Ruthenium speciation and distribution in the environment: A review.

The review focuses on speciation and migration of anthropogenic ruthenium (Ru) originated from nuclear industry releases and presents updated information regarding Ru in the environment. It provides analysis of the main pathways of Ru species distribution in the aqueous and terrestrial environment, starting from its natural occurrence, generation and release from anthropogenic sources, predominant speciation, and ending with bioaccumulation, which can be directly or indirectly related to human health. Literature sources belonging to the post-Chernobyl time frame were preferentially considered, in which Ru-103 and Ru-106 are the major fission isotopes studied due to their traceability in the environment and their relatively long half-lives.

Extraction of Nitric Acid and Uranium with DEHiBA under High Loading Conditions.

The mechanism by which high concentrations (1.5 M in -dodecane) of ,-di-2-ethylhexyl-isobutyramide (DEHiBA) extracts HNO and UO(NO) is under examination. Most prior studies have examined the extractant and the mechanism at a concentration of 1.

Equatorial Electronic Structure in the Uranyl Ion: CsUOCl and CsUOBr.

Electric field gradient (EFG) tensors in the equatorial plane of the linear UO ion have been measured by nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) experiments and computed by relativistic Kohn-Sham methods with and without environment embedding for CsUOCl and CsUOBr. This approach expands the possibilities for probing the electronic structure in uranyl complexes beyond the strongly covalent U-O bonds. The combined analyses find that one of the two largest principal EFG tensor components at the halogen sites points along the U-X bond (X = Cl, Br), and the second is parallel to the UO ion; in CsUOCl, the components are nearly equal in magnitude, whereas in CsUOBr, due to short-range bromide-cesium interactions, the equatorial component is dominant for one pair of Br sites and the axial component is larger for the second pair.

Identification and Quantification of Technetium Species in Hanford Waste Tank AN-102.

Technetium-99 (Tc), a high yield fission product generated in nuclear reactors, is one of the most difficult contaminants to address at the U.S. Department of Energy Hanford, Savannah River, and other sites.

Sensor Fusion: Comprehensive Real-Time, On-Line Monitoring for Process Control via Visible, Near-Infrared, and Raman Spectroscopy.

On-line monitoring based on optical spectroscopy provides unprecedented insight into the chemical composition of process streams or batches. Amplifying this approach through utilizing multiple forms of optical spectroscopy in sensor fusion can greatly expand the number and type of chemical species that can be identified and quantified. This is demonstrated herein, on the analysis of used nuclear fuel recycling streams: highly complex processes with multiple target and interfering analytes.

Spontaneous redox continuum reveals sequestered technetium clusters and retarded mineral transformation of iron.

The sequestration of metal ions into the crystal structure of minerals is common in nature. To date, the incorporation of technetium(IV) into iron minerals has been studied predominantly for systems under carefully controlled anaerobic conditions. Mechanisms of the transformation of iron phases leading to incorporation of technetium(IV) under aerobic conditions remain poorly understood.

Evolution of Acid-Dependent Am and Eu Organic Coordination Environment: Effects on the Extraction Efficiency.

Coordination of trivalent lanthanide and actinide metal ions by lipophilic diglycolamides and phosphonic acids has been proposed for their separation through extraction from aqueous nitric acid solutions. However, the nature of M coordination complexes in these combined solvent systems is not well understood, resulting in low predictability of their behavior. This work demonstrates that a combination of ,,','-tetrakis(2-ethylhexyl)diglycolamide (T2EHDGA) and weakly acidic 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) in -dodecane exhibits a complicated extraction mechanism for Eu and Am, which continuously evolves as a function of the aqueous phase acidity.

Redox-Based Electrochemical Affinity Sensor for Detection of Aqueous Pertechnetate Anion.

Rapid, selective, and in situ detection of pertechnetate (TcO) in multicomponent matrices consisting of interfering anions such as the ubiquitous NO and Cl or the isostructural CrO is challenging. Present sensors lack the selectivities to exclude these interferences or the sensitivities to meet detection limits that are lower than the drinking water standards across the globe. This work presents an affinity-based electrochemical sensor for TcO detection that relies on selective reductive precipitation of aqueous TcO induced by a 1,4-benzenedimethanethiol capture probe immobilized on an electrode platform.

Author Correction: Closing the Nuclear Fuel Cycle with a Simplified Minor Actinide Lanthanide Separation Process (ALSEP) and Additive Manufacturing.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Closing the Nuclear Fuel Cycle with a Simplified Minor Actinide Lanthanide Separation Process (ALSEP) and Additive Manufacturing.

Expanded low-carbon baseload power production through the use of nuclear fission can be enabled by recycling long-lived actinide isotopes within the nuclear fuel cycle. This approach provides the benefits of (a) more completely utilizing the energy potential of mined uranium, (b) reducing the footprint of nuclear geological repositories, and (c) reducing the time required for the radiotoxicity of the disposed waste to decrease to the level of uranium ore from one hundred thousand years to a few hundred years. A key step in achieving this goal is the separation of long-lived isotopes of americium (Am) and curium (Cm) for recycle into fast reactors.

