Sorption of ammonium cation on H⁺ and Na⁺ modified high silicon natural  zeolites – clinoptilolite, mordenite  and  synthetic cationite  KU-2-8 – for the purpose of estimating perspectivity of their application to purifying sewage from aluminium nitrogen, has been investigated. Thermodynamic parameters and constants of ion exchange equilibrium have been calculated. It is established that a value of absorption  exchange capacity (AEC) at extraction of ammonium ions from solution with their low concentration on almost approaches to the values of  AEC for  H- and Na-KU-2-8 that affords possibility of recommending the cheap and available natural  zeolites instead of expensive synthetic sorbent KU-2-8.