The widespread occurrence of antibiotics in water environment, especially the recalcitrant sulfamethoxazole (SMZ), has sparked increasing concern due to their potential to threat non-target organisms, contaminate food and induce bacterial resistance. In this study, magnetic graphitized biochar (GMBC) was synthesized via a facile one-step strategy employing pine wood-derived biochar as precursor and with potassium ferrate (K2FeO4) modification, and introduced as heterogeneous catalyst for persulfate (PS) activation and SMZ degradation. Utilizing K2FeO4 as both activator (KOH) and catalyst (Fe), porous structure, high graphitization degree, abundant electron-rich functional groups and iron loading of GMBC were simultaneously achieved, which afforded the high catalytic efficiency (almost 100 % degradation of SMZ within 60 min) through accelerating electron transfer. Pyrolysis temperatures affected the structure and catalytic performance of GMBCs. A systematic mechanistic study, including quenching experiment, electron spin resonance analysis and electrochemical measurements, unveiled that both radical pathways (HO center dot, SO4 center dot- and O-2(center dot-)-mediated oxidation) and non-radical pathways (electron shuttle and O-1(2)-mediated oxidation) were responsible for the SMZ degradation. Vacancies/defective edges formed on graphitized carbon framework, iron loading sites and the electron-rich ketonic group might be the active sites. In this process, GMBC played versatile roles in accumulating reactants, activating PS as well as mediating the electron transfer from SMZ to PS. Benefited from the multiple mechanisms, the GMBC/PS system can maintain superior oxidation efficiency under various environment conditions, with high anti-interference ability to surrounding compounds and solution pH. This study proposes an economic and green template-free strategy to prepare graphitized biochar catalyst for PS activation and gives underlying insight into the multiple roles of biochar in the eco-friendly remediation of contaminated water. (C) 2020 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.