Spectroscopic Characterization of Aqua [ fac-Tc(CO)] Complexes at High Ionic Strength.

Understanding fundamental Tc chemistry is important to both the remediation of nuclear waste and the reprocessing of nuclear fuel; however, current knowledge of the electronic structure and spectral signatures of low-valent Tc compounds significantly lags behind the remainder of the d-block elements. In particular, identification and treatment of Tc speciation in legacy nuclear waste is challenging due to the lack of reference data especially for Tc compounds in the less common oxidation states (I-VI). In an effort to establish a spectroscopic library corresponding to the relevant conditions of extremely high ionic strength typical for the legacy nuclear waste, compounds with the general formula of [ fac-Tc(CO)(OH)(OH) ] (where n = 0-3) were examined by a range of spectroscopic techniques including Tc/C NMR, IR, XPS, and XAS.

Theoretical Modeling of (99)Tc NMR Chemical Shifts.

Technetium-99 (Tc) displays a rich chemistry due to its wide range of accessible oxidation states (from -I to +VII) and ability to form coordination compounds. Determination of Tc speciation in complex mixtures is a major challenge, and (99)Tc nuclear magnetic resonance (NMR) spectroscopy is widely used to probe chemical environments of Tc in odd oxidation states. However, interpretation of (99)Tc NMR data is hindered by the lack of reference compounds.

Neighboring π-Amide Participation in Thioether Oxidation: Conformational Control.

The electrochemical oxidation of thioethers is shown to be facilitated by neighboring amide participation. (1)H NMR spectroscopic analysis in acetonitrile solution of two conformationally constrained compounds with such facilitation shows that two-electron participation by the amide π2 orbital can occur to stabilize the developing sulfur radical cation.

Two organophosphorus pesticides: methyl parathion and dicapthon.

Structural studies performed in this laboratory of organophosphorus pesticides continue with these related compounds. The -NO2 groups of methyl parathion (systematic name: dimethyl 4-nitrophenyl phosphorothioate, C8H10NO5PS) and dicapthon (systematic name: 2-chloro-4-nitrophenyl dimethyl phosphorothioate, C8H9ClNO5PS) make dihedral angles of 10.67 (8) and 5.

Intramolecular electron transfer in bipyridinium disulfides.

Reductive cleavage of disulfide bonds is an important step in many biological and chemical processes. Whether cleavage occurs stepwise or concertedly with electron transfer is of interest. Also of interest is whether the disulfide bond is reduced directly by intermolecular electron transfer from an external reducing agent or mediated intramolecularly by internal electron transfer from another redox-active moiety elsewhere within the molecule.

IMPROVED SYNTHESIS OF 10-(2-ALKYLAMINO-2-OXOETHYL)-1,4,7,10-TETRAAZACYCLODODECANE-1,4,7-TRIACETIC ACID DERIVATIVES BEARING ACID-SENSITIVE LINKERS.

Alkylation of the hydrobromide salts of 1,4,7-tris(methoxycarbonylmethyl)-1,4,7,10-tetraazacyclododecane and 1,4,7-tris(ethoxycarbonylmethyl)-1,4,7,10-tetraazacyclododecane with appropriate α-bromoacetamides, followed by hydrolysis, provides convenient access to 10-(2-alkylamino-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid derivatives that contain acid-sensitive functional groups. The utility of the method is demonstrated by improved syntheses of two known DOTA monoamides bearing acid-sensitive ω-tritylthio alkyl chains in much higher yields based on cyclen as the starting material.

3-(4-Bromo-phen-yl)-1-butyl-5-[1-(2-chloro-6-methyl-phen-yl)-1H-tetra-zol-5-yl]imidazolidine-2,4-dione.

In the title mol-ecule, C21H20BrClN6O2, the chloro-substituted benzene ring forms a dihedral angle of 77.84 (7)° with the tetra-zole ring and the bromo-substituted ring forms a dihedral angle of 43.95 (6)° with the imidazole ring.

Importance of co-donor field strength in the preparation of tetradentate α-diimine nickel hydrosilylation catalysts.

Although bis(α-diimine)Ni complexes were prepared when amine-substituted chelates were added to Ni(COD)2, the incorporation of strong-field phosphine donors allowed the isolation of (κ(4)-N,N,P,P-DI)Ni hydrosilylation catalysts. The crystallographic investigation of two different (κ(4)-N,N,P,P-DI)Ni compounds revealed that the geometry about nickel influences the observed degree of α-diimine reduction.

tert-Butyl 4-(3,4-dichloro-anilino)piperidine-1-carboxyl-ate.

In the title compound, C(16)H(22)Cl(2)N(2)O(2), the substituted piperidine ring adopts a chair conformation with both substituents in equatorial positions. In the crystal, N-H⋯O and C-H⋯O hydrogen bonds connect mol-ecules into ribbons along the a-axis direction.