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

The low density CeO, PrO and NdO aerogels were synthesized by a novel solution-freeze-drying-calcination route. The bulk densities of the CeO, PrO and NdO aerogels were calculated to be 8.10, 10.67 and 9.80 mg/cm, 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 CeO, PrO and NdO 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 CeO 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).