In this study, core-shell Fe-Fe2O3 nanostructures (FNs) were used to effectively activate sodium persulfate (Na2S2O8) to induce sulfate radicals (SO4-center dot) oxidation of methyl orange (MO) in aqueous solution (FNs/Na2S2O8). In this FNs/Na2S2O8 system, an enhanced degradation of MO was achieved in comparison with the Fe2+/Na2S2O8 system using ferrous ions as persulfate activator under neutral pH condition. An acid pH and a high persulfate to FNs molar ratio (Na2S2O8:FNs) were favorable to the MO oxidation in the FNs/Na2S2O8 process. We characterized the prepared FNs and the used FNs during the FNs/Na2S2O8 process via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) systematically. On the basis of the degradation and characterization results, we proposed a mechanism for the degradation of MO in the FNs/Na2S2O8 process, which involved in situ homogenous and heterogeneous activation of persulfate simultaneously. (C) 2013 Elsevier B.V. All rights reserved.