Reactive oxygen species formation in thiols solution mediated by pyrogenic carbon under aerobic conditions

Highlights: • Pollutants were oxidized by activated carbon/L-cysteine under aerobic conditions. • O₂^{• −}, ^• OH and H₂O₂ were the main species formed. • EPR and quenching studies were used to identify the reactive oxygen species. • Other carbons such as biochar and graphite could also mediate ^• OH formation. Previous studies have demonstrated that pyrogenic carbon can mediate the reductive degradation of pollutants in solutions containing reducing reagents under anaerobic conditions. However, few studies have investigated oxidative species formation and pollutants transformation directly mediated by pyrogenic carbon under aerobic conditions. In this study, we found that activated carbon (AC) can not only mediate reductive hexachloroethane degradation in the absence of O₂ but also mediate the oxidation of As(III) and sulfanilamide in L-Cysteine (Cys, a naturally abundant thiol compound) solution under aerobic conditions. Electron paramagnetic resonance and quenching studies indicated that O₂^{• −}, H₂O₂ and ^• OH was formed in Cys/AC system under aerobic conditions. High O₂ content favored the formation of ^• OH, indicating that O₂ participated in ^• OH production. In addition, an increase in AC concentration and specific surface area led to increased formation of ^• OH, and other pyrogenic carbon materials such as biochar and graphite were also found capable of mediating the formation of ^• OH. This study demonstrates that pyrogenic carbon could mediate ^• OH formation in solutions containing reductive reagents under aerobic conditions, which provides a new perspective for studying the behavior of pyrogenic carbon in the environment and its role in biogeochemical processes.