Synergistic chromium(VI) reduction and phenol oxidative degradation by FeS2/Fe0 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 FeS2 sulfidated zero valent iron (FeS2/Fe0) 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 FeS2/Fe0+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 Fe2+ 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 SO42−, whose production speed was accelerated by the PS activation to oxidize phenol and FeS2, was conductive to corrode Fe0 to regenerate the surface-bound Fe2+ for reducing Cr(VI) and oxidizing phenol. It is potential to develop a high-performance and large-scaled FeS2/Fe0-based redox platform to remediate the complex pollution of Cr(VI) and organics.