Reactive Nitrogen Species Mediated Degradation of Estrogenic Disrupting Chemicals by Biochar/Monochloramine in Buffered Water and Synthetic Hydrolyzed Urine

There is increasing concern about the severe endocrine-related health problems because of the discharge of estrogenic disrupting chemicals (EDCs) into the natural environment. In this study, we investigated the activation of monochloramine (NH₂Cl) by biochar [pyrolyzed by cotton straw at 350 °C (Cot350), wheat straw at 350 and 700 °C (WS350 and WS700), and corn straw at 350 and 700 °C (CS350 and CS700)] for the degradation of estradiol (E2) and ethinylestradiol (EE2). Approximately 95% of parent E2 and EE2 was removed by Cot350/NH₂Cl in buffered solution, and 87% of E2 and 75% of EE2 were removed in urine within 24 h. Electronic paramagnetic resonance analysis and radical-quenching experiments showed that biochar activated NH₂Cl and primarily generated ^•NO radicals for the degradation of the EDCs. The nitrogen and silicon elements of Cot350 served as primary catalytic sites for NH₂Cl activation, whereas the sp²-hybridized carbon on WS700 and CS700 played a major role. The effect of major urine components (i.e., ammonia species, chloride, and bicarbonate) on the reaction pathways of biochar/NH₂Cl was also elucidated. This study provides new insights into the reaction pathways of NH₂Cl activation by biochar and suggests potential applications for other carbonaceous materials for NH₂Cl activation.