Oxidative removal of antibiotic resistant E. coli by sulfidated zero-valent iron: Homogeneous vs heterogeneous activation

Abstract

As an emerging contaminant in water, antibiotic resistant bacteria are threatening the public health gravely. In this study, sulfidated ZVI was used to activate persulfate, for antibiotic resistant E. coli and antibiotic resistant genes removal. Impressively, 7 log of antibiotic resistant E. coli was inactivated within 30 min, in sulfidated ZVI activated persulfate system (S/Fe = 0.05). Electron paramagnetic resonance and free radical quenching experiments suggested that sulfidation treatment did not change the specie of radicals. SO4•−and HO• were the main reactive oxygen species for the removal of antibiotic resistant E. coli and genes. Investigation on the activation mechanism of persulfate indicated that persulfate decomposition was mainly attributed to heterogeneous activation. More importantly, in-situ characterization (ATR-FTIR) indicated that the main charge transfer complex was formed on the surface of sulfidated ZVI, which would predominantly mediate the generation of SO4•− and HO•. Finally, the proposed system was evaluated in modeling water and secondary effluent. Results revealed that only 2.86 log and 0.84 log of antibiotic resistant E. coli were inactivated in the presence of NOM (10 mg/L) and HCO3– (84 mg/L), respectively. Besides, sulfidated ZVI activated persulfate system could be pH-dependent in actual wastewater treatment.