Magnetic iron nanoparticles calcined from biosynthesis for fluoroquinolone antibiotic removal from wastewater

Abstract Efficient methods for the removal of fluoroquinolone antibiotics from both surface and wastewaters are urgently required due to the significant global ecosystem disturbances elevated concentrations of such substances are causing. In this study, calcined magnetic iron nanoparticles (nFe) fabricated via a biosynthetic route were successfully used to remove two representative fluoroquinolone antibiotics, ofloxacin and pefloxacin from aqueous solution. The prepared nanoparticles were spherical with a particle diameter between 20 and 50 nm and were highly magnetic with a saturation magnetization of 58.5 emu g−1. Energy dispersion spectrum (EDS), Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectra (XPS) characterization all indicated the existence of substantial organic capping agent on the nanoparticles surface, which facilitated fluoroquinolone adsorption. The adsorption efficiency of ofloxacin and pefloxacin reached 100% within 300 min for a FQ concentration of 5 mg L−1. The adsorption of both ofloxacin and pefloxacin followed pseudo-second-order kinetics model and best fit the Freundlich adsorption isotherm model, with adsorption capacities of 12.8 and 16.2 mg g−1, respectively. Thermodynamic studies showed that for both fluoroquinolone adsorption was endothermic and spontaneous. A probable removal mechanism of ofloxacin and pefloxacin by nFe was proposed, involving pore-filling, hydrogen bonding, and electrostatic interaction. Regeneration and application studies, exposing nFe to real water samples, practically demonstrated that nFe was a high-quality adsorption material with significant potential for environmental remediation applications.