A Comparison of Adsorption, Reduction, and Polymerization of the Plutonyl(VI) and Uranyl(VI) Ions from Solution onto the Muscovite Basal Plane.
X-ray scattering techniques [in situ resonant anomalous X-ray reflectivity (RAXR) and specular crystal truncation rods (CTR)] were used to compare muscovite (001) surfaces in contact with solutions containing either 0.1 mM plutonyl(VI) or 1 mM uranyl(VI) at pH = 3.2 ± 0.2, I(NaCl) = 0.1 M, as well as in situ grazing-incidence X-ray absorption near-edge structure (GI XANES) spectroscopy and ex situ alpha spectrometry. Details of the surface coverage are found to be very different. In the case of Pu, alpha spectrometry finds a surface coverage of 8.3 Pu/AUC(AUC= 46.72 Å2, the unit cell area), far in excess of the 0.5 Pu/AUCexpected for ionic adsorption of PuO22+. GI XANES results show that Pu is predominantly tetravalent on the surface, and the CTR/RAXR results show that the adsorbed Pu is broadly distributed. Taken together with previous findings, the results are consistent with adsorption of Pu in the form of Pu(IV)-oxo-nanoparticles. In contrast, uranyl shows only negligible, if any, adsorption according to all methods applied. These results are discussed and compared within the context of known Pu and U redox chemistry.
Institute of Resource Ecology, Helmholtz-Zentrum Dresden-Rossendorf , Dresden 01314, Germany.
Stefan
S
Hellebrandt
Chemical Sciences and Engineering Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.
Sang Soo
SS
Lee
Chemical Sciences and Engineering Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.
Karah E
KE
Knope
Department of Civil & Environmental Engineering & Earth Sciences, University of Notre Dame , Notre Dame, Indiana 46556, United States.
Aaron J
AJ
Lussier
Center for Advanced Radiation Sources, University of Chicago , Chicago, Illinois 60637, United States.
Joanne E
JE
Stubbs
Center for Advanced Radiation Sources, University of Chicago , Chicago, Illinois 60637, United States.
Peter J
PJ
Eng
Chemical Sciences and Engineering Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.
L
L
Soderholm
Chemical Sciences and Engineering Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.
Paul
P
Fenter
Institute of Resource Ecology, Helmholtz-Zentrum Dresden-Rossendorf , Dresden 01314, Germany.
Moritz
M
Schmidt