First Synthesis of Uranyl Aluminate Nanoparticles

This paper describes, for the first time, a simple method for the synthesis of uranyl aluminate (URAL) nanoparticles. URAL was prepared by U(VI) hydrolytic precipitation with ammonia at pH = 11 in the presence of mesoporous alumina MSU-X under 20 kHz of sonication followed by annealing of the obtained solids at 800 C. TEM, XAFS, powder XRD, and 27Al MAS NMR studies revealed that the speciation of uranium in this system strongly depends on uranium concentration. The sample with 5 wt % of uranium yields air-stable nanoparticles (∼5 nm) of URAL. Presumably, UO2 2þ cations in this compound are coordinated with bidentate AlO2 - groups. The increase of uranium concentration to 30 wt % causes mostly formation of U3O8 fine particles (∼50 nm) and small amounts of URAL.