The present work concerns an equilibrium study of naturally occurring clinoptilolite as an ion-exchange medium; the clinoptilolite has been used for the removal of the NW ion from a model aqueous effluent of the Landfill Leachate Assisted Froth Flotation (LLAFF) process. The other principal cations involved were sodium and calcium, and the anion was chloride. A number of experimental tests with constant ionic strength in solution were conducted; these were performed to further validate the feasibility of using clinoptilolite, to remove NH4+ ion from the LLAFF effluent. The experimental data obtained were well described by the law of mass action. A binary-component equilibrium study revealed a value for the binary separation factor alpha(NH4 +,Na +) of 5.5; this value was relatively unaffected by the total salinity under the experimental conditions. Values for the intra-particle diffusion coefficient and the maximum ion-exchange capacity were also obtained; the latter was affected by total salinity. Results from the binary-component and multicomponent studies have revealed the selectivity of clinoptilolite for ammonium over other cations under the compositional conditions of the model LLAFF effluent: The selectivity sequence is K+>NH4+>Na+>>Ca2+. The factors that influence the selectivity of clinoptilolite for NH4+ in LLAFF effluent have been ascertained; in particular, it has been found that small quantities of Ca2+ in the effluent have a deleterious effect on both selectivity toward ammonium and ammonium ion-exchange capacity.