Decolorization of Acid Orange II dye by peroxymonosulfate activated with magnetic Fe3O4@C/Co nanocomposites

Abstract

New metallic cobalt loaded magnetic nanocomposites (Fe₃O₄@C/Co) were prepared by calcination and in situ reduction of the Co²⁺-impregnated magnetic carbon nanoparticles of Fe₃O₄@C at 900 °C under a nitrogen atmosphere. Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), vibrating sample magnetometry, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the properties of the composites and the loading of metallic Co⁰ in the material was clarified. The catalytic properties of the nanocomposites Fe₃O₄@C/Co in activating peroxymonosulfate (PMS) for decolorization of Acid Orange II (AO II) dye in aqueous solution were investigated. Fe₃O₄@C/Co nanocomposites exhibited high activity in PMS activation for AO II decolorization. Complete decolorization of AO II solution could be achieved in 20 min within near neutral pH range (pH 6.4–8.5), while a complete decolorization occurred in 40 min for the as-prepared solution without pH adjustment (pH 4.05). The effects of several parameters including pH, catalyst load, PMS concentration and reaction temperature on the catalytic activity were also investigated. Sulfate free radicals activated from PMS were proposed to be the dominant active species in the “Fe₃O₄@C/Co + PMS” system for AO II decolorization. The catalytic and decolorization mechanism was suggested. The catalyst Fe₃O₄@C/Co could be recycled easily by a magnet with good reusability. This study provides a promising method for the activation of “green” oxidant, PMS, by the new magnetic nanocomposites for environmental remediation and oxidation catalysis.