In-situ fabrication of Bi2O3/g-C3N4/sepiolite photocatalyst for tetracycline degradation under visible light: Performance, mechanism and degradation pathways

In this study, the ternary Bi₂O₃/g-C₃N₄/sepiolite composite with excellent photocatalytic activity was prepared via hydrolysis precipitation and calcination procedure. The Bi₂O₃/g-C₃N₄/sepiolite photocatalyst performed dramatically improved visible-light-driven photodegradation efficiency for tetracycline (TC) within 3 h (91.71 %), which was almost 2.24, 6.5, 1.28, 1.36 1.76 times that those of Bi₂O₃, g-C₃N₄, g-C₃N₄/sepiolite, Bi₂O₃/sepiolite and Bi₂O₃/g-C₃N₄, respectively. The results demonstrated that there was a synergistic effect among the components of the ternary composite, which effectively promoted the separation and transfer of photoinduced electron-hole pairs. The role of sepiolite was particularly important as a carrier of Bi₂O₃/g-C₃N₄ heterojunction, providing more reaction active sites and better electron transport path. The quenching experiment showed that O₂^•- were the main active species during TC degradation process. Furthermore, the photocatalytic degradation mechanisms and possible degradation pathways of TC were also investigated. This work provides new ideas for the mineral-based ternary photocatalytic composites to degrade pollutants in wastewater.