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Isomer-Tailored Carbon Molecular Sieve Membranes with High Gas Separation Performance
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An Automated Ultraclean Ion Exchange Separation Method for the Determinations of 232Th and 238U in Copper using Inductively Coupled Plasma Mass Spectrometry
This work presents a novel automated analytical method developed for high throughput ultrasensitive determinations of Th and U in copper using inductively coupled plasma mass spectrometry (ICP-MS). The method is based on the use of ultra clean sample preparation procedures including the use of a fully automated off-line chromatography system for the extraction and pre-concentration of the analytes prior to ICP-MS analysis. The separation system is equipped with a single reusable chromatographic column that, with the rigorously clean procedures developed herein, provided a low carryover, low background, and reproducible automated separation method. Isotope dilution methods were used for quantitation. Method Detection Limits (MDLs) of 3.7 and 9.4 fg·g-1 were obtained for the quantitation of 232Th and 238U in copper, respectively, corresponding to activities of 0.0148 and 0.116 microBq·kg-1 for 232Th and 238U, respectively. The analytical method provided high and reproducible tracer recoveries. The use of an automated system significantly reduced the extremely tedious active work time required for the chemist (by ca. 80%) relative to manually performing the separation. This method could be adapted to other critical sample matrices requiring the utmost in high throughput clean chemistry procedures for automated ultrasensitive analyses.
Examining the Influence of Silver(I) Ion Coordination Environment in Ionic Liquids on Olefin–Paraffin Separations using Inverse Gas Chromatography
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What Are the Best Materials To Separate a Xenon/Krypton Mixture?
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Excited-State Studies of Polyacenes: A Comparative Picture Using EOMCCSD, CR-EOMCCSD(T), Range-Separated (LR/RT)-TDDFT, TD-PM3, and TD-ZINDO
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Hierarchically Porous Polymer Monoliths by Combining Controlled Macro- and Microphase Separation
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Separation of Xylene Isomers through Multiple Metal Site Interactions in Metal–Organic Frameworks
Purification of the C 8 alkylaromatics o-xylene, m-xylene, p-xylene, and ethylbenzene remains among the most challenging industrial separations, due to the similar shapes, boiling points, and polarities of these molecules. We report the evaluation of the metal-organic frameworks Co 2 (dobdc) (dobdc 4- = 2,5-dioxido-1,4-benzenedicarboxylate) and Co 2 ( m-dobdc) ( m-dobdc 4- = 4,6-dioxido-1,3-benzenedicarboxylate) for the separation of xylene isomers using single-component adsorption isotherms and multicomponent breakthrough measurements. Remarkably, Co 2 (dobdc) distinguishes among all four molecules, with binding affinities that follow the trend o-xylene > ethylbenzene > m-xylene > p-xylene. Multicomponent liquid-phase adsorption measurements further demonstrate that Co 2 (dobdc) maintains this selectivity over a wide range of concentrations. Structural characterization by single-crystal X-ray diffraction reveals that both frameworks facilitate the separation through the extent of interaction between each C 8 guest molecule with two adjacent cobalt(II) centers, as well as the ability of each isomer to pack within the framework pores. Moreover, counter to the presumed rigidity of the M 2 (dobdc) structure, Co 2 (dobdc) exhibits an unexpected structural distortion in the presence of either o-xylene or ethylbenzene that enables the accommodation of additional guest molecules.
cis,cis-Muconic acid: separation and catalysis to bio-adipic acid for nylon-6,6 polymerization
cis , cis -Muconic acid for downstream separation and catalytic upgrading to adipic acid for nylon-6,6 polymerization.
Unblocking a rigid purine MOF for kinetic separation of xylenes
The separation of xylene isomers still remains an industrially challenging task. Here, we synthesized and studied porous purine-based metal–organic frameworks (MOFs) for their potential in xylene separations. In particular, Zn(purine)I showed excellent para-xylene/ortho-xylene separation capability with a diffusion selectivity of 6 and high equilibrium adsorption selectivity as indicated by coadsorption experiments. This high selectivity is attributed to the shape and size of the channel aperture within the rigid framework of Zn(purine)I.
