The use of Y zeolite and erionite to remove UO2(2+) ions from aqueous solutions has been investigated. The effect of temperature, the concentration of UO2(2+) uptake, the diffusion coefficients, and the ion-exchange isotherms were also studied. X-ray diffraction, thermal analyses, and transmission electron microscopy were used to characterize the solids. The UO2(2+) content was determined by neutron activation analysis. The diffusion coefficients are not clearly affected by temperature or concentration. They definitely depend on the structure of each zeolite. The UO2(2+) exchange capacities were 0.2037 and 0.7345 meq UO2(2+)/g for erionite and Y zeolite, respectively. It was found that UO2(2+) is exchanged with the cations of the large cavity in Y zeolite. In the case of erionite, UO2(2+) is exchanged with the cations localized in sites where the charge densities are very high.