Fabrication of flower-globular Bi2WO6/BiOI@Ag3PO4 photocatalyst for the degradation of bisphenol A and cefepime under sunlight: Photoelectric properties, degradation performance, mechanism and biodegradability enhancement

A flower-globular photocatalyst (Bi2WO6/BiOI@Ag3PO4-5) with symmetric double-heterojunction structure and low Ag-content was successfully fabricated for the first time by precipitation and one-step hydrothermal process. The loading of Ag3PO4 evidently enhanced the photoelectric properties of photocatalysts. Bi2WO6/BiO-I@Ag3PO4-5 provided an ideal photocatalytic activity towards the degradation of bisphenol A (BPA) and cefepime under simulated sunlight, and it also exhibited well photocatalytic stability. For BPA degradation, the recommend photocatalyst provided nearly 100% of degradation efficiency and 65.4% TOC removal by the simulated sunlight irradiation of 120 min, while for cefepime degradation, it offered the degradation efficiency of 98.2% and the TOC removal efficiency of 33.4%. The mechanism of photocatalytic activity enhancement was owing to the loading of Ag3Po4 and the developed double-heterojunction structure, by which the absorbance of visible light, the separation of electron/hole (e(-)/h(+)) pairs and carrier mobility were enhanced evidently. It was found that superoxide anion radical (center dot O-2(-)) played the major role in BPA degradation, while hydroxyl radical (center dot OH) and hole (h(+)) together played the key role in cefepime degradation. The two pathways for BPA and cefepime degradation were respectively proposed by identifying the byproducts formed during the degradation. In addition, it was found that the photocatalytic degradation of cefepime evidently enhanced the biodegradability of the solution.