Modeling the transport of cesium in crushed granite with empirical and reactive sorption models

The migration and retardation of radionuclides in the subsurface pose an important issue on the determination of waste disposal sites and the remediation of contaminated areas. Preliminary studies on identifying both physical and chemical characteristics that can affect the transport of radionuclides are necessary before conducting any engineering activities. This study focused on simulating the transport of cesium in crushed granite with sorption/desorption reactions. Both empirical and reactive sorption models were employed to describe batch and column experiments. Parameters of three empirical sorption models, including linear, Freundlich, and Langmuir were determined by fitting batch experimental data. Reaction constants of reactive sorption models were obtained from thermodynamic database or by fitting batch experiments. Breakthrough curves (BTCs) of column experiments were then simulated with both empirical and reactive sorption models to examine models' performance. We found that none of three empirical models can adequately describe the sorption/desorption kinetics of cesium, and neither equilibriumnor kinetic-controlled single-site sorption model seemed to rightly picture the BTCs. It was then suspected that at least two sorption reactions of different rates would contribute to the overall sorption reaction. Further attempts of using mixed equilibrium/kinetic and two-sites kinetic sorption models provide a better fit to column experiment data. Copyright ASCE 2004.