Selective Recovery of Chromium from Precipitates Containing d Elements and Actinides: I. Effect of O2

Oxidation of Cr(III) hydroxides, double Fe(III)-Cr(III) hydroxides, and some examples of spinel phases NiCr₂O₄ and Fe(Cr,Fe)₂O₄ in alkaline suspensions (0.2-0.5 M NaOH) under the action of air and pure oxygen (1-3 atm) was studied. The reaction rate increases with increasing concentration of alkali, temperature, and oxygen pressure. Under these conditions, Pu(IV) sorbed on chromium hydroxides is not oxidized with oxygen and remains in the precipitate.     

Selective Recovery of Chromium from Precipitates Containing d Elements and Actinides: III. Effect of S2O82-

Reaction of Cr(III) hydroxides and mixed Fe(III)-Cr(III) and Ni(II)-Cr(III) hydroxides with persulfate ion in alkaline solutions was studied by spectrophotometry. The Cr(VI) yield (at oxidant deficiency) corresponds to the S₂O₈ ^{2 -} : Cr(VI) molar ratio close to 1.5. The initial reaction rate V ₀ is described by the kinetic equation -d[Cr(III)]/d = k[Cr(III)][S₂O₈ ^{2 -}][NaOH]. The activation energy is 53 kJ mol^{- 1} within the 41.5-95°C range. V ₀ is higher than the rate of thermal decomposition of persulfate ion, i.e., Cr(III) reacts directly with S₂O₈ ^{2 -}. Oxidation of NiCr₂O₄·nH₂O and mixed Fe(III)-Cr(III) hydroxides proceeds faster than oxidation of pure Cr(III) hydroxide. This is due to the catalytic effect of Fe(III) and Ni(II). Additions of Co(II) and Cu(II) also accelerate the process. Pu(IV) in alkali solution under the action of persulfate is converted into a more soluble oxidized species, which can be reduced back to Pu(IV) with appropriate reductants.     

Effect of annealing on d.c. conductivity of V2O5-SnO-TeO2 glasses

The d.c. conductivity (σ) of V₂O₅-SnO-TeO₂ glasses prepared by the press-quenching method was studied at temperatures from room temperature (RT) to 473 K, and the effect of annealing on σ was investigated. The conductivity of 50V₂O₅·20SnO·30TeO₂ glass was determined to be 3.98×10⁻⁴ Scm⁻¹ at 473 K and was unchanged for annealing (6–48 h) at 493 K, lower than T_g = 501 K, while its density increased with annealing time. These glasses were found to be n-type semiconductors, and the conduction was confirmed to be due to adiabatic small polaron hopping for V₂O₅ ≧ 50 mol%, and non-adiabatic for V₂O₅ < 50 mol%. The activation energy for conduction, W, decreased with annealing time. Variations in oxygen molar volume of the glasses with annealing time inferred a change in glass structure, from loosely to closely packed, resulting in a decrease in vanadium ion spacing with annealing. This caused an increase in the polaron band width, producing a decrease in polaron hopping energy and W. The effect of annealing time on the density of 50V₂O₅·20SnO·30TeO₂ glass was explained adequately by Winter's formula.     

Behavior of Np(V) in HCOOH Solutions Containing H2O and HClO4

Radiochemistry - Spectrophotometry has been used to examine the kinetics of Np(V) disproportionation in HCOOH solutions containing H2O and HClO4 at temperatures of 20–45°C. The reaction...     

Lower Oxidation States of f Elements: I. Preparation and Identification of Actinides and Lanthanides in Lower Oxidation States

Studies on the title subject, published mainly in the second half of the XX century and made both with macroamounts of lanthanides (Ln) and actinides (An) and with micro- and ultramicroamounts of radionuclides of these elements, are considered. Procedures for preparing f elements in lower oxidation states in solutions, melts, and solid matrices and methods for identifying these states (electrochemistry, spectrometry, high-temperature extraction, cocrystallization, etc.) are discussed.     

Synthesis and structural study of new potassium uranyl selenates K2(H5O2)(H3O)[(UO2)2(SeO4)4(H2O)2](H2O)4 and K3(H3O)[(UO2)2(SeO4)4(H2O)2](H2O)5

Single crystals of new uranyl selenates K₂(H₅O₂)(H₃O)[(UO₂)₂(SeO₄)₄(H₂O)₂](H₂O)₄ (1) and K₃(H₃O)[(UO₂)₂(SeO₄)₄(H₂O)₂](H₂O)₅ (2) were prepared by isothermal evaporation at room temperature. The crystal structure of 1 was solved by the direct method [C2/c, a = 17.879(5), b = 8.152(5), c = 17.872(5) Å, β = 96.943(5)°, V = 2585.7(19) ų, Z = 4] and refined to R ₁ = 0.0449 (wR ₂ = 0.0952) for 2600 reflections with |F _o| ≥ 4σ _F . The structure of 2 was solved by the direct method [P2₁/c, a = 17.8377(5), b = 8.1478(5), c = 23.696(1) Å, β = 131.622(2)°, V = 2574.5(2) ų, Z = 4] and refined to R ₁ = 0.0516 (wR ₂ = 0.1233) for 4075 reflections with |F _o| ≥ 4σ _F . The structures of 1 and 2 are based on [(UO₂)₂(SeO₄)₄(H₂O)₂]^4? layers. The charge of the inorganic layer is compensated by potassium and oxonium ions arranged in the interlayer space. Each K ion is surrounded by seven O atoms belonging to uranyl selenate layers and water molecules, so that it binds with each other the adjacent uranyl selenate structural elements.     

