Isotopic exchange between zeolites CaY and Ce(III)Y and aqueous solutions of the cations appeared to be controlled by solid diffusion. Following isothermal investigation at 0 to 65C, it was found that this process took place in two stages, the second one being rather slow, and this provided a means for calculating the activation energies. The diffusivities of Ca2+ and Ce3+ at 38C were 6.5 x 10-19 and 1 x 10-19m2/s, respectively, and the overall data were described by:

Ca2+:     D(m2/s) = 2.6 x 100exp[-57.0(kJ/mol)/RT]

Ce3+:     D(m2/s) = 1.2 x 10-4exp[-85.0(kJ/mol)/RT]

Etude de l'Echange Isotopique des Zeolithes CaY et Ce(III)Y avec les Ions Ca2+ et Ce3+ en Solution: I - Solutions Aqueuses. M.Guilloux, P.Fouilloux, P.Bussiere: Journal of Inorganic and Nuclear Chemistry, 1975, 37[10], 2211–5