Engineered magnetic cobalt/hydroxyapatite core-shell nanostructure: Toward high peroxymonosulfate activation via radical and non-radical mechanisms

Abstract

Sulfate radicals based advanced oxidation process has become an important research area for degradation of organic contaminants in water. Herein, a magnetic cobalt/hydroxyapatite namely Fe3O4 @Co/HAp with core-shell morphology and high operating stability was successfully synthetized. The Fe3O4 nanospheres were prepared through solvothermal reaction and then coated with Co/Hap by coprecipitation and ion exchange methods. The intrinsic crystallography of the as-prepared materials was characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). The surface of magnetic materials was studied by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The magnetic properties were measured at room temperature. The Fe3O4 @Co/HAp nanocomposite exhibited excellent catalytic activity for generation of active radicals from peroxymonosulfate (PMS) to degrade sulfanilamide (SA) as representative antibiotics. Besides, Fe3O4 @Co/HAp nanocomposite was able to degrade 94 % of SA after 5 min of reaction and removed 74 % of the total organic carbon (TOC) after 60 min. Furthermore, based on radical quenching experiments and electron paramagnetic resonance (EPR), HO•, SO4•− and 1O2 were contributed as the reactive species for SA degradation in the Fe3O4 @Co/HAp-PMS system. Eventually, based on the quenching experiment and EPR spectra, the plausible mechanism of generation of active radicals was proposed and schematized. The recycling experiment showed the excellent stability and reusability of the Fe3O4@Co/HAp-PMS system with facile magnetic separation. The eco-friendly using HAP as coating material for iron oxide as well as high catalytic activity over multiple catalytic cycles with negligible Co(II) leaching makes Fe3O4 @Co/HAp-PMS system a promising eco-friendly catalyst for sustainable water treatment and provides numerous novel opportunities for chemical catalysis.