Formation of a sol of mixed U(IV) · U(VI) hydroxide in aqueous solutions with pH 1.5–4

containing U(IV) polymer start to form. With an increase in pH from 1.5 to 4 or in temperature, the induction period becomes shorter. Under anaerobic conditions, the colloidal solution is stable for more than a month. Centrifugation at 8000 rpm (5500g) allows separation of the colloidal particles from the liquid phase. The colloid slowly dissolves in mineral acids saturated with argon or in a K₂CO₃ solution, whereas precipitates of individual freshly prepared U(IV) and U(VI) hydroxides dissolve rapidly. Short UV irradia-of a UO₂(ClO₄)₂ solution saturated with argon and containing ethanol (pH 2.5) results in the appearance of U(V) which then disproportionates, and U(IV) forms with U(VI) a black colloid similar to that arising on mixing U(IV) and U(VI) solutions.     

Redox equilibrium U(IV) + 2Fe(CN) 63? ? U(VI) + 2Fe(CN) 64? in solutions of unsaturated heteropoly anions: Potentials of redox couples, stability of U(IV) complexes, reaction mechanism

The kinetics and equilibria of the reactions UO₂²⁺ + 2L + 2Fe(CN)₆⁴⁻ ⇄ UL₀ + 2Fe(CN)₆³⁻ in 0.1–1.0 M HCl solutions (ionic strength 1.0), where L is heteropoly anion of the composition P₂W₁₇O₆₁¹⁰⁻ or SiW₁₁O₃₉⁸⁻, were studied speelrophotometrically. Measurement of the redox potential of the ferri/rerrocyanide couple in acid solutions allowed estimation of the stability constants of the complxes U^IV(P₂W₁₇O₆₁)₂¹⁶⁻ and U^IV(SiW₁₁O₃₉)₂¹²⁻, equal in 1 M H⁺ solutions to 10^18.6 and 10^21.O, respectively. Accumulation of U^IVL₂ formed by reduction of UO₂²⁺ follows a first-order rate law, i.e., it involves the formation of UO₂⁺ which slowly reacts with L. The arising complex rapidly reacts with UO₂⁺. The loss of UL₂ occurs via formation of the complex of nonoxygenated U(V) with the heleropoly anion. Original Russian Text ? V.P. Shihv, A.B. Yusov. M.N. Sokolova, A.M. Fedoseev, 2008, published in Radiokhimiya, 2008, Vol. 50, No. 3, pp. 209–214.     

Interaction of An(VI) (An = U, Np, Pu) and Np(V) with 2,3-pyridinedicarboxylic (quinolinic) acid (H2Quin): Complexation in aqueous solutions, synthesis and structure of the complexes [UO2(HQuin)2], [(NpO2)2(HQuin)2(C6H4NO3)2]·2H2O, and [PuO2Quin(H2O)]

Complexation of An(VI) (An = U, Np, Pu), and Np(V) with 2,3-pyridinedicarboxylic (quinolinic, H₂Quin) acid in aqueous solutions was studied. Np(V) can form 1: 1 and 1: 2 complexes, and An(VI), also 1: 3 complexes (at pH ? 6 and [H₂Quin] ? 0.1 M). Quinolinate ion can coordinate to actinide(VI) and (V) ions in solutions in different modes. The apparent stability constants of the complexes in a wide pH range and the concentration stability constants of the An(VI) complexes were measured. In the series from Pu(VI) to U(VI), the stability of the complexes slightly increases. Crystalline complexes [UO₂(HQuin)₂], [(NpO₂)₂(HQuin)₂(HL)₂]·2H₂O (HL is N-protonated 2-hydroxypyridine-3-carboxylic acid anion), and [PuO₂Quin(H₂O)] were synthesized, and their structures were determined by single crystal X-ray diffraction. Different types of coordination of quinolinate ions to actinide ions are also observed in the crystalline complexes.     

