Triggering sustainable regeneration of Fe2+ by S-scheme Bi2Fe4O9/BiOBr heterojunction toward highly efficient peroxymonosulfate activation for visible-light-driven removal of thiabendazole

Abstract

Peroxymonosulfate (PMS)-assisted photocatalytic processes are economical and green strategies for the treatment of pesticide pollution. However, its degradation efficiency is severely hindered by the sluggish kinetics of active centers regeneration and low charge-transfer. Herein, S-scheme Bi2Fe4O9/BiOBr heterogeneous material was designed to activate PMS for thiabendazole (TBZ) degradation. Bi2Fe4O9 and BiOBr have similar structural unit of [Bi2O2]2+ to share the Bi-O bonds, which is favorable to form asymmetric interface and enhance the polarization. Based on these unique characteristics between Bi2Fe4O9 and BiOBr, a robust internal electric field in the S-scheme heterojunction is built, which could provide driving force to boost the electron-transfer process and encourage the sustainable regeneration of Fe2+. After optimizing the proportion of Bi2Fe4O9 on the composite, it was found that 50 wt% Bi2Fe4O9/BiOBr (BFB-50) exhibits the best TBZ removal efficiency after 30 min visible light irradiation, which is 2.25 and 12 folds compared to Bi2Fe4O9 and BiOBr, respectively. Furthermore, electron paramagnetic resonance (EPR) and radical trapping experiments indicate that 1O2 and SO4•- involving oxidation mechanism impart maximum contribution towards TBZ degradation. The possible pathways of TBZ degradation are reasonably proposed by the HPLC-MS and the toxicity evolution of TBZ is appraised using the ECOSAR software. This study provides an insight into the fabrication of S-scheme heterojunction for environment remediation through the photocatalysis/sulfate-mediated advanced oxidation process.