In this study, we fabricated a new hybrid adsorbent, titania-silica binary oxide (TiO2-SiO2)-polyacrylonitrile (PAN), by loading nanosized sol-gel-derived TiO2-SiO2 onto a porous PAN polymer for enhanced arsenite [As(III)] and arsenate [As(V)] species removal from aqueous media. The resulting sorbent was characterized by thermogravimetric analysis, scanning electron microscopy, X-ray powder diffraction, IR spectroscopy, and porosity measurements. The sorption process for the removal of As(V) and As(III) was assessed with various parameters, including the effects of the pH, contact time, temperature, and existence of foreign competing ions. We found that the adsorption of As(III) and As(V) species onto TiO2-SiO2-PAN was dependent on the pH of solution, and it could be well represented by the Langmuir and Dubinin-Radushkevich isotherm models. The prepared hybrid adsorbent exhibited highly selective arsenic retention from water in the presence of Cl-, NO3-, NO2-, SO42-, and SO32- anions at much greater levels than those toxic metals examined. The values of the standard free energy, enthalpy, and entropy proved that the sorption of As(V) and As(III) species onto the hybrid adsorbent TiO2-SiO2-PAN was an endothermic and spontaneous process. All of the results validated the feasibility of TiO2-SiO2-PAN for the highly effective removal of As(V) and As(III) from contaminated waters. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 3495-3503, 2011