Removal of Cesium and Strontium from Aqueous

Abstract

Sorption of radioisotopes onto a stable colloidal phase may significantly enhance their transport in groundwater. The adsorption of cesium (Cs+) and strontium (Sr++ ) 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 (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) of adsorption were also calculated for each cation. These parameters showed that the adsorption of Cs+ and Sr++ onto NB 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.