Rapid PFOS mineralization with peroxydisulfate activation process mediated by N modified Fe-based catalyst.

As the cheap and efficient catalysts, the iron-based catalysts have been considered as one of the most promising catalysts for peroxydisulfate (PDS) activation and the development of high-performance iron-based catalysts are attracting growing attentions. In this work, a magnetic Fe-based catalysts (Fe/NC-1000) was obtained by using Fe modified ZIF-8 as the precursor and used to activate the PDS for the degradation of perfluorooctane sulphonate (PFOS). Morphology and structure analysis showed that the resulted Fe/NC-1000 catalyst was displayed porous spheres (40-60 nm) and mainly composed of Fe0, FeNx and carbon. When Fe/NC-1000 was employed to activate the PDS (0.1 g/L of catalyst dosage, 0.5 g/L of PDS dosage and at initial pH of 4.6), the Fe/NC-1000/PDS system exhibited excellent efficiency (97.9 ± 0.1) % for PFOS (10 mg/L) degradation within 30 min. The quenching tests and EPR results revealed that the Fe/NC-1000/PDS system degraded PFOS primarily through singlet oxygen (1O2) evolution and electron-transfer process. Besides, based on the degradation byproducts determined by LC-MS-MS, the PFOS first occurred de-sulfonation to form PFOA, and then the resulted PFOA underwent stepwise defluorination in the Fe/NC-1000/PDS system. Density Functional Theory (DFT) calculations and electrochemistry tests strongly confirmed that Fe/NC-1000 exhibited high electron transfer efficiency, resulting in promoted performance on activating PDS. Importantly, the results of Ecological Structure-Activity Relationship (ECOSAR) analysis showed that the intermediates were lowly toxic during the PFOS degradation, manifesting a green process for PFOS removal. This study would provide more understandings for the persulfate activation process mediated by Fe-based catalysts for Perfluorinated alkyl substances (PFAS) elimination.