Isotopic exchange between zeolites CaY 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 data were described by:

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

M.Guilloux, P.Fouilloux, P.Bussiere: Journal of Inorganic and Nuclear Chemistry, 1975, 37[10], 2211–5