Sorption Behavior of Am-241, Eu-152, Tb-160 and Co-60 in the Geological Materials: Eu as an Optimum Analogue for Fate and Transport of Am Behavior in Subsurface Environment

Rare earth elements(REEs) have been used as an useful tool in understanding the various geological processes such as evolution and differentiation in the crust. The REEs also have been used as an analog of actinides for radioactive wastes at the water-rock interactions. Using physicochemical properties of the REEs and actinides, we have shown that Eu is an optimum analogue for understanding the behavior of Am in subsurface environments. Factors affecting sorption behavior of radioactive nuclides in groundwater were investigated by batch experiments. Four nuclides such as Am-241, Eu-152, Tb-160, and Co-60 were selected to test our hypothesis, and Tb-160 and Co-60 were specifically used to compare to the sorption behavior between Am-241-Eu-152 and other radioactive nuclides. Four different rock samples and one groundwater were used in the batch experiments where solution pH for all experiments was fixed at 5.5. Our results demonstrate that Am-241, Eu-152, and Tb-160 show similar sorption behavior whereas Co-60 is different in sorption behavior at the mineral-water interface, suggesting that the sorption behavior of Co-60 is affected by different rock types. Our results also show that 1) Eu in REEs is optimum analogue of fate and transport of Am in subsurface environments, and 2) mineral compositions such as SiO2, TiO2, P2O5 and distribution of REEs such as Eu anomaly play key roles in affecting sorption behavior of radioactive nuclides even though physicochemical properties of geological materials such as specific surface area and cation exchange capacity can not be ruled out.