Radiotracer technique has been used to study the removal of Hg(II) ions from aqueous solutions by composite of polyaniline with polystyrene. This study reveals that the increase of adsorbent concentration (10(-8)-10(-3) M) and temperature (293-333 K) enhances the removal of Hg(II) ions. Concentration-dependence data agree well with the Freundlich isotherm. Thermochemical data show that this process is endothermic in nature. The radiation stability of the composite was also investigated by exposing it to a 11.1-GBq (Ra-Be) source associated with gamma dose of 1.72 Gy h(-1). Irradiation has practically no effect on the adsorption capacity of the composite. Desorption experiments show that the process of adsorption of mercury ions is almost irreversible and chemisorptive in nature. (C) 2003 Elsevier B.V. All rights reserved.