Comparison of Adsorption Capacity of Natural and Acid-activated Kaolinite Clay for Cesium ions from Aqueous Solution

Objectives : This study is to compare the removal efficiency of cesium ions in aqueous solutions by natural and acid-activated kaolinite clay.Methods : Natural kaolinite clay was acid-treated with H2SO4 (2M) at 80oC for 6 h under mechanical stirring. While activating natural kaolinite clay with acid, cations such as Al3+, Ca2+, Mg2+ and Fe3+ were partially eluted from the crystal lattice of natural kaolinite clay, and resulted in the increase in the surface area and the pore volume through the opening of crystal lattice. The surface area and the pore volume of acid-activated kaolinite clay were found to be roughly three times higher than natural kaolinite clay. The characteristics of natural and acid-activated kaolinite clay were observed by X-ray Fluorescence Spectroscopy, Energy Dispersive X-ray Spectroscopy, and BET Surface Area Analyzer.Results and Discussion : Generally, adsorption efficiency of Cs+ ion by acid-activated kaolinite clay showed much higher compared with natural kaolinite clay. At 50 mg L-1 of Cs+ ion concentration and the unit of dose in g L-1 , the adsorption efficiencies of Cs+ ion by natural and acid-activated kaolinite clay were 57.5% and 96.9%, respectively. The data obtained from this study were fitted to the adsorption isotherm and the kinetic models, respectively. It revealed that the Langmuir isotherm and the pseudo-second-order kinetic models described well the adsorption behavior of Cs+ ions on both natural and acid-activated kaolinite clay owing to their higher correlation coefficient R2. Based on the Langmuir isotherm coefficient Q, adsorption capacity of Cs+ ion by natural kaolinite clay and acid-activated kaolinite clay were 5.65 mg g-1 and 10.6 mg g-1, respectively.Conclusion : The results demonstrated that acid-activated kaolinite clay with acid treatment can be used as more effective adsorbent for the adsorption of Cs+ ions from aqueous solution than natural kaolinite clay.