Ion Diffusion in Compacted Sodium and Calcium Bentonites

摘要

The diffusivities of Sr exp 2+ and Cs exp + in compacted Erbsloeh Ca-bentonite and Mx-80 Na-bentonite have been determined by various tracer techniques. Whereas the diffusivity of Sr exp 2+ was found to be (1,5(2))x10 exp -11 m exp 2 xsec exp -1 in both bentonites the diffusivity of Cs exp + was found to be (7(2))x10 exp -13 and (2,5(5))x10 exp -12 m exp 2 xsec exp -1 in erbsloeh and Mx-80 respectively. A comparison of the diffusivities of Sr exp 2+ and Cs exp + with the diffusivities of Cl exp - and I exp - earlier obtained shows that high Ksub (d)-values are not necessarily an indication of immobilization i.e. a simple pore diffusion model with retardation of the diffusing ions by sorption processes is not valid for Sr exp 2+ and Cs exp + . Water ratio (density) and homogenization time were not found to have any measurable effect on the diffusivity of the cations. (Atomindex citation 14:729337)