Adsorption characteristics of cobalt on ZrO2 and Al2O3 adsorbents in high-temperature water

To evaluate adsorbents for the removal of soluble corrosion products, mainly Co-60 under PWR reactor coolant conditions, ZrO2 and Al2O3 were prepared by the sol-gel method and hydrolysis of metal alkoxide, respectively. Their structures were studied by x-ray diffractometer and TG-DTA. The Co2+ adsorption on ZrO2 and Al2O3 in high-temperature water were investigated in a stirred hatch autoclave. The effect of calcination temperature on Co2+ adsorption capacity of ZrO2 and Al2O3, the effect of pH on Co2+ adsorption capacity of Al2O3, the effect of adsorption temperature on adsorption capacity and Co2+ adsorption isotherms were studied. The prepared ZrO2 and Al2O3 adsorbents were found to be stable with tetragonal, monoclinic structures and theta, delta, and alpha phase structures, respectively. The enthalpy changes (DeltaH degrees) due to the adsorption of Co2+ on ZrO2 and Al2O3 were 12.8 and 16.1 kJ/gmol, which suggest that the adsorption is an irreversible endothermic reaction in the experiment temperature (150 similar to 250 degreesC). The Co2+ adsorption capacities of ZrO2 and Al2O3 at 250 degreesC were 0.16 and 0.18 meq Co2+/g adsorbent, respectively. The thermodynamic function of adsorption of DeltaH, DeltaS, DeltaG, and equilibrium constant K-d were calculated. The process of adsorption was established to be endothermic, and chemisorption was stabilized through thermodynamic functions.