Enhanced visible light photo-Fenton-like degradation of tetracyclines by expanded perlite supported FeMoO/g-CN floating Z-scheme catalyst.

In the conventional Fenton system, the relatively low efficiency of Fe (II) regeneration is a significant drawback. To address this shortcoming, a novel floating Z-scheme photo-Fenton catalyst FeMoO/g-CN/EP was prepared by a facile dip-calcination method, in which iron and molybdenum oxides with mixed valence states (FeMoO) and graphitic carbon nitride (g-CN) were loaded on the expanded perlite. The removal efficiencies reached the maximum at 98.0%, 93.1% and 97.1% for tetracycline, oxytetracycline and chlortetracycline, respectively, after 60 min dark adsorption and 60 min photo-Fenton process. The aid of dual ion (Fe and Mo) synergy system and photoreduction by Z-scheme photocatalyst enhanced the Fe (II) regeneration, resulting in the excellent performance. Radical scavenger experiment, electron spin resonance spectra (ESR) and X-ray photoelectron spectra (XPS) were used to confirm the mechanism of free radicals' formation and Fe/Mo redox cycling. ·OH, ·O and O played important roles in the pollutant's degradation, while the generation of ·O was enhanced due to the floatability in this system. The possible degradation pathways of TC were put forward according to the results of mass spectrum and Orbital-Weighted Fukui Function. Overall, this work provides new insights on the cooperation between iron-based mix oxides and semiconductor in the photo-Fenton system.