A Comparison of Adsorption, Reduction, and Polymerization of the Plutonyl(VI) and Uranyl(VI) Ions from Solution onto the Muscovite Basal Plane

Abstract

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/A (A = 46.72 Å, the unit cell area), far in excess of the 0.5 Pu/A expected for ionic adsorption of PuO. 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.

Formation and Aggregation of ZrO2 Nanoparticles on Muscovite (001)

“…17 Nanoparticle formation via hydrolysis has also been found to be an important process in the chemical and environmental behavior of highly radiotoxic Pu, 18,19 where it was found that the process is accelerated at mineral surfaces. 20,21 Aqueous Zr(IV) polymerization then is a promising model system for studying such multistep nanoparticle evolution processes, since Zr(IV), bearing a small ionic radius (0.75 Å) and high charge, is prone to hydrolysis in solutions leading to a progressive oligomerization that produces polydisperse Zr nanoparticles. Numerous studies have focused on Zr(IV) hydrolysis and oligomerization reactions in aqueous solutions to gain insights into the structural details of potential Zr(IV) building units as a function of solution chemistry using a variety of techniques, including X-ray absorption fine structure (XAFS) spectroscopy, 22−25 small (or wide)-angle X-ray scattering [S(W)AXS], 26−31 high-energy X-ray scattering (HEXS), 3 NMR/Raman spectroscopy, 3,23,32 electron-spray ionization mass spectrometry (ESI-MS), 25,33,34 dynamic light scattering (DLS), 24,35 transmission electron microscopy (TEM), 36 and Xray diffraction (XRD).…”

“…One component of such a system may be the formation of nanoparticles through the polymerization of metal cation hydrolysis species by olation () or oxolation (). The hydrolysis route as a facile pathway to the formation of nanoparticles has been demonstrated in recent work on Ce­(IV) . Nanoparticle formation via hydrolysis has also been found to be an important process in the chemical and environmental behavior of highly radiotoxic Pu, , where it was found that the process is accelerated at mineral surfaces. , …”

Intensive study on structure transformation of muscovite single crystal under high-doseγ-ray irradiation and mechanism speculation

“…Vacancy shows as a dioctahedral structure in the octahedron sheet. Normally, the tri-layer structure is linked together by K þ ion via weak ionic bonds [50][51][52][53]. For strong assemblage of adjacent layers, it is non-expandable.…”

Intensive evaluation of radiation stability of phlogopite single crystals under high doses of γ-ray irradiation

“…Normally, partial Si atoms within the tetrahedron are substituted by Al atoms, yielding negative charges. 3 In order to balance these negative charges, partial cations such as K + or Na + ions exist in the interlayer, leading to an uneven distribution of charges. 3 In addition, a layered structure has numerous cavities trapping other species such as Fe 3+ or Fe 2+ ions, enhancing the uneven distribution of charges.…”

“…3 In order to balance these negative charges, partial cations such as K + or Na + ions exist in the interlayer, leading to an uneven distribution of charges. 3 In addition, a layered structure has numerous cavities trapping other species such as Fe 3+ or Fe 2+ ions, enhancing the uneven distribution of charges. In most of these cases, the interlayer only exudes the van der Waals force, resulting in the facile movement of the adjacent layers.…”