EMSL: Bruce Arey's Publications

Krupka KM, MA Parkhurst, K Gold, BW Arey, ED Jenson, and RA Guilmette. 2009. "Physicochemical Characterization of Capstone Depleted Uranium Aerosols III: Morphologic and Chemical Oxide Analyses." Health Physics 93(3):276-291. doi:10.1097/01.HP.0000298229.60229.10 Abstract The impact of depleted uranium (DU) penetrators against an armored target causes erosion and fragmentation of the penetrators, the extent of which is dependent on the thickness and material composition of the target. Vigorous oxidation of the DU particles and fragments creates an aerosol of DU oxide particles and DU particle agglomerations combined with target materials. Aerosols from the Capstone DU aerosol study, in which vehicles were perforated by DU penetrators, were evaluated for their oxidation states using X-ray diffraction (XRD) and particle morphologies using scanning electron microscopy/energy dispersive spectrometry (SEM/EDS). The oxidation state of a DU aerosol is important as it offers a clue to its solubility in lung fluids. The XRD analysis showed that the aerosols evaluated were a combination primarily of U3O8 (insoluble) and UO3 (relatively more soluble) phases, though intermediate phases resembling U4O9 and other oxides were prominent in some samples. Analysis of particle residues in the micrometer-size range by SEM/EDS provided microstructural information such as phase composition and distribution, fracture morphology, size distribution, and material homogeneity. Observations from SEM analysis show a wide variability in the shapes of the DU particles. Some of the larger particles appear to have been fractured (perhaps as a result of abrasion and comminution); others were spherical, occasionally with dendritic or lobed surface structures. Amorphous conglomerates containing metals other than uranium were also common, especially with the smallest particle sizes. A few samples seemed to contain small chunks of nearly pure uranium metal, which were verified by EDS to have a higher uranium content exceeding that expected for uranium oxides. Results of the XRD and SEM/EDS analyses were used in other studies described in this issue of The Journal of Health Physics to interpret the results of lung solubility studies and in selecting input parameters for dose assessments.

Neiner D, AJ Karkamkar, JC Linehan, BW Arey, T Autrey, and SM Kauzlarich. 2009. "Promotion of Hydrogen Release from Ammonia Borane with Mechanically Activated Hexagonal Boron Nitride." Journal of Physical Chemistry C 113(3):1098-1103. doi:10.1021/jp8087385 Abstract We present the activation of hydrogen release from AB by the presence of mechanically activated h–BN. Hydrogen is released at lower temperatures and the dehydrogenation is less exothermic than neat AB. This approach provides all the benefits of a light-weight scaffold without additional foreign contamination that might complicate AB recycling. Several beneficial effects that pertain to the hydrogen desorption properties of the mixtures of AB:nano-BN are notable, such as the decrease of hydrogen desorption temperature, the decrease in NH3 formation as well as the decrease of the exothermicity of hydrogen desorption with increasing the nano-BN concentration. The lower exothermicity of H2 release from AB in the mesoporous silica and the nano-BN may be due physical and chemical interactions between the PAB oligomers and the interface of the silica scaffold or BN support. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

Peretyazhko T, JM Zachara, JF Boily, Y Xia, PL Gassman, BW Arey, and WD Burgos. 2009. "Mineralogical transformations controlling acid mine drainage chemistry." Chemical Geology 262(3-4):169-178. Abstract The role of Fe(III) minerals in controlling acid mine drainage (AMD) chemistry was studied using samples from two AMD sites [Gum Boot (GB) and Fridays-2 (FR)] located in northern Pennsylvania. Chemical extractions, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were used to identify and characterize Fe(III) phases. The mineralogical analysis revealed that schwertmannite and goethite were the principal Fe(III) phases in the sediments. Schwertmannite transformation occurred at the GB site where poorly-crystallized goethite rich in surface-bound sulfate was initially formed. In contrast, no schwertmannite transformation occurred at the FR site. The goethite in GB sediments had spherical morphology due to preservation of schwertmannite structure by adsorbed sulfate. Results of chemical extractions showed that poorly-crystallized goethite was subject to further crystallization accompanied by sulfate desorption. Changes in sulfate speciation preceded its desorption, with a conversion of bidentate- to monodentate-bound sulfate surface complexes. Laboratory sediment incubation experiments were conducted to evaluate the effect of mineral transformation on water chemistry. Incubation experiments were carried out with schwertmannite-containing sediments and AMD waters with different pH and chemical composition. The pH decreased to 1.9-2.2 in all suspensions and the concentrations of dissolved Fe and S increased significantly. Regardless of differences in the initial water composition, pH, Fe and S were similar in suspensions of the same sediment. XRD measurements revealed that schwertmannite transformed into goethite in GB and FR sediments during laboratory incubation. The incubation experiment demonstrated that schwertmannite transformation controlled AMD water chemistry during “closed system” laboratory contact.

