The object of this study was to evaluate the efficiency of safranin O dye removal with application of magnetite nanoparticles (Fe3O4 NPs) as adsorbent. For this propose. NPs of Fe3O4 were synthesized via a chemical precipitation method with addition of sodium hydroxide to solutions of Fe2+ and Fe3+. The prepared NPs were characterized by XRD and TEM and the applicability of the synthesized NPs for removing of safranin O as a cationic dye from aqueous solutions was investigated. The surface of Fe3O4 NPs was modified with addition of sodium dodecyl sulfate as an anionic surfactant. The effects of various parameters on the removal efficiency of safranin O such as the type and amount of surfactant, pH of solution, salt effect and contact time were studied and optimized. The studies of sorption kinetics of the dye showed a rapid sorption dynamics by a second-order kinetic model, suggesting chemisorption mechanism. Dye adsorption equilibrium data were fitted well to the Langmuir isotherm and the maximum monolayer capacity q(max) was calculated from the Langmuir as 769.23 mg g(-1). The obtained results indicate that sodium dodecyl sulfate modified Fe3O4 NPs can be used as an efficient adsorbent material for adsorption of cationic dyes from aqueous solutions. (C) 2010 Elsevier B.V. All rights reserved.