Efficiently enhanced visible-light photocatalytic activity by in situ deposition of Ag@AgBr on g-C₃N₄/Fe₃O₄ magnetic heterogeneous materials

In this study, graphitic carbon nitride (g-C₃N₄) (CN) was conveniently and environmentally modified into a stable and easily recyclable photocatalyst for the high removal efficiency of dye contaminants in water. Magnetic carrier (CN/Fe₃O₄) and heterojunction photocatalysts (Ag@AgBr/CN/Fe₃O₄) were prepared by ultrasonic and in situ deposition of Fe₃O₄ and Ag@AgBr nanoparticles on the CN, respectively, and characterized by the surface structure, optical, and electrochemical properties. The effects of different catalysts, silver loading, catalyst dosage, and different aeration conditions on the photocatalytic degradation of RhB were investigated. Results exhibited that the removal rate of RhB by Ag@AgBr/CN/Fe₃O₄ reached 96% within 150 min when the Ag loading was 5%, the catalyst dosage was 0.4 g/L, and the aeration was air. Furthermore, the degradation rate constant was 17.3 × 10⁻³ min⁻¹, which was 4.3 and 3.4 times higher than that of CN and CN/Fe₃O₄, respectively. The stability study demonstrated that Ag@AgBr/CN/Fe₃O₄ had almost no risk of Ag and Fe leakage and showed high stability. Mechanism study indicated that the construction of Z-scheme heterojunction between Ag@AgBr and CN and trapping electron by Fe³⁺ promoted charge transfer and electron–hole pair separation, thus enhancing photocatalytic activity.