Qafoku N, L Zhong, CJ Thompson, C Liu, BW Arey, AV Mitroshkov, and RG Riley. 2009. "Physical control on CCl4 and CHCl3 desorption from artificially contaminated and aged sediments with supercritical carbon dioxide ." Chemosphere 74(4):494-500. Abstract The long-term interactions of carbon tetrachloride (CCl4) and chloroform (CHCl3) with sediments that are low in organic matter (OM) are not well studied and documented in the literature. In this study, CCl4 and CHCl3 were mixed with supercritical carbon dioxide (CO2) and loaded onto columns packed with two sediments with low OM content and different textures, to establish contamination and achieve expedited artificial aging. The columns were subsequently leached with a simulated groundwater under hydraulically saturated conditions. Scanning electron microscopy was used to inspect the morphology of sediment single particles, determine the degree of particle association in aggregates and qualitatively estimate porosity and the length of possible diffusional pathways that might affect the overall contaminant desorption rates in sediments with low sorption capacity. Results demonstrated that most of contaminant inventories were rapidly released in the first pore volume of effluent, although a small portion of contaminants’ total mass exhibited time-dependent desorption. The calculated Kd values of CCl4 or CHCl3 partition were negligibly small. The transport behavior of both contaminants was similar and it was simulated well with a distributed (multiple)-rate (DR) statistical model, which accounted for the apparent contaminant mass transfer through diffusional pathways of different lengths, towards the advective pores. The distribution of contaminant mass between equilibrium and kinetic fractions, the distribution of the individual rate constants, and the average rate constants calculated with the parameters of the γ-distribution function (β and η) of the DR model, were sediments (texture) dependent, indicating that contaminant desorption during the late stage of leaching was driven by concentration gradients (i.e., diffusion) within sediment matrix porosity.

Smith SC, M Douglas, DA Moore, RK Kukkadapu, and BW Arey. 2009. "Uranium Extraction From Laboratory Synthesized, Uranium-Doped Hydrous Ferric Oxides ." Environmental Science & Technology 43:2341-2347. Abstract The extractability of uranium (U) from synthetic hydrous ferric oxides has been shown to decrease as a function of mineral ripening, consistent with the hypothesis that the ripening process decrease contaminant lability. To evaluate this process, three hydrous ferric oxide (HFO) suspensions were co-precipitated with uranyl (UO22+) and maintained at pH 7.0 ± 0.1. Uranyl was added to the HFO post-precipitation in a fourth suspension. Two suspensions also contained either co-precipitated silicate (Si-U-HFO) or phosphate (P-U-HFO). After precipitation of the HFOs, at time intervals of one week, one month, six months, one year, and 2 years, aliquots of the suspensions were contacted with five solutions for a range of time. The extracts were analyzed for U and iron (Fe). The results are consistent with the hypothesis that U and Fe extractability will decrease as the mineral phase ripens. All extracting solutions exhibited some degree of selectivity for U, as the proportional extraction of U exceeded that for congruent dissolution. Micro X-ray diffraction analysis indicates the transformation from an amorphous phase to a material containing substantial proportions of crystalline goethite and hematite, except the P-U-HFO which remained primarily amorphous. Further analysis of the co-precipitates by the Mössbauer technique and scanning electron microscopy (SEM) provides further evidence of mineralogic ripening

Shin Y, IT Bae, BW Arey, and GJ Exarhos. 2008. "Facile stabilization of gold-silver alloy nanoparticles on cellulose nanocrystal." Journal of Physical Chemistry C 112(13):4844-4848. doi:10.1021/jp710767w Abstract Uniform Au-Ag alloy nanoparticles have been synthesized on cellulose nanocrystal (CNXL) by co-reduction method of corresponding metal ions. CNXL that plays a dual role of a matrix and of a stabilizer has been used to obtain stable dispersions of alloy nanoparticles. The composition of alloy nanoparticles indicates quantitative deposit of metal ions on CNXL surface followed by reduction. The sizes of alloy nanoparticles were controlled in the range of 3-7 nm by capping agent, sodium citrate, and their average diameter was increased with an increase of Ag content. Aqueous suspensions of Au-Ag alloy nanoparticles and their dried films are characterized by UV-Vis spectroscopy, Field Emission-Scanning Electron Microscope (FE-SEM), Transmission Electron Microscope (TEM), and X-ray Diffraction (XRD).

