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Duer Bolotaulo, Alejandro Metta-Magaña, Skye Fortier
Using an improved, chromatography-free dipyrrin synthesis, the α,β-unsubstituted dipyrrins [RC(C4H2N)2H] (2) (R = tolyl (2toly(l)), p-OMe-C6H4 (2anis), mesityl (2mes), ferrocenyl (2Fc)) were isolated in good to excellent yields. Deprotonation of 2 with Na[N(SiMe3)2] gives the alkali metal salts [Na(DME)n][RC(C4H2N)2] (3) which reacts with UO2Cl2(THF)3 to give the uranyl bis(dipyrrinates) UO2[RC(C4H2N)2]2(L) (L = THF (4R-THF); DMAP (4R-DMAP)) (R = tolyl, p-OMe-C6H4, mesityl, ferrocenyl). The THF adducts, 4R-THF, are unstable in aromatic and nonpolar solvents and rapidly decompose to 2 and an intractable uranium-containing solid...
February 22, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Ke Tong
The aim of this study was to assess the effect of alginate-chitosan microcapsule on viability characteristics of Bacillus subtilis and the ability of B. subtilis/alginate-chitosan microcapsule to remove uranium ion from aqueous solution. The effects of particle size, chitosan molecular weight and inoculum density on viability characteristics were studied using alginate-chitosan microcapsule-immobilized B. subtilis experiments. In addition, the effects of pH, immobilized spherule dosage, temperature, initial uranium ion concentration and contact time on removal of uranium ion were studied using batch adsorption experiments...
2017: Nanotechnology, Science and Applications
Yanli Li, Jinghan Zou, Xiao-Gen Xiong, Jing Su, Hua Xie, Zejie Fei, Zichao Tang, Hong-Tao Liu
Since the renewal of the research on thorium based molten salt reactor, there is growing demand and interest in enhancing the knowledge of thorium chemistry both experimentally and theoretically. Compared with uranium, few chemical studies of thorium have been reported up to the present. Here we report the vibrational resolved photoelectron imaging of thorium monoxide anion. The electron affinity of ThO is firstly reported to be 0.707 ± 0.020 eV. Vibrational frequencies of ThO molecule and its anion are determined from Franck-Condon simulation...
February 21, 2017: Journal of Physical Chemistry. A
Miha Trdin, Marijan Nečemer, Ljudmila Benedik
A new fast decomposition procedure for solid samples was developed. In this study, we investigated decomposition of samples by lithium borates fusion in combination with salicylic acid. The method described shortens the time required for the sample to be digested and loaded to a resin to up to 2 h, and it was especially suitable for alpha spectrometry measurements in emergency situations. Additionally, the method results in high radiochemical recoveries and when compared to other digestion methods (classical digestion utilizing mineral acids, microwave digestion, and lithium borates fusion in combination with polyethylene glycol (PEG)) gives comparable activity concentration values...
February 21, 2017: Analytical Chemistry
Anatoly Buchachenko, Ronald G Lawler
Chemistry is controlled by Coulomb energy; magnetic energy is lower by many orders of magnitude and may be confidently ignored in the energy balance of chemical reactions. The situation becomes less clear, however, when reaction rates are considered. In this case, magnetic perturbations of nearly degenerate energy surface crossings may produce observable, and sometimes even dramatic, effects on reactions rates, product yields, and spectroscopic transitions. A case in point that has been studied for nearly five decades is electron spin-selective chemistry via the intermediacy of radical pairs...
February 20, 2017: Accounts of Chemical Research
Steven B Yabusaki, Michael J Wilkins, Yilin Fang, Kenneth H Williams, Bhavna Arora, John R Bargar, Harry R Beller, Nicholas J Bouskill, Eoin L Brodie, John N Christensen, Mark E Conrad, Robert E Danczak, Eric King, Nicolas F Spycher, Carl I Steefel, Tetsu K Tokunaga, Roelof Jan Versteeg, Scott R Waichler, Haruko M Wainwright
Three-dimensional variably saturated flow and multicomponent biogeochemical reactive transport modeling, based on published and newly generated data, is used to better understand the interplay of hydrology, geochemistry, and biology controlling the cycling of carbon, nitrogen, oxygen, iron, sulfur, and uranium in a shallow floodplain. In this system, aerobic respiration generally maintains anoxic groundwater below an oxic vadose zone until seasonal snowmelt-driven water table peaking transports dissolved oxygen (DO) and nitrate from the vadose zone into the alluvial aquifer...
