Activation of peroxymonocarbonate by magnetic bimetal in porous carbon spheres for effective norfloxacin degradation

Abstract

Magnetic bimetal encapsulated in porous carbon spheres (Co/Cu@CS) was synthesized using chitosan by a gelation pyrolysis approach and its catalytic activities for peroxymonocarbonate (PMC) activation were assessed through norfloxacin (NOR) degradation in this work. The as-prepared composite exhibited an irregular spherical structure with an average diameter of 880 µm, and Cu and Co were uniformly distributed in the microspheres according to scanning electron microscope images. Zero-valence cobalt and copper were the dominant species according to the X-ray diffraction and photoelectron spectra. The transformation of graphitic and dangling carbon from chitosan was proven by the Raman and infrared spectra. The surface area and saturation magnetization of Co/Cu@CS were calculated as 133.7 m2/g and 39.2 emu/g, respectively. Co/Cu@CS exhibited excellent catalytic activities for unsymmetrical peroxides during almost complete NOR removal and showed good stability and the lowest metal leakage in the activated PMC degradation system because of the buffer function of bicarbonate. The degradation profiles of antibiotics in the Co/Cu@CS activated PMC system followed the typical pseudo-first-order kinetic model and the activation energy of NOR degradation was derived to be 17.0 kJ/mol. Singlet oxygen and hydroxyl radical were dominant active species and carbonate radical also played a significant role during NOR removal according to the scavenging experiments and electron spin resonance spectra. Three NOR degradation pathways were proposed based on 13 intermediate identification and the NOR pharmacophores, such as quinolone or piperazinyl moieties, were verified to be destroyed. The Co/Cu@CS activated PMC system might provide a potential choice for antibiotic pollution remediation.