LAUSR

The goal of this work was to elucidate the ability of biochar materials prepared by different methods to degrade antibiotics by activating peroxymonosulfate (PMS). S atom was doped into biochar using diphenyl disulfide (DD), sodium thiosulfate (ST), and thiourea (TU) as S precursors. The different doped materials were used to activate PMS and tested for the ability to degrade tetracycline hydrochloride, sulfadiazine sodium salt, and levofloxacin hydrochloride. The average degradation efficiencies of DD-doped hydrothermal + pyrocarbon (DD-HPBC), TU-doped hydrothermal + pyrocarbon (TU-HPBC), and ST-doped hydrothermal + pyrocarbon (ST-HPBC) were 83.76%, 86.74%, and 93.60%, respectively, all higher than the degradation efficiency of the undoped material. When sodium thiosulfate-doped pyrocarbon (ST-PBC), hydrochar (ST-HBC), and hydrothermal + pyrocarbon (ST-HPBC) were used to activate PMS, the highest degradation efficiencies were achieved, with average rates of 71.59%, 78.22% and 97.20%, respectively. ST-HPBC exhibited the highest concentration of environmentally persistent free radicals (EPFRs), 9.47 × 1018 spin/g, among all biochar materials. Given this high concentration of EPFRs, use of ST-HPBC to activate PMS resulted in a very high rate of antibiotic degradation, and the concentration of EPFRs was positively correlated with the degradation efficiency. Increase of specific surface area, the thiophene S (-C-S-C-) ratio, and concentration of EPFRs in S-doped biochars promoted the degradation of antibiotics. For PMS activated by biochar, reactive oxygen species (ROS) degraded antibiotics in the order of sulfate radical (SO4•-) > singlet oxygen (1O2) > hydroxyl radical (•OH) > superoxide radical (•O2-). This work provides new insight into the application of S-doped sludge biochar materials.