Preparation of stone-shaped CuBi2O4 by solid phase method and H2O2 assisted visible light degradation for orange II

CuBi₂O₄ is widely used in photocatalytic degradation for pollutants in water due to its strong visible light response characteristics, excellent chemical stability, non-toxic, and low cost. Here, stone-shaped CuBi₂O₄ was prepared with CuO and Bi₂O₃ as raw materials by high temperature solid phase. The effect of calcined temperature and time on the product was discussed. This material was analyzed and discussed by XRD, SEM, XPS, and DRS, and the visible light activity of degradation for Orange II was explored. The results showed that the absorption edge of prepared CuBi₂O₄ expands to the visible region, and the band gap was about 1.77 eV. The photocatalytic degradation rate of Orange II was 42.6% under the optimal conditions. After H₂O₂ assisted, the degradation rate was more than 2 times, and repeated experiments verified that the prepared catalysts had high stability. Finally, a reasonable mechanism of H₂O₂ assisted degradation enhancement is proposed. This work gives new ideas for the preparation of new and efficient catalytic materials.

     

Crystallization of AlPo4-5 from a system-1.5 (C3H7)3N.1.0Al2O3.1.0 P2O5. 40.0 H2O : Characterization of the products of crystallization

Crystallization of AlPO₄-5 from a gel of composition 1.5 Pr₃N (tripropylamine)· 1.0 Al₂O₃· 1.0 P₂O₅· 40.0 H₂O has been investigated by carrying out the hydrothermal synthesis of the crystalline aluminophosphate in a closed stainless steel pressure bomb at 423 K for different durations of the crystallization (0–48 h). The solid products obtained during the course of crystallization have been characterized thoroughly for their crystallinity (as AlPO₄-5), crystal size and morphology, N₂-sorption capacity (at 78 K and relative pressure of 0.3), thermal analysis, site energy distribution by TPD of pyridine, acidity by chemisorption of pyridine at 673 K and also for their catalytic activity in cumene cracking and o-xylene isomerization reactions at 673 K. The aluminophosphate formed at the different crystallization periods differ from each other largely in these properties. The optimum crystallization period for the synthesis of AlPO₄-5 is about 24 h.     

Optical and electrical properties of reactively d.c. magnetron-sputtered In2O3:Sn films

The deposition of transparent conductive indium oxide doped with tin is investigated. Characterization of the d.c. magnetron-sputtered films shows that it is possible to obtain transparent conductive films from an InSn alloy by sputtering in a reactive atmosphere. This deposition method in combination with an appropriate anneal results in a very low light absorption and a high electrical conductivity of the films. In this paper the two-step deposition technique and the electrical and optical properties of the deposited transparent and conductive layers are described.     

Ag与Ag2O协同增强TiO2光催化制氢性能的研究

本研究采用两步法制备了电子助剂Ag和界面活性位点Ag₂O共修饰的高效TiO₂光催化剂(TiO₂/Ag-Ag₂O): 首先用光沉积法将Ag负载在TiO₂表面(TiO₂/Ag), 再经过低温煅烧法使部分Ag原位生成Ag₂O。紫外光照射TiO₂时, 激发产生的电子被助剂Ag捕获后快速传输到Ag₂O上, 电子把Ag₂O界面产氢活性位点从溶液中所捕获的氢离子还原成氢气, Ag和Ag₂O的协同作用加快了TiO₂上光生电子的转移和界面产氢反应, 从而提高了TiO₂/Ag-Ag₂O制氢性能。在300 ℃煅烧温度下制备的TiO₂/Ag-Ag₂O光催化剂制氢速率最高, 达到75.20 μmol/h, 分别是TiO₂(3.59 μmol/h)和TiO₂/Ag(41.13 μmol/h)的21.0倍和1.8倍。本研究为光催化制氢材料的设计和制备提供了有益的参考。     

Effect of H2O on the Ionic conductivity of sodium beta-alumina

The effect of water molecules on the ionic conductivity of sodium betaalumina single crystals was investigated. Water molecules intercalated in the conducting plane lower than the conductivity by as much as a factor of two.     

