| Abstract
| - We report here the hydrothermal synthesis of a MCM-48 mesoporous silicate phase containing uranium. The characterization of these materials by multiple techniques confirmed the incorporation of uranyl groups into the silicate framework, leading thereby to an increase in the unit cell parameter and the pore size of the host material. On calcination, the formation of nanoparticles of α-U3O8 is observed in the samples containing higher loading of uranium. The loading of uranium also gave rise to a multi-pore mesoporous system in the host matrix.
- MCM-48 samples containing uranium (U−MCM-48) to the extent of 1 to 6 wt % weresynthesized hydrothermally and characterized using powder XRD, 29Si MAS NMR, FTIRspectroscopy, DR UV−Vis spectroscopy, N2 sorption, and TEM techniques. These analysesconfirmed the formation of an ordered cubic-phase MCM-48 mesomaterial where the uraniumexisted in the hexavalent state forming a local uranate type structure. A part of the uranylgroups were found to be incorporated in the framework positions, while the rest wereanchored on to the wall of the host silica matrix. Also, the U−MCM-48 samples exhibitedan enlargement of the cubic cell unit as well as an increase in the degree of cross-linking,as revealed by XRD and MAS NMR results. The samples exhibited N2 sorption isotherms oftype IV and an increase was observed in the pore diameter as a result of uraniumincorporation. TEM investigation revealed that although U−MCM-48 samples were of cubicsymmetry similar to that of Si−MCM-48, some distortion in the pore structure was clearlynoticeable. Furthermore, in case of the samples with U loading of ∼6 wt %, formation ofnanocrystallites of α-U3O8 was also detected after calcination and such samples consistedof a multiple-size pore system.
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