February 20, 2017: Environmental Science & Technology
Mumei Chen, Zheng Li, Jihao Li, Jingye Li, Qingnuan Li, Lan Zhang
A new approach for uranium extraction employing graphene aerogel (GA) as a skeleton loading organic solution (GA-LOS) is proposed and investigated. Firstly, the GA with super-hydrophobicity and high organic solution absorption capacity was fabricated by one-step reduction and self-assembly of graphene oxide with ethylenediamine. By adsorbing Tri-n-butyl phosphate (TBP)/n-dodecane solution to prepare GA-LOS, the extraction of U(VI) from nitric acid medium using GA-LOS was investigated and compared with conventional solvent extraction...
May 1, 2017: Talanta
Xin-Yan Zheng, Xiao-Yu Wang, Yang-Hao Shen, Xia Lu, Tie-Shan Wang
Biosorption of heavy metal elements including radionuclides by microorganisms is a promising and effective method for the remediation of the contaminated places. The responses of live Saccharomyces cerevisiae in the toxic uranium solutions during the biosorption process and the mechanism of uranium biomineralization by cells were investigated in the present study. A novel experimental phenomenon that uranium concentrations have negative correlation with pH values and positive correlation with phosphate concentrations in the supernatant was observed, indicating that hydrogen ions, phosphate ions and uranyl ions were involved in the chernikovite precipitation actively...
February 7, 2017: Chemosphere
Kimberly C Mullane, Patrick J Carroll, Eric J Schelter
Organic azides containing naphthyl functionalities were used to prepare uranium(V) imido complexes UV[=NC(2-naph)Ph2][N(SiMe3)2]3 (2), UV[=NC(2-naph)3][N(SiMe3)2]3 (3), and UV[=N(2-naph)][N(SiMe3)2]3 (4), and compared with UV[=NCPh3][N(SiMe3)2]3 (1). The electronic structures of these compounds were investigated by solution electrochemistry studies that revealed accessible U(V/VI), U(IV/V), and naphthalene0/naphthalene-1 couples. The uranium(V) naphthyl-imido complexes were reduced by potassium graphite to yield their uranium(IV) congeners K[UIV[=NC(2-naph)Ph2][N(SiMe3)2]3] (2-K), K[UIV[=NC(2-naph)3][N(SiMe3)2]3] (3-K), and K[UIV[=N(2-naph)][N(SiMe3)2]3] (4-K)...
February 16, 2017: Chemistry: a European Journal
Rohit Singh, Kishore Dutta, Malay K Nandy
A recent theoretical study [Phys. Rev. Lett. 112, 037202 (2014)10.1103/PhysRevLett.112.037202] has revealed that systems such as uranium ferromagnetic superconductors obey conserved dynamics. To capture the critical behavior near the paramagnetic to ferromagnetic phase transition of these compounds, we study the conserved critical dynamics of a nonlocal Ginzburg-Landau model. A dynamic renormalization-group calculation at one-loop order yields the critical indices in the leading order of ε=d_{c}-d, where d_{c}=4-2ρ is the upper critical dimension, with ρ an exponent in the nonlocal interaction...
January 2017: Physical Review. E
Nicolas P Martin, Juliane März, Christophe Volkringer, Natacha Henry, Christoph Hennig, Atsushi Ikeda-Ohno, Thierry Loiseau
Four metal-organic coordination polymers bearing uranium or neptunium have been hydrothermally synthesized from a tetravalent actinide chloride (AnCl4) and phthalic (1,2-H2bdc) or mellitic (H6mel) acid in aqueous media at 130 °C. With the phthalate ligand, two analogous assemblies ([AnO(H2O)(1,2-bdc)]2·H2O; An = U(4+) (1) or Np(4+) (2)) have been isolated, in which the square-antiprismatic polyhedra of AnO8 are linked to each other via μ3-oxo groups with an edge-sharing mode to materialize infinite zigzag ribbons...
February 16, 2017: Inorganic Chemistry
Karen R Burow, Kenneth Belitz, Neil M Dubrovsky, Bryant C Jurgens
Samples collected about one decade apart from 1105 wells from across the U.S. were compiled to assess whether uranium concentrations in the arid climate are linked to changing bicarbonate concentrations in the irrigated western U.S. Uranium concentrations in groundwater were high in the arid climate in the western U.S, where uranium sources are abundant. Sixty-four wells (6%) were above the U.S. EPA MCL of 30μg/L; all but one are in the arid west. Concentrations were low to non-detectable in the humid climate...
February 12, 2017: Science of the Total Environment
Lester Andrews, Han-Gook Cho, K Sahan Thanthiriwatte, David A Dixon
Thorium atoms from laser ablation react with phosphine during condensation in excess argon to produce two new infrared absorptions at 1467.2 and 1436.6 cm(-1) near weak bands for ThH and ThH2, which increase on annealing to 25 and 30 K, indicating spontaneous reactions. Analogous experiments with uranium produced two similar bands at 1473.4 and 1456.7 cm(-1) above UH at 1423.8 cm(-1) and another absorption at 1388.2 cm(-1). Electronic structure calculations at the coupled cluster CCSD(T) for Th and density functional theory calculations for U as well as their proximity to other actinide hydride absorptions support assignments of these bands to the simplest molecules HP═ThH2, HP═UH2, and PH2-UH...
