Effect of co-existing ions during the preparation of alumina by electrolysis with aluminum soluble electrodes: Structure and defluoridation activity of electro-synthesized adsorbents.
Résumé
The electrochem. dissoln. of Al was carried out to prep. hydrated aluminas which were characterized by SEM, energy dispersive spectroscopy (EDS), x-ray diffraction (XRD), chem. titrns. 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 soln., while aluminas synthesized in the other media contained a mixt. of phases, usually both boehmite and bayerite γ-Al(OH)3. All the boehmite phases contained nano-crystallites of \textless3 nm. Batch defluoridation expts. revealed a 2nd influence of the original electrolyte. Aluminas were very effective in defluoridation with abatement rates of 99.5, 98.5 and 97.3% from neutral F- solns. at 10 mg/L when they were prepd. in soln. of (NH4)2SO4, (NH4)HCO2 and NH4Cl, resp. The max. F- capacities were 46.94; 10.25 and 12.18 mg/g for aluminas prepd. in soln. of (NH4)2SO4; (NH4)HCO2 and NH4Cl, resp. The amt. of dissolved Al was \textless0.19 mg/L at neutral pH. These results show that a defluoridation with electro-synthesized aluminas would be more efficient and safe than a direct electrocoagulation. [on SciFinder(R)]