Magnetic nanoparticles are exceptional adsorbent materials due to their unique magnetic properties and good adsorption capacity. In this study, a new method combining nanoparticle adsorption and magnetic separation was investigated for the removal of cadmium ions from the drilling fluid and its efficiency was studied. Magnetic iron oxide nanoparticles were successfully synthesized, characterized and evaluated by X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Infrared spectroscopy (IR). The effects of various factors, e.g. pH, shaking rate, retention time and magnetic adsorbent doses on the adsorption process were also studied. The concentrations of cadmium ions were measured with both Atomic Absorption Spectroscopy (AAS) and Electrochemical Method. Adsorption reached equilibrium within 10 min. The maximum adsorption occurred at pH of 6 and shaking rate of 50 rad/s (480 RPM) with 3.2 mg of adsorbent for an initial Cd concentration of 5 mg/L. The adsorption data were analyzed and fitted well by Freundlich isotherm. (C) 2013 Elsevier Ltd. All rights reserved.