Effect of salts on oxidation of Np(VI) with Fe(CN)<Stack><Subscript>6</Subscript><Superscript>3−</Superscript></Stack> Ions in 0.1–1 M alkali solutions

The potential of the Fe(CN)₆³⁻/Fe(CN)₆⁴⁻ couple in solutions containing 0.5–1 M alkali and high concentrations of Li, Na, and K salts was estimated potentiometrically. The reactions of Fe(CN)₆³⁻ with Np(VI) in such media were studied by spectrophotometry. In 0.5–1 M KOH + 7 M KF or 0.5–1 M KOH + 8 solutions, Np(VI) is oxidized to the heptavalent state with a small excess of Fe(CN)₆³⁻. In the presence of lithium or sodium salts, a larger excess of the oxidant is required for complete oxidation of Np(VI). Carbonate ions in concentrations exceeding 2 M prevent the Np(VI) oxidation.     

Novel Synthesis Methods of New Imidazole-Containing Coordination Compounds Tc(IV,V, VII)—Reaction Mechanism,Xrd and Hirshfeld Surface Analysis

In this work, we have proposed two new methods for the synthesis of [TcO₂L₄]⁺ (where L = imidazole (Im), methylimidazole (MeIm)) complexes using thiourea (Tu) and Sn(II) as the reducing agents. The main and by-products of the reactions were determined, and possible reaction mechanisms were proposed. We have shown that the reduction of Tc(VII) with thiourea is accompanied by the formation of the Tc(III) intermediate and further oxidation to Tc(V). The reaction conditions’ changing can lead to the formation of Tc(VII) and Tc(IV) salts. Seven new crystal structures are described in this work: Tc(V) complexes, salts with Tc(VII) and Tc(IV) anions. For the halide salts of Tu the cell parameters were determined. In all of the obtained compounds, except for [TcO₂(MeIm)₄]TcO₄, there are π–stacking interactions between the aromatic rings. An increase in the anion size lead to weakening of the intermolecular interactions. The halogen bonds and anion-π interactions were also found in the hexahalide-containing compounds. The Hirshfeld surface analysis showed that the main contribution to the crystal packing is created by the van der Waals interactions of the H···H type (42.5–55.1%), H···C/C···H (17.7–21.3%) and hydrogen bonds, which contribute 15.7–25.3% in total.     

Crystal Structure of An(VI) Complexes with Succinate Anions, [PuO2(C4H4O4)(H2O)] and Cs2[(AnO2)2(C4H4O4)3]·H2O (An = U,Np, Pu)

Radiochemistry - Actinide(VI) complexes with succinate anions [PuO2(succ)(H2O)] and Cs2[(AnO2)2(succ)3]·H2O (An = U, Np, Pu), where succ = [C4H4O4]2 ?, were synthesized and studied by...     

Estimating Synergetic Openness of Industrial Enterprise Management Systems

The problem of comprehensive assessment of available enterprise management systems from implementation and application viewpoint is discussed. The degree of information system’s synergetic openness, which described system’s ability to respond to external users’ requests by means of built-in self-organization mechanisms and tools, is offered as an integrated quality index. This complex index depends of partial factors, describing system’s adaptability and integrability. With the help of comprehensive assessment the available ERP systems are compared, and the need in taking into account industrial user’s specific features during system selection is demonstrated.     

Preparation of Macrocrystalline Tungsten-Based Alloys by Electron-Beam Floating Zone Melting

Inorganic Materials - Macrocrystalline tungsten alloys containing 1, 3, and 5 at % alloying additives (Re, Mo, Ta, Cr, Fe, and V) have been prepared by electron-beam floating zone melting. The...     

Kinetics of Pu(VI) Reaction with Ethylenediaminetetraacetic Acid

Radiochemistry - The spectrophometric method was used to examine the stoichiometry of the reaction of Pu(VI) reduction by EDTA ions in 0.05–0.5 M HClO4 solutions at a temperature of 23°C...