The capacity of a calcined hydrotalcite and a natural zeolite to remove U(VI) chemical species from both acidic and basic aqueous systems has been investigated. The U(VI) uptake by the calcined hydrotalcite and the natural zeolite was determined to be from 5 to 200 mu molmL(-1) and from 2 to 10 mu molmL(-1), respectively. Uranium was measured using UV-Vis spectroscopy in the remaining solutions. The U(VI) adsorption of both materials was higher in the acidic aqueous system. Independent of the pH of the aqueous media, the [UO2(CO3)(3)](4-) species play an important role in the regeneration of the original crystalline structure of the HT.