Degradation of bensulfuron methyl by nitrogen/boron codoped biochar activated peroxydisulfate at lower temperature

Bensulfuron methyl (BSM) is the most widely used herbicide in rice paddy field. The removal and mechanism of BSM by advanced oxidation techniques were seldom studied, especially in the cold region. Herein, we prepared corn straw biochar (BC) and codoped it with N and B to degrade BSM by activating peroxydisulfate (PDS) at different temperatures (5, 15, 25, and 35 °C). At neutral and acidic pH, 92.7% of BSM was eliminated within 30 min at 15 °C. Graphitic N and BC3 were identified as dominant species towards PDS activation, providing more positively charged carbon atoms. Electron paramagnetic resonance, quenching experiment, and electrochemical impedance spectroscopy confirmed that 1O2 contributed more than radical pathways (SO4•-, •OH, and •O2−) in the degradation of BSM. Electron transfer was also responsible for BSM degradation. Density functional theory calculations showed N-B codoped BC enhanced the surface affinity of PDS, changed the electronic structure, increased the electron transfer rate, and improved the catalytic ability. BC-NB900 exhibited stable catalytic performance in the presence of various anions and reusability test, indicating its potential for practical application. This study develops an efficient and practical technique for removing residual BSM and provides a feasible approach for eliminating organic contaminants in different regions.