Biochar loaded with Cu(I) to activate peroxyacetic acid for sulfamethoxazole removal: Effect of electron transfer and free radicals

Cu/BC-PAA (Peroxyacetic acid) system was established in this study to remove sulfamethoxazole (SMX) from waters. Cu/BC-PAA achieved high elimination efficiency (91.2 %, k = 0.081 min −1 ) for SMX within 30 min. Cu (II) loaded on corn straw biochar was converted into form Cu (I) site. Characterization, electron paramagnetic resonance (EPR), and electrochemical analysis proved that Cu (I) and C O took part in the reaction, which accelerated electron transfer and produced free radicals and non-radicals (R-O· and singlet oxygen ( 1 O 2 )). Fukui index and Liquid Chromatograph Mass Spectrometer (LC–MS) analysis revealed that sulphonamide bond cleavage and isoxazole ring opening were the main detoxification pathway. Density functional theory (DFT) calculation exhibited the adsorption energy of Cu/BC (E ads  = −3.68 eV) enhanced the electron transfer between Cu (I) and PAA. The evaluation of anion effects, diverse water matrices, various sulfonamide antibiotics, and catalyst cycling tests demonstrated the Cu/BC-PAA system's exceptional stability, broad-spectrum applicability, and excellent reusability. This work successfully synthesized a stable environment-friendly catalyst for efficient activating PAA to eliminate antibiotics in waters.