the water area, which poses a potential threat to the natural environment and human health. Therefore, it is of high application value to study how to degrade tetracycline in wastewater. Photocatalysis is an ideal method for tetracycline degradation in wastewater because of its green, high efficiency and energy saving. Graphite phase carbon nitride (g-C3N4) is a good nonmetallic photocatalyst, but its photocatalytic performance is affected by the limited absorption of visible light and the rapid recombination of photogenerated electron holes. In order to improve photo response and charge separation, PDIN/g-C3N4 composite photocatalyst was prepared by hydrothermal method. The photocatalytic degradation efficiencies of tetracycline were studied by combining PDIN/g-C3N4 in different proportions. The experiment of photocatalytic degradation of tetracycline showed that g-C3N4-20 composite had the highest photocatalytic degradation efficiency, and the degradation rate constant was 0.0052 min-1. The photocatalytic degradation efficiency of tetracycline was different with different amount of catalyst, and the degradation kinetics curves were consistent with first-order reaction kinetics. The surface morphology and functional groups of the samples were analyzed by scanning electron microscopy and Fourier infrared spectroscopy. Ultraviolet-visible diffuse reflectance analysis showed that the introduction of PDIN improved the visible light absorption capacity of g-C3N4, and the charge transfer behavior inside the photocatalyst was analyzed by means of steady-state fluorescence spectroscopy. The results of electrochemical impedance spectroscopy show that the composite can promote the separation of photogenerated electron-hole pairs effectively. Therefore, the main reason for the improvement of the performance of the composite photocatalyst is that PDIN forms a heterojunction with g-C3N4 through π-π packing interaction, which promotes the photogenerated charge transfer process, and promotes the photocatalytic degradation of tetracycline together with effective visible light absorption. The quenching experiments show that the main active substances of tetracycline degradation by composite photocatalyst are ?O-2 and?OH. The PDIN/g-C3N4 composite photocatalyst successfully synthesized in this paper significantly improves the degradation effect of tetracycline, and provides a new idea and method for the treatment of tetracycline wastewater, which has important theoretical and practical application value. |
