Fe3O4 nanoparticles modified with polyacrylic acid (PAA) were fabricated using a solvothermal approach. The adsorption behavior of Glycine, L-Arginine and L-Tyrosine on the PAA coated Fe3O4 nanoparticles was investigated, and the adsorption isotherm of these amino acids on magnetite nanoparticles at different pH values was described. The amount of amino acid adsorbed increases as the concentration of amino acid is increased. The adsorption capacities at different pH values are in the order of pH 5 > pH 3 > pH 11. Among the three amino acids, adsorption capability increases in the order of Glycine > L-Arginine > L-Tyrosine at pH 5. The desorption experiments and amounts of amino acids desorbed were analyzed to explore the adsorption mechanism. It is suggested that electrostatic interaction plays an important role in the adsorption behavior. (C) 2013 Elsevier B. V. All rights reserved.