Enhanced degradation of ofloxacin by activation of peroxymonosulfate with biochar-FeVO4 under visible light assistance: The role of biochar in mediating charge transfer and mechanism insight

Abstract

Biochar is recognized as a good medium for promoting photogenerated charge separation in photocatalysts. In this study, the FeVO4/coconut shell biochar (CSB) composites (FVC) were prepared through a cost-effective hydrothermal approach to activate peroxymonosulfate (PMS) for the degradation of ofloxacin (OFX). Incorporated CSB expanded the light absorption range of FVC by approximately 100 nm, and the band gap energy of FVC was reduced to 2.00 eV. Measurements through linear scanning voltammetry (LSV) and current–time (IT) chronoamperometric further confirmed that the accelerated electron transmission rate boosted PMS oxidation, which was attributed to the role of CSB acting as a mediator. Importantly, OFX degradation was significantly boosted by CSB, FV, and PMS synergistically. FVC had a significant OFX degradation efficiency under visible light irradiation (95.2 %) compared to FV (70.9 %), CSB (57.8 %) and PMS (30.5 %). Moreover, the h+, 1O2, ·O2–, ·OH, and SO4·− were the main active species, whose degradation pathways were explored and the toxicity of the intermediates was assessed. Furthermore, the as-obtained FVC exhibited a remarkable stability and reusability. This work provides new insights into the mechanism of biochar-mediated charge transfer for antibiotic degradation.