Comparative of 90Sr and 241Am Migration on Unsaturated Silty Clay Medium

Abstract

The studies on the batch experiments and transport of 90Sr and 241Am were respectively conducted under unsaturated flow conditions in silty clay column. The results show that the linear correlation coefficient r2 of adsorption and desorption isotherms for 90Sr and 241Am in silty clay medium is greater than 0.9, which indicates that the Freundlich isotherm adsorption model can better describe the adsorption and desorption process of different nuclides in silty clay. The adsorption capacity of strongly adsorbed nuclides 241Am is much greater than that of 90Sr. As for 90Sr, the first-order rate coefficient(named as β) between the dissolved phase and the adsorbed phase was considered in the non-equilibrium adsorption model by transport column. The calculated concentration distribution curve is good agreement with the measured values. The fitting results show that the distribution coefficient(named as Kd) and β of 90Sr in the fine sand aquifer are 3.6 mL/g and 0.55/h. Respectively, in terms of 241Am, the radionuclides concentration distribution curves in equilibrium adsorption model and non-equilibrium adsorption model are in good agreement with the measured values. It shows that the stronger adsorption capacity of the nuclides have the faster rate of the adsorption-desorption in the soil, meanwhile the shorter time for the system reaction equilibrium. At this time, the fitting results of the equilibrium adsorption mode and the non-equilibrium adsorption model are closer to each other. Meanwhile the calculated Kd value by equilibrium adsorption model is 3×103 mL/g.

Keywords

• radionuclide
• irreversible adsorption
• migration
• non-equilibrium mode