February 14, 2017: Inorganic Chemistry
Isaac J Arnquist, Eric W Hoppe, Mary Bliss, Jay W Grate
A rapid new method for determining the U and Th mass concentrations in high radiopurity plastics is described, consisting of 1) dry ashing the plastic sample and tracers in low mass crucibles made of ultra low background electroformed copper (ULB EF-Cu) foil cut and folded into boats, 2) dissolving both the ash and the boat in acid, 3) performing a column separation to remove copper, and 4) determining the elements of interest by isotope dilution mass spectrometry. This method was demonstrated on both unfluorinated and fluorinated plastics, demonstrating high tracer recoveries and detection limits to pg/g (i...
February 14, 2017: Analytical Chemistry
Michael W Rosenzweig, Frank W Heinemann, Laurent Maron, Karsten Meyer
Reaction of trivalent [(((Ad,tBu)ArO)3tacn)U] (1) with 2,2'-bipyridine (bipy) yields [(((Ad,tBu)ArO)3tacn)U(bipy)] (2) and subsequent reduction of 2 with KC8 in the presence of Kryptofix222 furnishes [K(2.2.2-crypt)][(((Ad,tBu)ArO)3tacn)U(bipy)] (3). Alternatively, complex 3 can be synthesized from 1 by addition of [K(bipy)] in the presence of the cryptand. New complexes 2 and 3 are characterized by a variety of spectroscopic, electrochemical, and magnetochemical methods, single-crystal X-ray diffraction, computational methods, and CHN elemental analysis...
February 14, 2017: Inorganic Chemistry
Jörg Schaller, Britta Planer-Friedrich
Organic sediments in aquatic ecosystems are well known sinks for nutrients, silicon, and metal(loid)s. Organic matter-consuming organisms like invertebrate shredders, grazers, and bioturbators significantly affect element fixation or remobilization by changing redox conditions or binding properties of organic sediments. Little is known about the effect of filter feeders, like the zebra mussel Dreissena polymorpha, an invasive organism in North American and European freshwater ecosystems. A laboratory batch experiment exposing D...
February 7, 2017: Chemosphere
Laurent Pourcelot, Olivier Masson, Lionel Saey, Sébastien Conil, Béatrice Boulet, Nicolas Cariou
In the present paper the activity of uranium isotopes measured in plants and aerosols taken downwind of the releases of three nuclear fuel settlements was compared between them and with the activity measured at remote sites. An enhancement of (238)U activity as well as (235)U/(238)U anomalies and (236)U are noticeable in wheat, grass, tree leaves and aerosols taken at the edge of nuclear fuel settlements, which show the influence of uranium chronic releases. Further plants taken at the edge of the studied sites and a few published data acquired in the same experimental conditions show that the (238)U activity in plants is influenced by the intensity of the U atmospheric releases...
February 10, 2017: Journal of Environmental Radioactivity
U Iliyasu, Y V Ibrahim, Sadiq Umar, S A Agbo, Y Jibrin
Investigation of reactivity variation due to flooding of the irradiation channels of Nigeria Research Reactor (NIRR-1) a low power miniature neutron source reactor (MNSR) located at the Centre for Energy Research and Training, Ahmadu Bello University, Zaria Nigeria using the MCNP code for High Enrich Uranium (HEU) and Low Enrich Uranium (LEU) core has been simulated in this present study. In this work, the excess reactivity worth of flooding HEU core for 1 inner, 2 inner, 3 inner, 4 inner and all inner are 0...
February 9, 2017: Applied Radiation and Isotopes
Sean D Gates, William S Cassata
Radiochronometers are used to constrain the manufacturing and processing history of actinide materials for nuclear forensic investigations. This paper describes U-He ages and He diffusion kinetics obtained from a metallic, highly enriched uranium sample. The average U-He age is 8% older than the known casting date, which indicates that excess He is present and is likely due to incomplete degassing of pre-existing He during the casting process. Although the U-He age is older than expected, the accuracy is comparable to other chronometers that have been applied to this material...
December 20, 2016: Analytical Chemistry
Elisabete A De Nadai Fernandes, Camila Elias, Márcio Arruda Bacchi, Peter Bode
The quality of dog diets depends on adequate ingredients capable of providing optimal nutrition and free of contaminants, for promoting long-term health. Trace elements in 95 samples of dry food for dog puppies (n = 32) and adults (n = 63) of various brands were measured using instrumental neutron activation analysis (INAA). The mass fractions of most elements were within the permissible limits for dogs. Aluminum, antimony, and uranium presented fairly high levels in some samples, which may imply health risks...
February 12, 2017: Environmental Science and Pollution Research International
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