Degradation mechanism of Bisphenol S via hydrogen peroxide/persulfate activated by sulfidated nanoscale zero valent...

Fenton-like oxidation processes are widely used to degrade recalcitrant organic pollutants, but are limited by narrow application pH and low reaction efficiency. This study investigated the synchronous activation of H₂O₂ and persulfate (PDS) by sulfidated zero valent iron (S-nZVI) in ambient conditions for Fenton-like oxidation of bisphenol S (BPS), an estrogenic endocrine-disrupting chemical. The activation of S-nZVI induced H₂O₂ or PDS could be greatly enhanced with the assistance of PDS and H₂O₂, respectively, even across a wide range of pH value (3-11). The first-order rate constant of S-nZVI/H₂O₂/PDS, S-nZVI/PDS and S-nZVI/H₂O₂ systems was found to be 0.2766 min^-1, 0.0436 min^-1, and 0.0113 min^-1, respectively. A significant synergy between H₂O₂ and PDS was achieved when the PDS-H₂O₂ molar ratio was above 1:1, and where sulfidation promoted iron corrosion and decreased solution pH were observed in the S-nZVI/H₂O₂/PDS system. Radical scavenging experiments and electron paramagnetic resonance (EPR) investigations suggest that both SO₄^•- and ^•OH were generated and that ^•OH played a crucial role in BPS removal. Furthermore, four BPS degradation intermediates were detected and three degradation pathways were proposed in line with the HPLC-Q-TOF-MS analysis. This study demonstrated that compared to the traditional Fenton-like system, the S-nZVI/H₂O₂/PDS system could be a more efficient, advanced oxidation technology capable of being used across a broad pH range for emerging pollutants' degradation.