Superparamagnetic ascorbic acid-coated Fe3O4 nanoparticles with a high specific surface area were successfully synthesized via an environmentally friendly hydrothermal route in the absence of any templates. The as-synthesized ascorbic acid-coated Fe3O4 nanoparticles have a diameter of less than 10 nm, thus leading to a high specific surface area of about 179 m(2)/g, which is even larger than those of well-defined mesoporous structures. The only used capped agent is ascorbic acid, which serves as a functionalized molecule to make sure the high dispersibility and stability of the ascorbic acid-coated Fe3O4 nanoparticles in aqueous solution. The ascorbic acid-coated Fe3O4 nanoparticles exhibit superparamagnetic properties at room temperature and saturation magnetization approaches 40 emu g(-1). The ascorbic acid-coated Fe3O4 nanoparticles were evaluated as an absorbent to remove heavy metal arsenic from wastewater. The adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 16.56 mg/g for arsenic (V), and 46.06 mg/g for arsenic (III). (C) 2012 Elsevier B.V. All rights reserved.