Fe3O4 magnetic nanoparticles (MNPs) were synthesized by a co-precipitation method. The phase purity was confirmed by X-ray powder diffraction (XRD) analysis. The crystal size was found to be 10 nm from transmission electron microscopy (TEM). It is evidenced that the surface of FC3O4 MNPs was modified by sodium citrate. The Fe3O4/ZnO core/shell MNPs were obtained by coating the MNPs with direct, precipitation using zinc acetate and ammonium carbonate. The precursor was firstly dried and then calcined at 350 degrees C. The antioxidation tests indicated that the core/shell MNPs give better antioxidation than that of the Fe3O4 MNPs. The photocatalytic degradation of methyl orange revealed that the core/shell MNPs have higher photocatalytic activity than that of the ZnO nanoparticles. Separation of the core/shell MNPs from the aqueous suspension using a magnet provides an easy way to recycle the core/shell MNPs. After four-time recycling, the photocatalytic degradation percentage of the core/shell MNPs is about 70%. (C) 2007 Elsevier Ltd. All rights reserved.