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  1. The Remarkable I2O3 Molecule: A New View from Theory

    Tang, Carson L. ; Turney, Justin M. ; Schaefer, Henry F. - The Journal of Physical Chemistry A
    Atmospheric iodine chemistry has garnered increasing attention as a result of increased iodine emissions. A key subset of this chemistry involves iodine oxides (I2O2–5), which serve as precursors to particle formation. Among these, I2O3 is the simplest iodine oxide involved in particle formation, but it has remained undetected in the atmosphere. Previous theoretical studies have characterized this peculiar molecule, primarily using energies to refine geometries obtained at low levels of theory. Due to the reemerging interest in I2O3, this study presents geometries optimized at the CCSD(T)/aug-cc-pwCVTZ-PP level of theory─marking the first instance, to the best of our knowledge, where thismore » system has been studied exclusively with CCSD(T). Harmonic vibrational frequencies were computed at the same level of theory. Final energetics were obtained using the very high level CCSDT(Q) method with basis sets up to quintuple-zeta cardinality (aug-cc-pwCV5Z-PP) and extrapolated to the CBS limit to yield CCSDT(Q)/CBS//CCSD(T)/aug-cc-pwCVTZ-PP energies. These energies include harmonic zero-point vibrational energy corrections and scalar relativistic energy corrections. Additionally, this study discovers new isomers along the I2O3 potential energy surface, a novel contribution to the field. The performance of different computational methods and DFT functionals commonly used in atmospheric chemistry is also assessed relative to high-level theoretical methods.« less

  2. Pelletization with Spark Plasma Sintering and Characterization of Metal Iodides: An Assessment of Long-Term Radioiodine Immobilization Options

    Oshiro, Jared M. ; Fujii Yamagata, Alessandra Lie ; Sharma, Saurabh Kumar ; ... - Industrial and Engineering Chemistry Research
    Four promising iodine “getter” materials (Ag, Cu, Bi, and Sn) for radioiodine capture were assessed in their pure metal-iodide (MIx) pelletized forms to compare relative chemical durabilities. To study chemical durability, commercial MIx compounds of AgI, BiI3, BiOI, CuI, and SnI4 were converted to dense monolithic pellets using spark plasma sintering. Semidynamic leach testing in the form of modified ASTM C1308 tests was then performed on the pellets in two different forms including unmounted (as-pressed) specimens (i.e., “U”) and epoxy-mounted specimens (i.e., “M”) with polished surfaces. The chemical durability results and sample characterizations showed that three of the five MIxmore » compounds tested (i.e., AgI, CuI, and BiOI) displayed moderate to high leach resistances. Further, the remaining two MIx compounds (i.e., BiI3 and SnI4), which are both desirable iodine waste forms due to their high iodine loading capacities, readily decomposed during leach testing, indicated by crystallographic changes in the specimens as well as large amounts of iodine detected in the leachate solutions. The instabilities of BiI3 and SnI4 raise uncertainties for using the base metals/cations (i.e., Bi0/Bi3+ and Sn0/Sn4+, respectively) as viable getters for radioiodine capture due to likely poor waste form chemical durabilities after capture and consolidation into waste forms.« less

  3. Ocean acidification significantly alters the trace element content of the kelp, Saccharina latissima

    Schultz, Jack ; Berry Gobler, Dianna L. ; Young, Craig S. ; ... - Marine Pollution Bulletin

