In this study, a zirconium nanoparticle sorbent for significantly enhanced adsorption of arsenate (As(V)) was successfully synthesized. The characterization of the zirconium nanoparticle sorbent and its adsorption behavior for arsenate were investigated. The HRTEM micrographs showed that the sorbent was nanoscale with particle sizes ranging from 60 to 90 nm. The thermal gravimetric and elemental analyses indicated that the sorbent had a molecular formula of Zr-2(OH)(6)SO4 center dot 3H(2)O. The X-ray diffraction study revealed that the sorbent was amorphous. The potentiometric titration study demonstrated the surface charge density of the sorbent decreased with an increase in solution pH, and the pH of zero point charge of the sorbent was around 2.85. The kinetics study showed that most of the uptake took place in the first 6 h, and the adsorption equilibrium was obtained within 12 h. The optimal pH for As(V) adsorption was between 2.5 and 3.5. The Langmuir equation well described the adsorption isotherm; the maximum adsorption capacity of 256.4 mg As/g was found at the optimal pH, better than most of sorbents available in the market. The presence of fluoride or nitrate did not obviously affect the adsorption of As(V) onto the sorbent; however, the existence of humic acid, phosphate or silicate in aqueous solution significantly reduced the uptake of As(V). The humic acid did not cause the reduction of the As(V). The FTIR and XPS spectroscopic analyses revealed that surface hydroxyl and sulfur-containing groups played important roles in the adsorption. (C) 2010 Elsevier Inc. All rights reserved.