Fe3N sites anchored reduced graphene oxide activate peroxymonosulfate via singlet oxygen dominated process: Performance and mechanisms

Advanced oxidation processes (AOPs) have attracted much attention due to their adaptability to complex water environments. In this study, new catalysts (Fe/N-rGOs) with three dimensional (3D) interpenetrating structure were fabricated from the iron phthalocyanine (FePc) anchoring on reduced graphene oxide (rGO) for tetracycline (TC) degradation by activating peroxymonosulfate (PMS). Among them, the Fe/N-rGO-4 catalysts with high Fe-Nx center density exhibited the best degradation efficiency and the highest value of pseudo-first-order degradation reaction kinetic (k = 0.185 min−1), which was approximately 18.5, 4.2, and 2.9 times higher than the rates achieved by the pristine PMS, rGO/PMS, and calcining FePc nanoclusters without rGO (Fe/N NPs/PMS) systems, respectively. Besides, Fe/N-rGO-4 exhibited satisfactory catalytic activity over a wide pH range (3.0–9.5) and remarkable stability of degradation performance after four consecutive cycles. Quenching experiments and electrochemical analysis demonstrated that 1O2 was the primary reactive species, which was facilitated by the mediated electron transfer originating from the C-N group with graphitic N at the defective edges of rGO. The π-conjugated region resulting from π-π stacking interaction between rGO and FePc is the pathway of electron transfer. Furthermore, Fe3N sites were proved as the primary catalytic active sites, which dominated the catalytic performance. Three degradation pathways of TC including twelve intermediates were proposed based on the Liquid Chromatograph Mass Spectrometer (LC-MS) analysis. Generally, this work highlighted the great potential of Fe/N-rGOs catalysts and provided a new insight into the synthesis of high-performance carbon-based catalysts for environmental remediation.