Influence of pH, humic acid, ionic strength, foreign ions, and temperature on 60Co(II) sorption onto γ-Al2O3

The sorption of Co-60(II) on gamma-Al2O3 was conducted under various conditions, i.e., contact time, adsorbent content, pH, ionic strength, foreign ions, humic acid (HA), and temperature. Results of sorption data analysis indicated that the sorption of Co-60(II) on gamma-Al2O3 was strongly dependent on pH and ionic strength. At low pH the sorption was dominated by outer-sphere surface complexation or ion exchange, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The presence of different cation ions influenced Co-60(II) sorption, while the presence of different anion ions had no obvious influences on Co-60(II) sorption. The presence of HA decreased the sorption of Co-60(II) on gamma-Al2O3. The sorption isotherms were simulated well with the Langmuir model. The thermodynamic parameters (Delta H (0) , Delta S (0) and Delta G (0) ) calculated from the temperature-dependent sorption isotherms indicated that the sorption of Co-60(II) on gamma-Al2O3 was an endothermic and spontaneous process. Experimental results indicated that the low cost material was a suitable material in the preconcentration of Co-60(II) from large volumes of aqueous solutions.