Enhanced visible light photo-Fenton-like degradation of tetracyclines by expanded perlite supported FeMo3Ox/g-C3N4 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 FeMo3Ox/g-C3N4/EP was prepared by a facile dip-calcination method, in which iron and molybdenum oxides with mixed valence states (FeMo3Ox) and graphitic carbon nitride (g-C3N4) 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. center dot OH, center dot O2- and 1O2 played important roles in the pollutant's degradation, while the generation of center dot O2- 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.

Automated summary

A novel floating Z-scheme photo-Fenton catalyst FeMo3Ox/g-C3N4/EP was prepared to address the low efficiency of Fe (II) regeneration in the conventional Fenton system. The dual ion synergy system and photoreduction by Z-scheme photocatalyst enhanced the Fe (II) regeneration, leading to excellent pollutant degradation efficiency. Radical scavenger experiment, ESR, and XPS were used to confirm the mechanism of free radicals' formation and Fe/Mo redox cycling, while mass spectrum analysis and Orbital-Weighted Fukui Function revealed the possible degradation pathways of the pollutants.