Amine-functionalized mesoporous Fe3O4 nanoparticles (AF-Fe3O4) were developed for the highly efficient removal of toxic heavy metal ions from water. AF-Fe3O4 were prepared by a new cost-effective and environmentally friendly procedure. The maximum amino-group grafted onto AF-Fe3O4 is 0.1790 mu g/mg by ninhydrin test. AF-Fe3O4 can be simply recovered from water with magnetic separations at low magnetic field within 1 min. Each adsorption of 50 mL 5 mg/L of Pb(II), Cd(II), and Cu(II) onto 10 mg of AF-Fe3O4 reached equilibrium within 120 min at pH 7.0. It agreed well to the Langmuir adsorption model with maximum adsorption capacities for Pb(II), Cd(II), and Cu(II) from 369.0 to 523.6 mg/g, which is larger than some other reports. The adsorption rates of Pb(II), Cd(II), and Cu(II) on AF-Fe3O4 fit pseudo-second order kinetic models (R-2 > 0.99). Thermodynamic studies illustrated the adsorption process was endothermic and spontaneous. AF-Fe3O4 was able to remove over 98% of Cu(II). Cd(II) and Pb(11) in 50 mL of solution containing 5 mg/L metal ions at optimized conditions. (C) 2012 Elsevier B.V. All rights reserved.