Synergetic adsorption and Fenton-like oxidation for simultaneous removal of ofloxacin and enrofloxacin using green synthesized Fe NPs

Due to the widespread use of antibiotics worldwide in both medicine and agribusiness, many wastewaters often contain a range of different fluoroquinolone antibiotics such as ofloxacin (OFL) and enrofloxacin (ENR) in elevated concentrations. Simultaneous removal of such mixed antibiotics is a major challenge where the utility of using nanomaterials for such purposes is unknown. In this study, pre-adsorption followed by Fenton-like oxidation (sequential Fenton-like oxidation) was developed and shown to be useful for the simultaneous removal of OFL and ENR, with removal efficiencies of 91.8 and 90.7%, respectively. Changes in the surface of Fe NPs, before and after exposure to both FQs, were characterized by field emission scanning electron microscopy (FESEM), Transmission electron microscope (TEM), Fourier-transform infrared (FTIR), X-ray diffraction pattern (XRD) and X-ray photoelectron spectroscopy (XPS). This comparative characterization revealed that both OFL and ENR were initially adsorbed on to the surface of Fe NPs, and then Fe NPs were corroded to form Fe3O4 via sequential Fenton-like oxidation. Initial kinetic adsorption data best fit a pseudo-second-order kinetic model (R-2 >= 0.913), while the subsequent Fenton-like oxidation process best fit a pseudo first-order model (R-2 >= 0.964). Oxidation products detected by the high performance liquid chromatography mass spectrometry (HPLC-MS) confirmed that overall removal mechanism of both OFL and ENR involved oxidative degradation. Finally, the recycling and application in real wastewaters of sequential Fenton-like oxidation of the Fe/H2O2 system was evaluated.