Identifying critical features of iron phosphate particle for lithium preference.

One-dimensional (1D) olivine iron phosphate (FePO) is widely proposed for electrochemical lithium (Li) extraction from dilute water sources, however, significant variations in Li selectivity were observed for particles with different physical attributes. Understanding how particle features influence Li and sodium (Na) co-intercalation is crucial for system design and enhancing Li selectivity. Here, we investigate a series of FePO particles with various features and revealed the importance of harnessing kinetic and chemo-mechanical barrier difference between lithiation and sodiation to promote selectivity.

Reaction Layer Formation on MgO in the Presence of Humidity.

Mineralization by MgO is an attractive potential strategy for direct air capture (DAC) of CO due to its tendency to form carbonate phases upon exposure to water and CO. Hydration of MgO during this process is typically assumed to not be rate limiting, even at ambient temperatures. However, surface passivation by hydrated phases likely reduces the CO capture capacity.

Y(III) Sorption at the Orthoclase (001) Surface Measured by X-ray Reflectivity.

Interactions of heavy metals with charged mineral surfaces control their mobility in the environment. Here, we investigate the adsorption of Y(III) onto the orthoclase (001) basal plane, the former as a representative of rare earth elements and an analogue of trivalent actinides and the latter as a representative of naturally abundant K-feldspar minerals. We apply in situ high-resolution X-ray reflectivity to determine the sorption capacity and molecular distribution of adsorbed Y species as a function of the Y concentration, [Y], at pH 7 and 5.

Structure and Surface Complexation at the Calcite(104)-Water Interface.

Calcite is the most stable polymorph of calcium carbonate (CaCO) under ambient conditions and is ubiquitous in natural systems. It plays a major role in controlling pH in environmental settings. Electrostatic phenomena at the calcite-water interface and the surface reactivity of calcite in general have important environmental implications.

Nanoscale oxygen defect gradients in UO surfaces.

Oxygen defects govern the behavior of a range of materials spanning catalysis, quantum computing, and nuclear energy. Understanding and controlling these defects is particularly important for the safe use, storage, and disposal of actinide oxides in the nuclear fuel cycle, since their oxidation state influences fuel lifetimes, stability, and the contamination of groundwater. However, poorly understood nanoscale fluctuations in these systems can lead to significant deviations from bulk oxidation behavior.

In situ structural study of the surface complexation of lead(II) on the chemically mechanically polished hematite (11¯02) surface.

A structural study of the surface complexation of Pb(II) on the (11¯02) surface of hematite was undertaken using crystal truncation rod (CTR) X-ray diffraction measurements under in situ conditions. The sorbed Pb was found to form inner sphere (IS) complexes at two types of edge-sharing sites on the half layer termination of the hematite (11¯02) surface. The best fit model contains Pb in distorted trigonal pyramids with an average PbO bond length of 2.

Quantifying small changes in uranium oxidation states using XPS of a shallow core level.

The U 4f line is commonly used to determine uranium oxidation states with X-ray photoelectron spectroscopy (XPS). In contrast, the XPS of the shallow core-levels of uranium are rarely recorded. Nonetheless, theory has shown that the U 5d (and 5p) multiplet structure is very sensitive to oxidation state.

Oxidative Corrosion of the UO (001) Surface by Nonclassical Diffusion.

Uranium oxide is central to every stage of the nuclear fuel cycle, from mining through fuel fabrication and use, to waste disposal and environmental cleanup. Its chemical and mechanical stability are intricately linked to the concentration of interstitial O atoms within the structure and the oxidation state of U. We have previously shown that, during corrosion of the UO (111) surface under either 1 atm of O gas or oxygenated water at room temperature, oxygen interstitials diffuse into the substrate to form a superlattice with three-layer periodicity.

Dynamic Stabilization of Metal Oxide-Water Interfaces.

The interaction of water with metal oxide surfaces plays a crucial role in the catalytic and geochemical behavior of metal oxides. In a vast majority of studies, the interfacial structure is assumed to arise from a relatively static lowest energy configuration of atoms, even at room temperature. Using hematite (α-FeO) as a model oxide, we show through a direct comparison of in situ synchrotron X-ray scattering with density functional theory-based molecular dynamics simulations that the structure of the (11̅02) termination is dynamically stabilized by picosecond water exchange.

High Pressure Single Crystal Diffraction at PX^2.

In this report we describe detailed procedures for carrying out single crystal X-ray diffraction experiments with a diamond anvil cell (DAC) at the GSECARS 13-BM-C beamline at the Advanced Photon Source. The DAC program at 13-BM-C is part of the Partnership for Extreme Xtallography (PX^2) project. BX-90 type DACs with conical-type diamond anvils and backing plates are recommended for these experiments.

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.

UO(2) Oxidative Corrosion by Nonclassical Diffusion.

Using x-ray scattering, spectroscopy, and density-functional theory, we determine the structure of the oxidation front when a UO(2) (111) surface is exposed to oxygen at ambient conditions. In contrast to classical diffusion and previously reported bulk UO(2+x) structures, we find oxygen interstitials order into a nanoscale superlattice with three-layer periodicity and uranium in three oxidation states: IV, V, and VI. This oscillatory diffusion profile is driven by the nature of the electron transfer process, and has implications for understanding the initial stages of oxidative corrosion in materials at the atomistic level.

Surface-mediated formation of Pu(IV) nanoparticles at the muscovite-electrolyte interface.

The formation of Pu(IV)-oxo-nanoparticles from Pu(III) solutions by a surface-enhanced redox/polymerization reaction at the muscovite (001) basal plane is reported, with a continuous increase in plutonium coverage observed in situ over several hours. The sorbed Pu extends >70 Å from the surface with a maximum concentration at 10.5 Å and a total coverage of >9 Pu atoms per unit cell area of muscovite (0.

Quantitative separation of monomeric U(IV) from UO2 in products of U(VI) reduction.

The reduction of soluble hexavalent uranium to tetravalent uranium can be catalyzed by bacteria and minerals. The end-product of this reduction is often the mineral uraninite, which was long assumed to be the only product of U(VI) reduction. However, recent studies report the formation of other species including an adsorbed U(IV) species, operationally referred to as monomeric U(IV).

Oxidative Dissolution of Biogenic Uraninite in Groundwater at Old Rifle, CO.

Reductive bioremediation is currently being explored as a possible strategy for uranium-contaminated aquifers such as the Old Rifle site (Colorado). The stability of U(IV) phases under oxidizing conditions is key to the performance of this procedure. An in situ method was developed to study oxidative dissolution of biogenic uraninite (UO₂), a desirable U(VI) bioreduction product, in the Old Rifle, CO, aquifer under different variable oxygen conditions.

Electron microbeam investigation of uranium-contaminated soils from Oak Ridge, TN, USA.

Two samples of uranium-contaminated soil from the Department of Energy's Oak Ridge Reservation in Oak Ridge, Tennessee were investigated using electron microprobe analysis and transmission electron microscopy. The objectives of this research were to identify and characterize soil particles and rock chips with high uranium concentrations, to investigate the extent of uranium penetration into chips of parent material, and to identify solid-phase hosts for uranium in the samples. Three distinct solid-phase hosts for uranium have been identified: (1) iron oxyhydroxides, including goethite and ferrihydrite; (2) mixed Mn-Fe oxides; and (3) discrete uranium phosphates.