Physicochemical and Separation Studies of some Lanthanides and some Coexisting Elements of Nuclear Significance from Various Sources

Abstract

Samples of zirconium titanium phosphate (ZTP) inorganic ion exchangers were locally synthesized, with different Zr: Ti mole ratios 95:5, 75:25, 25:75 and 5:95, as well as ceric tungstate (CeW). The samples were characterized using FT-IR, X-ray-diffraction (XRD), scanning electron microscopy (SEM) and pore sizer. The adsorption behavior of lanthanide elements, Ce(III), Tb(III) and Yb(III) traced by their corresponding radioactive isotopes 141Ce(III), 160Tb(III) and 169Yb(III) was studied under static conditions. The influence of some parameter: such as V/m (mL.g-1), solution pH, contact time, particle size, metal ion concentration and temperature on the adsorption kinetics were intensively studied in this work. The obtained data have shown that the adsorption is controlled by particle diffusion in each case. The calculated diffusion coefficients of all studied lanthanide ions have values in the range of 10-14 m2.s-1 which indicated that the sorption has a chemisorption nature. The percentage uptake values have generally the sequences Tb˃Yb˃ Ce. This result may suggest the adsorption of Yb as partially hydrated ions in contrast to Tb and Ce where dehydrated ions are adsorbed in the case of Tb(III) and Ce(III). Thermodynamic parameters such as changes in Gibbs free energy (∆G◦), enthalpy (∆H◦) and entropy (∆S◦) were calculated. The isotherms and kinetics of the adsorption process were analyzed using different models. The adsorption was found to follow Langmuir isotherm better than Freundlich and that the pseudo-second order kinetic fits the adsorption data.