Metal oxide aerogels: Preparation and application for the uranium removal from aqueous solution

Abstract The low density CeO2, Pr2O3 and Nd2O3 aerogels were synthesized by a novel solution-freeze-drying-calcination route. The bulk densities of the CeO2, Pr2O3 and Nd2O3 aerogels were calculated to be 8.10, 10.67 and 9.80 mg/cm3, respectively. Moreover, the structure of metal oxide aerogels was similar due to the same template materials, which made them possible to be appealing materials for adsorption. The maximum adsorption capacity for U(VI) of the CeO2, Pr2O3 and Nd2O3 aerogels reached 481.5, 840.6 and 587.3 mg/g (pH = 7, T = 25 °C), respectively, which were much higher than most of other modified metal oxides. Moreover, at low concentration of U(VI) (5 mg/L), it was completely dislodged by CeO2 aerogel and the remaining U(VI) was below 0.006 mg/L, which was lower than the effluent standards of United States Environmental Protection Agency and World Health Organization. Besides, after five cycles, the adsorption efficiency of metal oxide aerogels almost remained at a high level. Due to the excellent adsorption performance and high reusability, the three metal oxide aerogels would be promising adsorbents for the removal of U(VI).