Arsenate and arsenite typically co-exist in groundwater. Arsenite is more toxic than arsenate, while it is more difficult to be removed than arsenate. In order to effectively remove arsenate and arsenite simultaneously from water solution, a nanostructured zirconium-manganese binary hydrous oxide was successfully developed in this study. The amorphous sorbent was aggregate of nanoparticles with a high surface area of 213 m(2) g(-1). Our sorption experiments showed that the nano-scale particles could effectively oxidize As(III) to As(V) and greatly remove both As(V) and As(III). The maximal adsorption capacities of As(V) and As(III) were 80 and 104 mg g(-1) at pH 5.0, respectively. As(V) uptake may be mainly achieved through replacement of hydroxyl groups and sulfate anions on the surface of the oxide and formation of inner complexes. The As(III) removal was essentially due to a sorption coupled with oxidation process; the MnO2 was mainly responsible for oxidization of As(III) to As(V) that was subsequently adsorbed onto ZrO2. (C) 2012 Elsevier Inc. All rights reserved.