Ceramics-Silikáty 40, (2) 61 - 66 (1996)

Cation-exchange reactions between NH₄⁺ saturated zeolites and solutions containing essential cations occurring as main cations in natural soil solutions (K⁺, Na⁺, Ca²⁺, Mg²⁺) were studied. Natural clinoptilolite and two synthetic zeolites (PC and phillipsite) prepared by hydrothermal alteration of power station fly ashes were used as zeolites and saturated with NH₄⁺ in a NH₄Cl solution (c = 5 mol.l⁻¹). K⁺ and Ca²⁺ yielded the best cation-exchange in the case of all three zeolites. The equilibrium isotherms of ion-exchange reactions were measured in concentration limits usual for real soil solutions. The obtained results indicate that the NH₄⁺ ions might be relatively quickly released to the soil solution after the application of NH₄⁺ saturated zeolites to the soil. The exchange occurs preferably with K⁺ ions (and also with Ca²⁺ in the case of the PC zeolite) present in the soil solution.