Trace amount of Fe-induced defect structures of biochar to activate persulfate for ofloxacin degradation

s Biochar exhibited excellent performance in activating persulfate (PS) for the degradation of organic contaminants. However, the role of endogenous metals in the activation of PS needs to be clarified, which will hinder the understanding of the PS activation mechanism by biochar and the design of efficient biochar for PS activation. In this study, biochars were prepared at different temperatures using cellulose, and trace amounts of Fe (0.069 %) and Mn (0.056 %) were incorporated separately or together into biochar to mimic the endogenous metals whose concentrations were consistent with the ones in local corn stalks. Our results demonstrated that a trace amount of Fe could greatly enhance the removal of ofloxacin (OFL) in the C1000-Fe system. Removing metals from biochar via acid-washing did not significantly impact the removal efficiency of OFL. The Raman analysis showed that Fe could increase the defect structures in C1000-Fe, which were converted during the cycling experiments, indicating they participated in the activation of PS. ROS capturing and quenching experiments confirmed that the increased defect structures via Fe in C1000-Fe facilitate the activation of PS to generate superoxide anions (O 2 •− ) and then convert them into singlet oxygen ( 1 O 2 ) for OFL degradation. Our results highlighted that a trace amount of Fe in biochar enhanced its activation of PS for degradation of OFL via altering the carbon structure, not itself as the activation site, which will benefit understanding the role of endogenous metals in the activation of PS.