Chitosan-coated magnetic nanoparticles (CCMNPs), modified with a biodegradable and eco-friendly biologic reagent, alpha-ketoglutaric acid (alpha-KA). was used as a magnetic nanoadsorbent to remove toxic Cu2+ ions from aqueous solution. The prepared magnetic nanoadsorbents were characterized by FTIR, TEM, VSM, XRD, and EDS. Factors influencing the adsorption of Cu2+, e.g., initial metal concentration, initial pH, contact time and adsorbent concentration were investigated. TEM images show that the dimension of multidispersed circular particles is about 30 run and no marked aggregation occurs. VSM patterns indicate superparamagnetic properties of magnetic nanoadsorbents. EDS pictures confirm the presence of the Cu2+ on the surface of magnetic nanoadsorbents. Equilibrium studies show that Cu2+ adsorption data follow Langmuir model. The maximum adsorption capacity (q(max)) for Cu2+ ions was estimated to be 96.15 mg/g, which was higher than that of pure CCMNPs. The desorption data show no significant desorption hysteresis occurred. In addition, the high stability and recovery capacity of the chitosan-coated magnetic nanoparticles modified with alpha-ketoglutaric acid (alpha-KA-CCMNPs) suggest that these novel magnetic nanoadsorbents have potential applications for removing Cu2+ from wastewater. (C) 2008 Elsevier Inc. All rights reserved.