Shin Y, LQ Wang, IT Bae, BW Arey, and GJ Exarhos. 2008. "Hydrothermal Syntheses of Colloidal Carbon Spheres from Cyclodextrins." Journal of Physical Chemistry C 112(37):14236-14240. doi:10.1021/jp801343y Abstract Colloidal carbon spheres have been prepared from aqueous alpha-, beta-, and gamma-cyclodextrin (CD) solutions in closed systems under hydrothermal conditions at 160 oC. Both liquid and solid-state 13C NMR spectra taken for samples at different reaction times have been used to monitor the dehydration and carbonization pathways. CD slowly hydrolyzes to glucose and forms 5-hydroxymethyl furfural (HMF) followed by carbonization into colloidal carbon spheres. The isolated carbon spheres are 70-150 nm in diameter, exhibit a core-shell structure, and are comprised of a condensed core (C=C) peppered with resident chemical functionalities including carboxylate and hydroxyl groups. Evidence from 13C solid-state NMR and FT-IR spectra reveal that the evolving carbon spheres show a gradual increase in the amount of aromatic carbon as a function of reaction time and that the carbon spheres generated from gamma-CD contain significantly higher aromatic carbon than those derived from alpha- and beta-CD.

Flaherty DW, Z Dohnalek, A Dohnalkova, BW Arey, DE McCready, N Ponnusany, CB Mullins, and BD Kay. 2007. "Reactive Ballistic Deposition of Porous TiO2 Films: Growth and Characterization." Journal of Physical Chemistry C 111(12):4765-4773. doi:10.1021/jp067641m Abstract Nanoporous, high-surface area films of TiO2 are synthesized by reactive ballistic deposition of titanium metal in an oxygen ambient. Auger electron spectroscopy (AES) is used to investigate the stoichiometric dependence of the films on growth conditions (surface temperature and partial pressure of oxygen). Scanning and transmission electron microscopy show that the films consist of arrays of separated filaments. The surface area and the distribution of binding site energies of the films are measured as functions of growth temperature, deposition angle, and annealing conditions using temperature programmed desorption (TPD) of N2. TiO2 films deposited at 50 K at 70º from substrate normal display the greatest specific surface area of ~100 m2/g. In addition, the films retain greater than 70% of their original surface area after annealing to 600 K. The combination of high surface area and thermal stability suggest that these films could serve as supports for applications in heterogeneous catalysis.

Pierce EM, BP McGrail, PPNNL Martin, JC Marra, BW Arey, and KN Geiszler. 2007. "Accelerated Weathering of High-Level and Plutonium-bearing Lanthanide Borosilicate Waste Glasses under Hydraulically Unsaturated Conditions." Applied Geochemistry 22(9):1841-1859. doi:10.1016/j.apgeochem.2007.03.056 Abstract A can-in-canister waste package design has been proposed for disposal of excess weapons plutonium at the proposed mined geologic repository at Yucca Mountain, NV. by the U. S. Department of Energy Office of Fissile Material Disposition. This configuration consists of a high-level waste (HLW) canister fitted with a rack that holds mini-canisters containing a Pu-bearing lanthanide borosilicate (LaBS) waste glass and/or ceramic (~15% of the total canister volume). The larger canister is then filled with HLW glass, SRL-202, (~85% of the total canister volume). A 6-year pressurized unsaturated flow (PUF) test was conducted to investigate waste form/waste form interactions that may occur when water penetrates the canisters and contacts the waste forms. Volumetric water content was observed to increase steadily during PUF testing from accumulation of water mass as waters of hydration associated with alteration phases formed on the glass surface. Periodic excursions in effluent pH, electrical conductivity, and solution chemistry were monitored and correlated with the formation of a clay phase(s) during the test. Thermodynamic modeling of select effluent solution samples suggests the dominant secondary reaction product for the SRL-202 glass is a smectite di-octahedral clay phase(s), possibly nontronite [Na0.33Fe2(AlSi)4O10(OH)2•n(H2O)] or beidellite [Na0.33Al2.33Si3.67O10(OH)2]. This phase was identified in SEM images as discrete spherical particles found growing out of a gel-layer on reacted SRL-202 glass. Plutonium analyses of filtered and unfiltered solutions indicate that >80% of the Pu exiting the PUF system is as filterable particulates. In this advection-dominated system, Pu is migrating principally as colloids after being released from the LaBS glass. Analysis of reacted LaBS glass using SEM-EDS illustrates that Pu has segregated into a discrete disk-like phase, possibly PuO2. Alteration products that contain the neutron absorber Gd have not been positively identified. Separation of the Pu and its neutron absorbers during glass dissolution and transport is a potential criticality concern in the proposed repository. However, the translation and interpretation of these long-term PUF test results to actual disposed waste packages requires further analysis.

Shin Y, IT Bae, BW Arey, and GJ Exarhos. 2007. "Simple Preparation and Stabilization of Nickel Nanocrystals on Cellulose Nanocrystal." Materials Letters 64(14-15):3215-3217. doi:10.1016/j.matlet.2006.11.036 Abstract Nickel nanocrystals were simply prepared on the carbon through a thermal reduction process at 400-500oC under N2 after Ni(II) ions were deposited and stabilized on cellulose nanocrystal (CNXL) surface. Hydroxyl groups on the CNXL anchor and stabilize Ni(II) ions. Well-dispersed Ni nanocrystals on the carbonized CNXL were about 5-12 nm in size. XRD, FESEM, and TEM were employed to characterize the products.