Preparation and characterization of core-shell structured nanocomposite materials and their adsorption behavior on U (VI) from aqueous solutions

Mixed metal hydroxide nanoparticles SnAlFe (OH)(x) (SAF) was prepared via a rapid coprecipitation method and used in coating two different cores MnO2 and TiO2 to form MnO2@SAF and TiO2@SAF. The prepared adsorbents were characterized carefully by scanning electron microscopy/energy dispersive X-ray, transmission electron microscopy, atomic force microscope, X-ray diffraction, and Fourier transformed infrared spectroscopy. The prepared core-shell nanocomposites used as new adsorbents for U (VI) removal from aqueous solutions in a series of batch experiments. The effect of pH, contact time, initial U (VI) concentration, and temperature were investigated on U (VI) adsorption process. The results showed that the maximum adsorption capacities were 152.9 and 144.7 (mg/g) for MnO2@SAF and TiO2@SAF, respectively, with pH 7 and 293 K. The adsorption kinetics of U (VI) onto both prepared adsorbents followed pseudo-second order and intra-particle kinetic models. At the same time, the adsorption isotherms obeyed the Langmuir isotherm model. Thus, the kinetic and the isothermal data reveal the chemisorption of U (VI) on the prepared adsorbents. Thermodynamic parameters (Delta H degrees, Delta S degrees, and Delta G degrees) were calculated from the temperature-dependent adsorption data. The U (VI) adsorption process on the prepared adsorbents is endothermic and spontaneous. The results show that the adsorbent materials maintain removal efficiency during the first two cycles of the adsorption-regeneration cycle and then decrease slightly in the third cycle. The results indicate that the prepared adsorbents are potential and suitable candidates for U (VI) adsorption from aqueous solutions.