Co-catalyzed boudouard reaction-derived biochar for enhanced persulfate activation

Abstract

Carbon etching of biochar via the Boudouard reaction offers a promising thermochemical strategy for tailoring pore structure and surface functionalities. However, the practical application of CO2-assisted biochar modification is often constrained by the high activation energy and slow kinetics of the Boudouard reaction. In this study, cobalt (Co) was introduced as a catalytic promoter to accelerate the Boudouard reaction during CO2-assisted pyrolysis of wheat straw (WS). Thermogravimetric analysis revealed that Co impregnation decreased the onset temperature of the Boudouard reaction from 740 to 460 °C, indicating enhanced reaction kinetics. The resulting Co-loaded biochar synthesized under CO2 atmosphere CoWSB (CO2) exhibited a well-developed mesoporous structure, increased abundance of electron-rich Csingle bondO surface functionalities, and highly dispersed Co active sites. Catalytic performance evaluation demonstrated that CoWSB (CO2) achieved complete removal of bisphenol A through activation of peroxydisulfate and peroxymonosulfate, outperforming the counterpart biochar prepared under an inert N₂ atmosphere. In addition to improved catalytic activity, Co impregnation promoted syngas production during WS pyrolysis, yielding 138.9 mmol of CO and 10.7 mmol of H2. This enhancement is attributed to Co-catalyzed reforming and conversion of volatile oxygenated intermediates, which facilitates CO formation via the Boudouard reaction and secondary cracking reactions.