Am³⁺ and Eu³⁺/alkali cation exchange selectivity on mordenite and zeolite L

Am³⁺ and Eu³⁺/alkali cation exchange selectivity was studied on mordenite and zeolite L at 25 to 60 °C to examine the effect of their openings of ion-exchange sites. The corrected selectivity coefficient at the infinitesimal exchange increased in the order of Eu³⁺ < Am³⁺ on mordenite and Am³⁺ < Eu³⁺ on zeolite L. The selectivity reversal did not reflect the effect of the ionic form, but reflected the dimension of the opening of the ion-exchange site and charge of trivalent cations, since the crystal ionic radii of alkali cations were much smaller than the openings of these zeolites (7-8 Å).