Tritium redistribution between water and clay minerals

Hydrogen-isotope exchange between clay minerals and tritiated water was studied with kaolinite, montmorillonite and palygorskite. At all possible positions, tritium accumulated most intensively during the initial stage (10 to 20 days) but further increase of tritium concentration in experimental systems was much less intensive. Interaction of tritiated water with clay minerals decreased in a similar manner. In all samples, the highest amounts of tritium atoms and the maximum accumulation rates (V) were observed in the surface-adsorbed water (V_surf) over the complete study period. The modes of tritium accumulation in the interlayer space (montmorillonite) and in the channels (palygorskite) (V_inter) are quite similar and both types of structures are very suitable for hydrogen-isotope exchange. Availability of well-developed paths for the access of T⁺ ions to structural OH-groups (V_struct) enables intense tritium accumulation at these positions in montmorillonite and palygorskite (V_inter  V_struct). In kaolinite the access of T⁺ ions to structural OH-groups is more difficult, in spite of the considerable number of potential exchange positions in its structure, therefore resulting in lower tritium adsorption in comparison with the other two clay minerals.