High-efficiency degradation of p-cresol in water by ferrous sulfide activated peroxydisulfate and its mechanism

P-cresol ( p -C) is a highly toxic and refractory phenolic pollutant, which is frequently found in industrial wastewater. Since the deficiencies of traditional treatment processes, it is easily transferred to water environment, posing a potential threat to ecological safety and human health. Hence, high-efficiency degradation of p -C in water is an urgent but challenging task. In this study, a kind of low-cost commercial ferrous sulfide (FeS) was employed to activate peroxydisulfate (PDS) for the degradation of p -C in water, and the main impact factors, active species and reaction mechanism were investigated. The results revealed that p -C (20 mg/L) could be thoroughly degraded in 20 min in FeS-activated PDS system over a wide initial pH range of 3.0–9.0, and the mineralization ratio reached 68.8 %. Based on the results of radical scavenging experiment, electron paramagnetic resonance (EPR) trapping experiment and XPS analysis, the mechanism of p -C degradation was proposed. P-cresol degradation in FeS/PDS system mainly follows heterogeneously catalytic oxidation mechanism, in which surface ≡Fe 2+ active PDS to generate surface-bound radicals (SO 4s •– and HO s • ), while the free radicals (SO 4L •– and HO L • ) diffusing from the surface of FeS catalysts to the solution are primarily responsible for p -C degradation, and the HO L • is the dominant one. The sulfur species of S 2− and S n 2− on FeS surface provided electrons to facilitate a continuous ≡Fe 3+ /≡Fe 2+ circulation, promote PDS activation and thus enhance p -C degradation. Conclusively, the FeS/PDS system could have a great potential for the degradation of p -C and the like recalcitrant pollutants in water.