In this study, the photocatalytic oxidation of hazardous arsenite (As(III)) to arsenate (As(V)) and the sequential removal of arsenate from aqueous solution by liquid-phase polymer-based retention (LPR) were investigated. The photocatalytic oxidation of arsenite was performed using TiO2 (P25 Degussa, Germany) under UV-A light. The optimal photocatalytic conditions to oxidize 10 mg L-1 of arsenite solution were achieved using a 0.5 g L-1 of catalyst at a pH value of 2. The As(III) oxidation reached 100% after 30 min of illumination with UV-A light. A water-soluble polymer containing quaternary ammonium groups, poly(3-acrylamidopropyl) trimethylammonium chloride (P(ClAPTA)), was used as an extracting reagent in the LPR process. To obtain the optimized conditions, the removal experiments were performed at various polymer : As(V) molar ratios using 10 mg L-1 of arsenate solutions. After the oxidation of As(III) to As(V), the removal of arsenate by P(ClAPTA) was obtained in a 99% yield using a 20 : 1 polymer : As(V) molar ratio at a pH value of 9. The results demonstrate that the combination of these methods is highly useful for potential applications related to the treatment of wastewater contaminated with As(III). (C) 2014 Wiley Periodicals, Inc.