Accelerate the Photo-Induced Fe 2+ /Fe 3+  Cycle in Bi 24 Fe 2 O 39 -H 2 O 2  System by Mn Doping for Tetracycline Degradation

Abstract

The heterogeneous photo-Fenton synergistic reaction has emerged as a promising technique for organic pollutant degradation in water, owing to its efficient utilization of solar energy to facilitate the reduction of Fe³⁺ to Fe²⁺, thereby enabling the continuous generation of reactive oxygen species (ROSs) result in efficient degradation of pollutants. Herein, a heterogeneous photo-Fenton catalyst, Mn/Bi24Fe2O39, is fabricated via a sol-gel calcination method. The Mn/Bi24Fe2O39 (k=0.01 min-1) displays 3.3-fold higher degradation rate than pristine Bi24Fe2O39 (k=0.0031 min-1) for tetracycline degradation. A remarkable improvement in the degradation rate of Mn/Bi24Fe2O39 derives from increasement the absorption of visible light, the formation of inter-band energy levels, the effective separation and transmission of photogenerated carriers through Mn-O-Fe, which are in favour of the redox cyclic of Fe2+/Fe3+ and continuous generation of ROSs. In addition, with the help of liquid chromatography-mass spectrometry (LC-MS), ROSs induced three specific degradation pathways of tetracycline is proposed, including dehydroxylation, decarboxylation, demethylation, ring opening and deamidation, etc. The study provides a unique insight for enhancement of Fe2+/Fe3+ cycle and broadens the application of bismuth ferrite materials in the field of environmental remediation.

Keywords: Photo-Fenton, Bismuth ferrite, Charge separation, Antibiotics degradation