Degradation of methyl orange through hydroxyl radical generated by optically excited biochar: Performance and mechanism

Novel biochars were prepared from corn cob to investigate the degradation mechanism of methyl orange (MO) dye through the method of photoexcitation. The corn cob biochars were characterized by SEM, XRD, FTIR, XPS, and EPR techniques and the properties of adsorption and degradation of methyl orange were investigated. The adsorption model of corn cob biochar for MO could be fitted to the pseudo-second-order kinetic equation and the Freundlich thermodynamic equation. The maximum adsorption capacity of corn cob biochar was 86.38 mg g(-1) for MO. The adsorption mechanism of MO was the result of synergistic effects of physical and chemical interactions such as electrostatic interactions, electron sharing, and electron exchange. The characterization results confirmed that the corncob biochar exhibits a graphene-like structure with abundant hydroxyl functional groups that can share and transfer electrons under the condition of photoexcitation. The degradation mechanism of MO by corn cob biochar under visible light was confirmed that photoelectrons can induce graphite-like structure and oxygen to generate highly active hydroxyl radicals to degrade MO during the adsorption-photodegradation process. The findings of this study will provide new insights into the application of biochar in the removal of azo dyes.