Enhanced Sulfamerazine Removal via Adsorption–Photocatalysis Using Bi2O3–TiO2/PAC Ternary Nanoparticles

The presence of sulfonamides (SAs) in water has received increasing attention due to the risk to ecosystems. The adsorption and photocatalysis performance for sulfamerazine (SMZ) of Bi2O3–TiO2 supported on powdered activated carbon (Bi2O3–TiO2/PAC) nanoparticles was evaluated. The amount of doped Bi2O3 not only influenced the photocatalytic performance but also impacted the adsorption capacity. The adsorption mass transfer mechanism of Bi2O3–TiO2/PAC was elucidated and is further discussed in combination with the photocatalytic mechanism. It was indicated that Bi2O3–TiO2/PAC(10%–700 °C) performed best, and the SMZ removal by the adsorption–photocatalysis of Bi2O3–TiO2/PAC(10%–700 °C) reached 95.5%. Adsorption onto active sites was a major adsorption step, and external diffusion was assisted. Superoxide radical (●O2−) and hole (h+) were identified as the major reactive oxygen species (ROS) for SMZ removal. Benzene ring fracture, SO2 extrusion and nitrogenated SMZ were proposed as the main pathways for photocatalysis. Meanwhile, alkaline conditions enhanced photocatalytic performance, while contrary effects were observed for adsorption. The adsorption–photocatalysis removal performance for SMZ in lake water was better than that for river water. It can be generalized for the potential application of photocatalysis coupling with adsorption to remove refractory antibiotics in water.