60Co aqueous speciation and pH effect on the adsorption behavior on inorganic materials

The adsorption of radioactive cobalt from aqueous solution on MgO, MnO2, TiO2, SnO, activated carbon and calcined hydrotalcite was studied under static conditions as a function of pH (1, 3, 5, 7, and 10) of the Co-60 solution. It was found that under the experimental conditions, Co-60 was significantly adsorbed on MnO2, TiO2 and activated carbon and in smaller quantities on MgO, SnO and calcined hydrotalcite. The adsorption of Co-60 species on MgO, MnO2, TiO2 and SnO can be attributed to the direct exchange of ions with a specific group on the adsorbing surface, in accordance with the concept of zero point charge (zpc). The radionuclide content was determined by gamma-spectrometry. The Co-60 chemical species present in aqueous solutions with different pH values were surveyed by using high-voltage electrophoresis. It was also found that Co-60 was present only as a cationic species at pH 1, 3, 5 and 7 and a neutral species at alkaline pH. (c) 2005 Elsevier Ltd. All rights reserved.