Synergistic chromium(VI) reduction and phenol oxidative degradation by FeS/Fe and persulfate.

It is a challenge to simultaneously treat the combined pollutants of chromium(VI) (Cr(VI)) and organics (such as phenol) in wastewater. Here, a stable and efficient redox system based on FeS sulfidated zero valent iron (FeS/Fe) and persulfate (PS) was developed to synchronously remove Cr(VI) and phenol. 100% of phenol (10 mg/L) was oxidized in 10 min and Cr(VI) (20 mg/L) was completely reduced to Cr(III) in 90 min in the FeS/Fe+PS system with a pH range of 3.0-9.0, respectively. phenol was selectively oxidized without re-oxidizing Cr(III) in such system. The surface-bound Fe was the major reactive species to synchronously reduce Cr(VI) and oxidize phenol. The mechanisms were elucidated that the phenol degradation was accelerated by the generated Cr(III) complexing with its products, and that SO, whose production speed was accelerated by the PS activation to oxidize phenol and FeS, was conductive to corrode Fe to regenerate the surface-bound Fe for reducing Cr(VI) and oxidizing phenol. It is potential to develop a high-performance and large-scaled FeS/Fe-based redox platform to remediate the complex pollution of Cr(VI) and organics.