Efficient photocatalytic degradation of tetracycline under visible light by AgCl/Bi12O15Cl6/g-C3N4 with a dual electron transfer mechanism

Abstract

A novel and efficient ternary composite AgCl/Bi12O15Cl6/g-C3N4 photocatalyst was prepared by co-precipitation method. The physical structure and photochemical properties of the photocatalyst were analyzed by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Ultraviolet diffuse reflectance spectroscopy (UV-DRS), Fluorescence spectroscopy (PL). The performance of the prepared photocatalysts was evaluated by performing degradation experiments of tetracycline (TC) under different conditions (doping ratio, dosage, initial concentration and initial pH of solution). Furthermore, the stability of composite was confirmed by cycling experiment. Finally, the mechanism of ternary composite AgCl/Bi12O15Cl6/g-C3N4 photocatalyst for decomposition of TC in visible light was investigated by free radical capture experiment. The photoluminescence spectra showed that the peak intensity of the AgCl/Bi12O15Cl6/g-C3N4 composite was significantly reduced compared to other materials, indicating that the photogenerated electron-hole pairs were effectively separated, which contributed to its photocatalytic activity. The composite showed higher TC degradation activity compared to g-C3N4, Bi12O15Cl6/g-C3N4 and AgCl/g-C3N4, with optimum degradation rate constants of 8.2, 2.2 and 1.6 times that of g-C3N4, Bi12O15Cl6/g-C3N4 and AgCl/g-C3N4, respectively. Furthermore, based on the free radical capture experiment, it was confirmed that the active species playing a major role in the reaction process were·O2-, followed by h+ and·OH. A double electron transfer mechanism was inferred to be formed in the AgCl/Bi12O15Cl6/g-C3N4 composite and a possible pathway for the degradation of TC was postulated. This work provides a new approach for the effective use of solar energy, as well as a new solution strategy for the degradation of TC in wastewater.