Nano-magnetite supported by biochar pyrolyzed at different temperatures as hydrogen peroxide activator: Synthesis mechanism and the effects on ethylbenzene removal

Abstract Nano-magnetite supported by biochar (nFe3O4/BC) pyrolyzed at temperatures of 300 °C to 600 °C was developed to activate hydrogen peroxide (H2O2) for the efficient degradation of ethylbenzene in aqueous solution. It was revealed that the degradation efficiency of ethylbenzene and TOC removal were 96.9% and 36.2% respectively after the reaction for 40 min in the presence of initial concentration of 0.1 mmol L-1 ethylbenzene, 2.76 g L-1 nFe3O4/BC500 with the mass ratio of nFe3O4 to BC500 of 4:1 and 2.0 mmol L-1 H2O2 at pH 7.0. Based on electron paramagnetic resonance (EPR), quenching experiment and X-ray photoelectron spectroscopy (XPS) data, both •OH and O2•- radicals were generated in the nFe3O4/BC500 activated H2O2 system, and the •OH radicals were the predominant species for the degradation of ethylbenzene. Through electron transfer process, mechanisms of Fe(II), phenolic hydroxyl group and persistent free radicals (PFRs) on BC surfaces accounted for the generation of •OH radicals, and Fe(III) in nFe3O4 and formed from Fe(II) oxidation responsible for the generation of O2•- radicals in the nFe3O4/BC activated H2O2 system were proposed.