Fe3O4 spheres with loose structure assembled by nanospheres with diameters around 50 nm are synthesized via a facile one-pot solvothermal method. Series of Fe3O4 morphologies are obtained by controlling the concentration of cetyltrimethylammonium bromide (CTAB). The saturation magnetization of Fe3O4 nanospheres is about 87.3 emu/g. Adsorption ability and mechanism of all samples are investigated. Experiments demonstrate that adsorption capacity is closely related with the double impacts of electrostatic interactions and specific surface area. (C) 2011 Elsevier B.V. All rights reserved.