  4. Iodine Modulates the MACl‐Assisted Growth of FAPbI3 for High Efficiency Perovskite Solar Cells (in EN)

    Hu, Junnan ; Ahn, Jae Won ; Xu, Zhaojian ; ... - Advanced Energy Materials
    The preferential growth of α-phase formamidinium perovskite (α-FAPbI3) at low temperatures can be achieved with the incorporation of chloride-based additives, with methylammonium chloride (MACl) being the most common example. However, compared to other less-volatile chloride additives, MACl only remains in the growing perovskite film for a short time before evaporating during annealing, primarily influencing the early stages of film formation. In addition, evaporation of MACl as methylamine (MA0) and HCl can introduce a side reaction between MA0 and formamidinium (FA), undermining the compositional purity and phase stability of α-FAPbI3. In this study, it is demonstrated that addition of iodine (I2)more » into the FAPbI3 precursor solution containing MACl suppresses the MA-FA side reaction during annealing. Additionally, MACl evaporation is delayed owing to strong interaction with triiodide. The added I2 facilitates spontaneous growth of α-FAPbI3 prior to annealing, with an improved bottom morphology due to the formation of fewer byproducts. Perovskite solar cells derived from an I2-incorporated solution deliver a champion power conversion efficiency of 25.2% that is attributed to suppressed non-radiative recombination.« less

  5. Boron and lithium aqueous thermochemistry to model crud deposition in pressurized water reactors

    Rizk, Jason Tyler ; McMurray, Jacob W. ; Wirth, Brian D. - Journal of Chemical Thermodynamics
    Here, a comprehensive database of boron and lithium aqueous thermochemistry has been developed for use at elevated temperatures. The Helgeson-Kirkham-Flowers (HKF) formalism provides a framework to describe thermodynamic properties over a broad range of temperatures and pressures. Accuracy at high temperatures is vital to modeling nickel oxide and ferrite fuel deposits that occur in pressurized water nuclear reactors (PWRs). CALPHAD (CALculation of PHAse Diagrams) calculations are performed at PWR crud conditions to predict the stability regions of the solid lithium metaborate (LiBO2) and lithium tetraborate (Li2B4O7) precipitates. In addition, similar calculations are performed using sodium and potassium instead of lithiummore » in order to assess the thermodynamics associated with preventing the formation of such precipitates. This database contributes to understanding of crud formation and composition and will aid in the prediction of phenomena such as Crud-Induced Power Shifts (CIPS).« less

  6. Experimental and Numerical Study of Radioiodine Sorption and Transport in Hanford Sediments

    He, Xiaoliang ; Rockhold, Mark L. ; Fang, Yilin ; ... - ACS Earth and Space Chemistry

  7. I–/I3– Redox-Assisted Synthesis and Properties of Low Dimensional, Mixed-Valent Gold Iodide Perovskite Derivatives

    Walusiak, Benjamin W. ; Raghavan, Adharsh ; Cahill, Christopher L. - Crystal Growth and Design
    Here, we report a set of three new mixed-valent AuI AuIII iodides: (ClPy)3[AuI2]2[AuI4] [1], (BrPy)3[AuI2]2[AuI4] [2], and (ClPy)2[AuI2][AuI4] [3], as well as three new monovalent AuIII iodides: (XPy)2[AuI4][I3] (Py = 4-X-pyridinium X = Cl, Br, and I) [4–6]. Two of these mixed-valent compounds (1 and 2) incorporate both monovalent AuI···AuI (aurophilic bonding) and mixed-valent AuII···AuIIII couples (Au–I halogen bonding), to the best of our knowledge an unprecedented structural feature. These same two mixed-valent compounds also exhibit a rare low-dimensional molecular architecture with respect to second sphere Au···I interactions, namely, 1D chains of Au···I interactions, extending along a single crystallographic axis.more » All compounds were synthesized with the assistance of the I–/I3– redox couple and tacit manipulation of the polyiodide content during synthesis. Air-free synthesis was used to influence the redox process of I–/I3–, resulting in better selection for mixed-valent products. Compounds 1–2 and 4–5 exhibit a characteristically narrow bandgap (1.04–1.25 eV), as measured via diffuse reflectance spectroscopy (DRS). Computational analyses were used to rationalize the specific assembly modes of [AuI2]– and [AuI4]– species, and they show that the AuI···I interaction type is favored over the AuIII···I.« less

