Mesoporous gamma-Fe2O3/SiO2 nanocomposite containing 30 mol% of gamma-Fe2O3 was prepared by a template-free sol-gel method, and its removal ability for methyl orange (MO) was investigated. The nanocomposite was characterized using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), Fourier transform infrared (FTIR) absorption measurements, nitrogen adsorption-desorption measurements, and magnetic measurements. The synthesized gamma-Fe2O3/SiO2 nanocomposite has a mesoporous structure with an average pore size of 3.5 nm and a specific surface area of 245 m(2)/g, and it exhibits ferrimagnetic characteristics with the maximum saturation magnetization of 20.9 emu/g. The adsorption of MO on the nanocomposite reaches the maximum adsorbed percentage of ca. 80% within a few minutes, showing that most of MO can be removed in a short time. The MO adsorption data fit well with both Langmuir and Freundlich adsorption isotherms. The maximum adsorption capacity of MO is estimated to be 476 mg/g. (C) 2010 Elsevier B. V. All rights reserved.