Acrylamide-maleic acid (AAm-MA) hydrogels were prepared by gamma-irradiation of their aqueous solutions. UO2+2 ion uptake on P(AAm-MA) hydrogels was investigated using two types of gel systems prepared by a simple irradiation method and a prestructured reaction. It has been observed that gels prestructured with UO2+2 ions adsorbed approximately 15-20% more UO2+2 ions than gels prepared in pure water (the usual method). It was also found that the uranyl ion adsorption capacity of hydrogels increased with an increasing amount of maleic acid in the gel system and an increasing concentration of uranyl ion in the solution. A possible interaction mechanism between the groups in the copolymeric gels and UO2+2 ion has been proposed based on the stoichiometry and the spectroscopic evidence. (C) 2000 John Wiley & Sons, Inc.