In order to synthesize a self-organized, TiO2 nanotubular layer for wastewater purification, anodizations were performed at constant applied potential in hydrofluoric acid and the anodic TiO2 layer was heat treated. The anodic nanotube arrays were also influenced by the applied anodic potentials and HF concentrations. The anodic TiO2 nanotubular structured film with various morphologies and crystal structures can be synthesized by proper electrochemical anodization and additional annealing treatment. The photocatalytic efficiencies were maximized for the anatase-type, TiO2 nanotubular layer which was prepared by annealing at 550 degrees C. (c) 2008 Elsevier B.V. All rights reserved.