Sorption of radioisotopes onto a stable colloidal phase may significantly enhance their transport in groundwater. The adsorption of cesium （Cs＋） and strontium （St^＋＋ ） from aqueous solutions onto commercial nat...Sorption of radioisotopes onto a stable colloidal phase may significantly enhance their transport in groundwater. The adsorption of cesium （Cs＋） and strontium （St^＋＋ ） from aqueous solutions onto commercial natural bentonite （NB） was studied as a function of contact time, temperature, bentonite mass and bentonite treatment （washing and heat treatment） on the uptake of these cations, independently. The heat treatment was 700 ℃ and washed bentonite samples termed by CB and WB respectively. Batch experiments results showed that the adsorptive capacity of NB at 293,298 and 308 K for Cs^＋ and Sr^＋＋ were 110,105, 104 and 35, 33.6, 31.8 mg/g respectively. The experimental results for strontium adsorption 293, 298 and 308 K fit well to a Langmuirian and Frendlich type isotherm but cesium adsorption fit better with Langmuir than Frendlich isotherm. Thermodynamic functions, the change of free energy （△G°）, enthalpy （△H°） and entropy （AS°） of adsorption were also calculated for each cation. These parameters showed that the adsorption of Cs^＋ and Sr^＋＋ onto N B was feasible, spontaneous and exothermic. The adsorption of Sr^＋＋ and Cs^＋ increases with increasing pH （pH 2-8） and follows pseudo-second order kinetics reaching equilibrium after an equilibration time of 300 and 5 min respectively. The adsorbed amount of Cs^＋ not affected by washing of NB but affected by the heat treatment. However the adsorbed amount of Sr^＋＋ on WB was higher than NB and CB.展开更多
文摘Sorption of radioisotopes onto a stable colloidal phase may significantly enhance their transport in groundwater. The adsorption of cesium （Cs＋） and strontium （St^＋＋ ） from aqueous solutions onto commercial natural bentonite （NB） was studied as a function of contact time, temperature, bentonite mass and bentonite treatment （washing and heat treatment） on the uptake of these cations, independently. The heat treatment was 700 ℃ and washed bentonite samples termed by CB and WB respectively. Batch experiments results showed that the adsorptive capacity of NB at 293,298 and 308 K for Cs^＋ and Sr^＋＋ were 110,105, 104 and 35, 33.6, 31.8 mg/g respectively. The experimental results for strontium adsorption 293, 298 and 308 K fit well to a Langmuirian and Frendlich type isotherm but cesium adsorption fit better with Langmuir than Frendlich isotherm. Thermodynamic functions, the change of free energy （△G°）, enthalpy （△H°） and entropy （AS°） of adsorption were also calculated for each cation. These parameters showed that the adsorption of Cs^＋ and Sr^＋＋ onto N B was feasible, spontaneous and exothermic. The adsorption of Sr^＋＋ and Cs^＋ increases with increasing pH （pH 2-8） and follows pseudo-second order kinetics reaching equilibrium after an equilibration time of 300 and 5 min respectively. The adsorbed amount of Cs^＋ not affected by washing of NB but affected by the heat treatment. However the adsorbed amount of Sr^＋＋ on WB was higher than NB and CB.
