Ion exchange studies of europium on uranium antimonate

Uranium antimonate (USb) has been prepared by the precipitation reaction between uranyl nitrate and potassium pyroantimonate and it has been characterized by X-ray diffraction (XRD), thermal analysis, energy disperse X-ray florescence, and pH titration. Ion exchange of europium on USb as a function of time, temperature, concentration of nitric acid and europium has been studied. The distribution coefficient of europium on USb was found to decrease from ∼105 ml g−1 at 0.05 M nitric acid to 22 ml g−1 at 2 M nitric acid. Uptake of europium was fitt to a particle diffusion equation and the diffusion coefficient (Di) was calculated from the slope of Bt–t plots. The energy (Ea) and entropy (ΔS∗) of activation for the sorption of europium were found to be 17 kJ mol−1 and −67.9 J mol−1 K−1, respectively. Sorption data obtained at various concentrations of europium were fitted into a Langmuir adsorption isotherm and the enthalpy change accompanied by the sorption of europium was determined by the temperature variation method.