Synergistic Activation of Peroxydisulfate by Capping Biomolecules on Green Synthesized Iron Nanoparticles for Oxidation of Mixed E2 and Ee2

A low concentration of endocrine disrupting compounds (EDCs) has become a new environmental problem. In this work, green synthesized Fe nanoparticles (Fe NPs) were evaluated for their activation of peroxydisulfate (PDS) to degrade 17β-estradiol (E2) and 17α-ethinylestradiol (EE2). It is, however, unclear what the function of capping biomolecules on Fe NPs is. It was found that the oxygen-containing functional groups derived from capping agents on the surface of Fe NPs could synergistically activate PDS to generate sulfate radical (SO4•-) and hydroxyl radicals (•OH) by electron paramagnetic resonance spectroscopy (EPR). As a result, 98.3% of E2 and EE2 were removed by Fe NPs and PDS within 20 minutes. Furthermore, PDS could be activated for removing E2 and EE2 by Fe NPs in the wide initial pH 3.0 - 9.0. SEM-EDS and XPS spectra of Fe NPs before and after degradation confirmed that Fe(II) was a key factor in the activation of PDS. In addition, FTIR spectroscopy showed that the oxygen-containing functional groups were existed on surface of Fe NPs, which could synergistically activate PDS based on degraded products of E2 and EE2 analyzed by LC-MS. Finally, synergistic activation of PDS by capping biomolecules on Fe NPs were proposed