Peroxide activation by microbially synthesized sulfidated iron: Comparison against abiotic iron-based materials in terms of treatment efficiency and oxidative degradation pathway

This study demonstrated the application of biogenic sulfidated iron (B-FeS), produced via anaerobic digestion of Desulfovibrio desulfuricans using sulfate as the terminal electron acceptor, for peroxide activation. B-FeS was assessed against chemically prepared zerovalent and sulfidated iron (ferrous sulfide and pyrite) with respect to their ability to activate peroxydisulfate (PDS) and H2O2. Regardless of the peroxide type, B-FeS outperformed benchmark iron activators in treating 4-chlorophenol due to its resistance to iron corrosion and the high content of reduced sulfur. The roles of oxidizing radicals were confirmed based on the effects of alcohol-based quenchers, multi-activity assessment, electron paramagnetic resonance spectral features, and product analysis. The pH-dependent efficiency of sulfoxide-to-sulfone conversion suggested that high-valent iron species acted as the secondary oxidant in all iron/peroxide systems, and the contribution was more pronounced when PDS and B-FeS were used. Microbial sulfidation as a catalyst regeneration strategy recovered the peroxide activation capacity of oxidized B-FeS. [Display omitted] •Biogenic iron sulfide outperformed abiotic heterogeneous iron in peroxide activation.•Slow iron dissolution increased the peroxide utilization efficiency of iron sulfides.•Superiority of biogenic iron sulfide was due to its high content of reduced sulfur.•The role of high-valent iron became more significant with iron sulfide and PDS.•Peroxide activation capacity of oxidized iron sulfide was microbially recovered.