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.