Effect of phosphates on oxidative species generation and sulfamethoxazole degradation in a pig manure derived biochar activated peroxymonosulfate system

The peroxymonosulfate (PMS) oxidation processes have received considerable attention for water treatment. The influence of monohydrogen phosphate and dihydrogen phosphate on PMS system is still controversial. A biochar activated PMS system was constructed to investigate the HPO 4 2− /H 2 PO 4 − effects on sulfamethoxazole degradation. Results showed that the presence of H 2 PO 4 − inhibited PMS activation, while the co-existing HPO 4 2− played a positive role. Therefore, it might be inaccurate to assess the activation capacity of a catalyst for PMS activation when using phosphate as a buffer solution. Importantly, H 2 PO 4 − inhibited the function of C O, pyridine N and defects for PMS activation. However, HPO 4 2− promoted C O and graphitic N sites for sulfamethoxazole (SMX) degradation. The contributions of OH and SO 4 − to SMX degradation decreased with the increase of H 2 PO 4 − concentration. The production of SO 4 − was accelerated with the increase of HPO 4 2− concentration, promoting pollutants degradation. The contribution of 1 O 2 first increased and then decreased with the rise of HPO 4 2− /H 2 PO 4 − concentration. This study elucidated the roles of H 2 PO 4 − and HPO 4 2− in PMS system and revealed the corresponding specific influence mechanisms, promoting the application of PMS systems for antibiotic wastewater purification.