delta-FeOOH nanoparticles were prepared by a fast, simple and cheap synthesis method for use as an adsorbent for As(V) in water. Rietveld refinement on XRD pattern confirmed that delta-FeOOH was successful synthesized. TEM images evidenced that the average particle sizes for delta-FeOOH is 20 nm, which provided a high surface area of 135 m(2) g(-1) and average pore sizes of 18 nm, as verified with BET measurements. Zeta potential revealed that the point of zero charge of delta-FeOOH is 8.4, which favored the As(V) adsorption on the delta-FeOOH surface even at neutral pH. The As(V) adsorption capacity of delta-FeOOH was estimated to be 37.3 mg g(-1), at pH 7. The kinetics data were best fitted with a pseudo-second order, thus suggesting chemical adsorption on the surface and pores of delta-FeOOH nanoparticles. The interaction between As(V) and delta-FeOOH nanoparticles was suggested to be mainly inner sphere complexes. The adsorption isotherm obtained at pH 7 was best fitted to the Langmuir and Redlich-Peterson models and, therefore, a non-ideal monolayer adsorption model for As(V) on delta-FeOOH nanoparticles was proposed. The small particle size, high surface area and adsorption capacity make delta-FeOOH a promising adsorbent for toxic metals in contaminated water. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.