The foam-type polyurethane (PU) ion exchangers were synthesized by the UV radiation-induced graft copolymerization of acrylic acid (AAc) onto PU. We studied the degree of grafting relative to the synthetic conditions, such as the reaction time and temperature and the AAc and benzophenone (BP) concentrations. The structures of the PU-g-AAc ion exchangers were determined by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and elemental analysis (EA). The maximum degree of grafting (26.85%) was obtained at a reaction temperature of 50 ℃ and under a UV radiation intensity of 450 W. The swelling ratio and ion exchange capacity of the PU-g-AAc ion exchangers were 4.21 and 2.25 meq/g respectively, at the maximum degree of grafting. The highest amount of NH₃ adsorbed was 48 mg/g at an ion exchange capacity of 2.25 meq/g. The NH₃ adsorption amount increased linearly as the initial concentrantion of NH₃ increased.