A CoFe2O4-Cr2O3-SiO2 fluorescent magnetic nanocomposite (FMNC) has been synthesized by a combined sonochemical co-precipitation method. Remarkable feature of the FMNC is its high band gap energy (3-4 eV). Photocatalytic activity of the FMNC has been examined for degradation of methylene blue in aqueous solution under UV irradiation (12 mW Hg lamp, major wavelength 400 nm). The catalyst could be separated from aqueous media by applying external magnetic field and hence could be reused without any significant loss of its activity. (C) 2011 Elsevier B.V. All rights reserved.