  8. Removal of fission product tellurium and iodine from recently irradiated HEU using copper metal

    Uhnak, Nicolas E. ; Saslow, Sarah A. ; Bowen, James M. ; ... - Journal of Radioanalytical and Nuclear Chemistry
    Gamma detection of select fission products or activation products such as 153Sm and 239Np in a fission sample is difficult due to gamma interferences from radiotellurium and radioiodine. To aid in the detection of these difficult-to-detect nuclides, the radiotellurium and radioiodine were removed using Cu metal turnings. This method is highly effective at the removal of the interfering radionuclides removing > 98% of the radiotellurium and radioiodine. A mechanistic study was conducted. Determining the deposition mechanism, using a number of techniques including XANES and electrochemistry providing an understanding of the electrochemical path for the Te deposition. Initial work focused onmore » the use of stable Te, further expanding into activated TeO2, and a fresh fission sample. Importantly, this method presents a rapid method for the direct detection of select fission products that could have a significant impact on nuclear related fields including nuclear forensics.« less

  9. Enhanced Iodine Capture Using a Postsynthetically Modified Thione–Silver Zeolitic Imidazole Framework

    Kim, Min-Bum ; Yu, Jierui ; Ra Shin, Sun Hae ; ... - ACS Applied Materials and Interfaces
    Efficient management of radionuclides that are released from various processes in the nuclear fuel cycle is of significant importance. Among these nuclides, radioactive iodine (mainly 129I and 131I) is a major concern due to the risk it poses to the environment and to human health; thus, the development of materials that can capture and safely store radioactive iodine is crucial. Herein, a novel silver-thione-functionalized zeolitic imidazole framework (ZIF) was synthesized via post-synthetic modification and assessed for its iodine uptake capabilities alongside the parent ZIF-8 and intermediate materials. A solvent-assisted ligand exchange procedure was used to replace the 2-methylimidazole linkers inmore » ZIF-8 with 2-mercaptoimidazole, forming the intermediate compound ZIF-8=S, which was reacted with AgNO3 to yield the ZIF-8=S-Ag+ composite for iodine uptake. Despite possessing the lowest BET surface area of the derivatives, the Ag-functionalized material demonstrated superior I2 adsorption in terms of both maximum capacity (550 g I2/mol) and rapid kinetics (50% loading achieved in 5 hrs, saturation in 50 hrs) compared to our pristine ZIF-8, which reached 450 g I2/mol after 150 hours and 50% loading in 25 hours. This improvement is attributed to the presence of the Ag+ ions, which provide a strong chemical driving force to form stable Ag-I species. In conclusion, the results of this study contribute to a broader understanding of the strategies that can be employed to engineer adsorbents with robust iodine uptake behavior.« less

  10. Accumulation mechanisms for contaminants on weak-base hybrid ion exchange resins

    Saslow, Sarah A. ; Cordova, Elsa A. ; Escobedo Avalos, Nancy M. ; ... - Journal of Hazardous Materials
    Mechanism of hexavalent chromium removal (Cr(VI) as CrO42-) by the weak-base ion exchange (IX) resin ResinTech® SIR-700-HP (SIR-700) from simulated groundwater is assessed in the presence of radioactive contaminants iodine-129 (as IO3-), uranium (U as uranyl UO22+), and technetium-99 (as TcO4-), and common environmental anions sulfate (SO42-) and chloride (Cl-). Batch tests using the acid sulfate form of SIR-700 demonstrated Cr(VI) and U(VI) removal exceeded 97%, except in the presence of high SO42- concentrations (536 mg/L) where Cr(VI) and U(VI) removal decreased to ≥ 80%. However, Cr(VI) removal notably improved with co-mingled U(VI) that complexes with SO42- at the protonatedmore » amine sites. These U–SO42- complexes are integral to U(VI) removal, as confirmed by the decrease in U(VI) removal (<40%) when the acid chloride form of SIR-700 was used instead. Solid phase characterization revealed that CrO42- is removed by IX with SO42- complexes and/or reduced to amorphous Cr(III)(OH)3 at secondary alcohol sites. Tc(VII)O4- and I(V)O3- also undergo chemical reduction, following a similar removal mechanism. Oxyanion removal preference is determined by the anion reduction potential (CrO42->TcO4->IO3-), geometry, and charge density. For these reasons, 39% and 69% of TcO4- and 17% and 39% of IO3- are removed in the presence and absence of Cr(VI), respectively.« less
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