Adsorption of Cs(I), Sr(II) and Co(II) on Al2O3

The sorption of Cs(I), Sr(II) and Co(II) from aqueous solutions on alumina under various experimental conditions has been studied by batch techniques. Freundlich, Langmuir and Dubnin-Raduskevich equations have been used to interpret the sorption data. The values of various thermodynamic parameters have been determined. The sorption of Cs(I) and Sr(II) on alumina is exothermic in nature while that of Co(II) is an endothermic process. The H ^o values for Cs(I), Sr(II) and Co(II) were–23.29 KJ/mol at 298K,–35.3 KJ/mol at 293 K and 13.49 KJ/mol at 293 K, respectively. Negative values of G ^o show the spontaneity of the sorption processes; G ^o values of Cs(I) and Sr(II) becomes less negative at higher temperatures while the G ^o values of Co(II) become more negative with increasing temperature. At higher temperatures, less amounts of Cs(I) and Sr(II) and greater amounts of Co(II) are sorbed on alumina. The values of the mean free energies of sorption,E, for Sr(II) and Co(II) at various temperatures were within the range of 7–10 KJ/mol which show that these metals are sorbed on alumina predominantly by an ion-exchange process.