Enhanced Heterogeneous Photo-Fenton Catalytic Degradation of Tetracycline over yCeO2/Fh Composites: Performance, Degradation Pathways, Fe2+ Regeneration and Mechanism

Abstract Natural ferrihydrites (Fh) can activate H2O2 to produce reactive oxygen species in Fenton-like system, while the inefficient Fe2+ regeneration limited its application. A novel heterogeneous photo-Fenton catalyst with enhanced organics degradation activity was developed by decorating bio-template synthesized ceria (yCeO2) on Fh (yCeO2/Fh). Various characterizations (i.e., XRD, SEM-EDS, FT-IR, XPS and DRS) for the prepared yCeO2/Fh verified the location of yCeO2 on Fh surface and the semiconductive properties of yCeO2. Different influential reaction parameters were thoroughly explored and the 15-yCeO2/Fh composite with 15% mass ratio of yCeO2 showed significantly enhanced degradation rate (98.7%) and mineralization rate (70.1%) of tetracycline (TC) than pure Fh. Three plausible TC degradation pathways were proposed on account of the emerging intermediates identified by LC-MS. The co-existing anions that mildly inhibited TC catalytic degradation have closely relation to TC removal efficiency in tap water and river water. Mechanism analyses confirmed the appropriate yCeO2 introduction accelerated Fe2+ and Ce3+ regeneration with assistant of photo-electrons and Ce4+/Ce3+ circulation, which further facilitated H2O2 consumption and resulted in higher TC degradation efficiency. Radicals trapping experiments and electron spin resonance measurement proved that •OH played critical contribution in organics degradation. When the catalysts were employed to other types pollutants such as Tetrabromobisphenol A, Rhodamine B and 2,4-dichlorophenol, yCeO2/Fh composite still showed excellent catalytic activity. Therefore, this study provides insight into the yCeO2 action in minerals/photo-Fenton catalytic system and further broadens the development of visible-light-response catalysts application in Fenton-like system.