Activation of persulfate by graphitized biochar for sulfamethoxazole removal: The roles of graphitic carbon structure and carbonyl group

Recently, the application of cheap, easily available biochar (BC) in advanced oxidation processes (AOPs) has received widespread attention. However, it is still a challenge to seek effective modification methods to prepare BC with high catalytic performance. In this study, a novel and environmentally friendly graphitized BC (WGBC) derived from wood chip was prepared, which exhibited excellent performance towards persulfate (PS) activation for sulfamethoxazole (SMX) removal as compared to original BC. Series characterizations confirmed that such improved catalytic performance was attributed to the well-established graphitic carbon structure and surface functionalized CO group. Free radical quenching and electron paramagnetic resonance (EPR) experiments qualitatively demonstrated that SO4·−, ·OH, 1O2 and O2·− were involved in the degradation of SMX, of which 1O2 and O2·− played the dominant roles. Moreover, a non-radical process in the WGBC/PS system was also proposed, in which WGBC worked as an electron transfer bridge for allowing electrons to transfer from SMX to PS to participate in SMX degradation. The WGBC/PS system exhibited a high anti-interference ability to Cl−, H2PO4−, NO3−, and humic acid (HA)-containing environments. This study provides a new idea for designing and constructing environmentally friendly and efficient biochar towards organic pollutants removal.