A new type of magnetic adsorbent was prepared using a simple one-step synthesis for the removal of Zn (II) and Cd(II) from aqueous solution. Structure characterization demonstrated that the surface of the magnetic nanoparticles (MNPs) had been modified by L-arginine. Factors that affect the adsorption of Zn(II) and Cd(II) onto the MNPs modified with L-arginine (MNPs-L), such as pH, ionic strength, initial concentration, contact time, temperature, and compete adsorption, were investigated. The adsorption kinetic data followed the pseudo-second-order model (PSOE) and the intra particle diffusion model (IPD). Isotherm data demonstrate that the Langmuir absorption model was the best-suited model for this research, and the calculated maximum adsorption capacities of Zn(II) and Cd(II) were 150.4 mg/g and 120.2 mg/g, respectively. Thermodynamic parameters indicated a spontaneous and endothermic adsorption process. In addition, regeneration studies suggested that MNPs-L were stable. Thus, MNPs-L could be a promising material for removing Zn(II) and Cd(II) from wastewater. (C) 2017 Elsevier B.V. All rights reserved.