Magnetite nanoparticles were applied to remove Cu (II) from aqueous solutions. The highly crystalline nature of the magnetite structure with a diameter of around 10 nm was characterized with transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The surface area was determined to be 115.3 m(2)/g. Surface chemical properties of magnetite at 25 degrees C in aqueous suspensions were investigated. Batch experiments were carried out to determine the adsorption kinetics and mechanism of Cu (II) by these magnetite nanoparticles. The Cu (II) uptake was mainly governed by surface complexation adsorption. The adsorption process was found to be pH-dependent. The Cu (II) adsorption onto magnetite from NaCl and NaClO4 solutions (0.001 to 0.1 mol/L) revealed that Cu (II) adsorption behavior was a function of the concentration and type of supporting electrolyte. The adsorption process followed the pseudo-second order equation (r(2)=0.9876) and Fractional power equation (r(2)=0.9882) very well. The adsorption data fitted well with the Freundlich (r(2)=0.9938) and Langmuir isotherm (r(2)=0.9944) equations and the isothermal constants were calculated. Preliminary results indicate that magnetite nanoparticles may be used as an adsorbent for the removal of Cu (II) from wastewater. (C) 2011 Elsevier B.V. All rights reserved.