The electrochemical dissolution of aluminum was carried out to prepare hydrated aluminas which were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), chemical titrations and defluoridation activities. Aluminas were obtained at controlled pH depending upon the counter cations of the electrolyte. A boehmite AlOOH phase was isolated mainly in ammonium solution, while aluminas synthesized in the other media contained a mixture of phases, usually both boehmite and bayerite gamma-Al(OH)(3). All the boehmite phases contained nano-crystallites of less than 3 nm. Batch defluoridation experiments revealed a second influence of the original electrolyte. Aluminas were very effective in defluoridation with abatement rates of 99.5%, 98.5% and 973% from neutral fluoride solution at 10 mg L-1 when they were prepared in solution of (NH4)(2)SO4, (NH4)HCO2 and NH4Cl, respectively. The maximum fluoride capacities were 46.94; 10.25 and 12.18 mg g(-1) for aluminas prepared in solution of (NH4)(2)SO4; (NH4)HCO2 and NH4Cl, respectively. The amount of dissolved Al was found to be less than 0.19 mg L-1 at neutral pH. These results show that a defluoridation with electro-synthesized aluminas would be more efficient and safe than a direct electrocoagulation. (C) 2013 Elsevier B.V. All rights reserved.