Efficient degradation of trimethoprim with ball-milled nitrogen-doped biochar catalyst via persulfate activation

This study explored a novel eco-friendly metal-free biochar catalyst for trimethoprim (TMP) degradation in an aqueous solution. The preparation of a ball-milled and N-doped mulberry biochar (BMNMB) for the activation of persulfate to degrade an antibiotic. BMNMB exhibits a large contact surface area and high colloidal stability compared to pristine biochar, ball-milled, and thermally treated biochar (BMMB). Surface analysis studies confirmed the heteroatom doping of the ball-milled biochar materials. The degradation efficiency of TMP in the BMNMB900/PS (>97%) was higher than those of the BMMB900/PS (73%) and pristine MB/PS (24%) systems. The TMP removal treads were further verified by the pseudo-first-order kinetic model (PFOKM). The effective degradation of TMP was obtained under neutral pH conditions. The heterogeneous catalytic reaction performance was examined using the Langmuir–Hinshelwood (L–H) kinetic model. The anions had a negative impact on the catalytic activation of BMNMB900 with PS. The chemical scavenger analysis was confirmed via both radical (HO• and SO4•−) and non-radical (1O2) reactive oxygen species (ROS) formed in the BMNMB900/PS system. Further, substantial evidence of 1O2 formation in the BMNMB900/PS system was observed in the electron spin resonance (ESR) analysis in the presence of D2O. Moreover, the linear sweep voltammogram also clearly demonstrated the electron transfer process in the BMNMB900/PS system. The TMP degradation mechanisms were proposed via the intermediate analysis using ultra-high-performance liquid chromatography with mass spectroscopy (UHPLC-MS/MS). The BMNMB900 catalyst with PS system successfully demonstrated the reusability of a catalyst in TMP degradation.