Insight into Flower-Like Greigite-Based Peroxydisulfate Activation for Effective Bisphenol a Abatement: Performance and Electron Transfer Mechanism

Abstract

This research offers insight into the activation of peroxydisulfate (PDS) by flower-like greigite (Fe3S4) (FLG) for bisphenol A (BPA) degradation in water. The as-prepared greigite was exclusively effective as a PDS activator in producing free radicals. FLG/PDS performed much better than Fe3O4/PDS and ZVI/PDS systems or some other earlier systems for BPA degradation. Only 0.02 g/L of FLG could remove more than 95% of BPA in 120 min. Cl− had little adverse impact on the BPA abatement, and 20 mg/L of NaHCO3 could decrease the BPA degradation rate to only 40%. FLG could be easily recycled by magnetic force, and it was reusable. Electron paramagnetic resonance and free radical scavenging tests demonstrated that sulfate radicals play a main role in the BPA degradation process. GC–MS and UHPLC-Q-TOF-MS were applied to detect the intermediates and the possible BPA degradation mechanism; three main pathways were proposed. The structure of nanosheets could effectively enhance the interaction between greigite and PDS and furthermore effectively produce radicals for BPA degradation. X-ray photoelectron experiments showed that the rate of Fe2+ decreased from approximately 37.0% to 19.5% and that typical peaks of S2− disappeared after PDS activation. This discovery indicated that S2− lost electrons to accelerate Fe2+/Fe3+ recycling when the Fe2+ species was changed to Fe3+. This research offered good insights into the Fe2+/Fe3+ species with sulfur elements effectively activating PDS for BPA degradation. Our study deepened the understanding of the electron transfer mechanism of sulfur-iron-based heterogeneous catalysis in environmental remediation.