Charge separation at nanoscale interfaces: Energy-level alignment including two-quasiparticle interactions
The universal and fundamental criteria for charge separation at interfaces involving nanoscale materials are investigated. In addition to the single-quasiparticle excitation, all the two-quasiparticle effects including exciton binding, Coulomb stabilization, and exciton transfer are considered, which play critical roles on nanoscale interfaces for optoelectronic applications. We propose a scheme allowing adding these two-quasiparticle interactions on top of the single-quasiparticle energy level alignment for determining and illuminating charge separation at nanoscale interfaces. Employing the many-body perturbation theory based on Green's functions, we quantitatively demonstrate that neglecting or simplifying these crucial two-quasiparticle interactions using less accurate methods is likely to predict qualitatively incorrect charge separation behaviors at nanoscale interfaces where quantum confinement dominates.
Highly concentrated nebular noble gases in porous nanocarbon separates from the Saratov (L4) meteorite
The majority of heavy noble gases (Ar, Kr, and Xe) in primitive meteorites are stored in a poorly understood phase called Q. Although Q is thought to be carbonaceous, the full identity of the phase has remained elusive for almost four decades. In order to better characterize phase Q and, in turn, the early solar nebula, we separated carbon-rich fractions from the Saratov (L4) meteorite. We chose this meteorite because Q is most resistant in thermal alteration among carbonaceous noble gas carriers in meteorites and we hoped that, in this highly metamorphosed meteorite, Q would be present but not diamond: these two phases are very difficult to separate from each other. One of the fractions, AJ, has the highest {sup 132}Xe concentration of 2.1 × 10{sup –6} cm{sup 3} STP g{sup –1}, exceeding any Q-rich fractions that have yet been analyzed. Transmission electron microscopy studies of the fraction AJ and a less Q-rich fraction AI indicate that they both are primarily porous carbon that consists of domains with short-range graphene orders, with variable packing in three dimensions, but no long-range graphitic order. The relative abundance of Xe and C atoms (6:10{sup 9}) in the separates indicates that individual noble gas atoms are associated with only a minor component of the porous carbon, possibly one or more specific arrangements of the nanoparticulate graphene.
Separable and non-separable multi-field inflation and large non-Gaussianity
In this paper we provide a general framework based on δN formalism to estimate the cosmological observables pertaining to the cosmic microwave background radiation for non-separable potentials, and for generic end of inflation boundary conditions. We provide analytical and numerical solutions to the relevant observables by decomposing the cosmological perturbations along the curvature and the isocurvature directions, instead of adiabatic and entropy directions. We then study under what conditions large bi-spectrum and tri-spectrum can be generated through phase transition which ends inflation. In an illustrative example, we show that large f{sub NL} ∼ O(80) and τ{sub NL} ∼ O(20000) can be obtained for the case of separable and non-separable inflationary potentials.
2013 Actinide Separation Conference Presentations on Minor Actinide Separations by SRNL Participants [Slides]
Attached are copies of the presentations that will be given by Savannah River National Laboratory participants at the 37th Actinide Separations Conference in Spokane, Washington on June 24 – 27, 2013. This document represents the deliverable for milestone M4FT-13SR0303062, Prepare and present two papers on ion exchange separations at the 2013 Actinide Separations conference. Note that the completion of the milestone was delayed due to the rescheduling of the conference from late May 2013 to late June 2013.
Ferrofluid separator for nonferrous scrap separation
Behavior of nonmagnetic objects within separator is essentially function of density, and independent of size or shape of objects. Results show close agreement between density of object and apparent density of ferrofluid required to float it. Results also demonstrate that very high separation rates are achievable by ferrofluid sink-float separation.