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

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.