Na2O的含量对MoSi2/Oxide系发热元件材料力学性能的影响

对比了脱Na处理工艺前后Na₂O含量变化对MoSi₂/Oxide系发热元件材料力学性能的影响.研究结果表明,虽然Na₂O含量的高低对发热体材料常温力学性能影响不大,但是对发热元件材料高温力学性能有重要影响.主要表现在:经1573K热处理100h后脱Na材料仍拥有很高的强度和韦伯分布;而且经过真空脱Na后材料的高温蠕变特性也有了明显改善,在1243和1303K的条件下脱Na材料的蠕变速率分别是未脱Na材料的2/5和1/3以下.另外,Na₂O含量对材料延性脆性转变温度(BDTT)也有重要影响,脱Na材料的BDTT较未脱Na材料升高约100K.     

Synthesis,crystal structure and solubility of C6H14N4O2,C4H4O4,2H2O

Synthesis, crystal structure and solubility of a new non-linear optical material l-arginine maleate dihydrate have been reported here. From the solubility studies with different solvents, water was found to be the most suitable one. Title compound crystallized in the triclinic space group P1 with Z=1 and unit cell dimensions a=5.264(3) Å, b=8.039(3) Å, c=9.784(3) Å, α=106.19(3)°, β=97.24(3)°, γ=101.66(2)°. The present complex of l-arginine contains a positively charged zwitterionic arginine molecule and a negatively charged semi-maleate ion. The molecules are held together by a three-dimensional network of hydrogen bonds.     

Application of Box-Wilson experimental design method for the photodegradation of bakery's yeast industry with UV/H2O2 and UV/H2O2/Fe(II) process

Decolorization and mineralization of bakery's yeast industry effluent by photochemical advanced oxidation processes (AOPs) utilizing UV with hydrogen peroxide and Photo-Fenton, were investigated in a laboratory scale photo-reactor equipped with a 16 W low-pressure mercury vapor lamp. The Box-Wilson experimental design method was employed to evaluate the effects of major process variables (e.g. pH, oxidant dose, and irradiation time) on the decolorization efficiency. Response function coefficients were determined by regression analysis of the experimental data and prediction results agreed with the experimental results. The optimum hydrogen peroxide concentration and irradiation time were found to be 5 mM and 50 min at pH 3, respectively, for UV/H2O2 process. In the Photo-Fenton process application, maximum decolorization efficiency (96.4%) was obtained at the optimum reaction conditions that were 100 mM H2O2 and 1 mM Fe(II) doses at pH 3, and 10 min of irradiation time.     

Recovery of Pd from Spent Fuel: 2. Sorption Recovery of Pd from Nitric Acid Solutions on Anion-Exchange Resins

Recovery of Pd from nitric acid solutions on various anion-exchange resins is studied. The effects of the HNO₃ concentration, temperature, and aminoacetic acid on the desorption of Pd are examined. Results of the experiments on Pd recovery from actual solutions from spent fuel reprocessing are reported.__________Translated from Radiokhimiya, Vol. 47, No. 4, 2005, pp. 339–342.Original Russian Text Copyright © 2005 by Korolev, Pokhitonov, Gelis, Milyutin.     

Specific Features of Anodic Dissolution of Copper in H2SO4 + H2O and H2SO4 + CuSO4 + H2O Systems

We investigate anodic dissolution of copper in H₂SO₄ + H₂O and H₂SO₄ + H₂O + CuSO₄ systems, which model solutions for the electrochemical production of copper (+2) sulfate. Ultimate densities of anodic current in the temperature range 20–80°C for a voltage up to 8 V were found. We show that a concentration of copper ions ( Cu²⁺) of 1.5–2.0 moles/liter in the anolyte is the limiting one in the electrochemical production of solutions of copper (+2) sulfate.     

氨解草酸氧钒制备纳米氮化钒粉体

首次采用氨解草酸氧钒（VOC2O4·H2O）前驱体的方法成功制备出了平均粒径50nm左右的立方相VN粉体.通过X射线衍射测试分析了温度、时间和氨气流量对氮化钒形成的影响。用透射电镜（TEM）观察和分析了氮化钒粉体的形貌和结构。实验结果表明，在600-850℃前驱体均能氨解戌VN，随氨解温度的升高，VN形成的时间显著缩短，750℃的温度下，10min就可以氨解完全。氨气流量可控制在40ml／min以上，表明该方法具有氨解温度低、氨气流量少和产物纯度高的特点。     

A new high-nitrogen compound [Mn(ATZ)(H2O)4] x 2H2O: synthesis and characterization

A new high-nitrogen compound [Mn(ATZ)(H(2)O)(4)] x 2H(2)O (ATZ=5,5-azotetrazolate) was synthesized. Crystal structure and elemental, IR and thermal analyses were investigated in the present work. It crystallized in triclinic space group P-1 with lattice parameters a=6.304(2)A, b=7.004(2)A, c=7.921(3)A, alpha=76.114(5) degrees , beta=74.023(5) degrees , gamma=69.254(4) degrees . TG-DTG and DSC measurements are employed to postulate the thermal decomposition mechanism. The thermal decomposition kinetics of the main exothermic reaction was investigated by non-isothermal method and obtained its enthalpy of decomposition and the probable kinetic mechanism. An attempt was made to incorporate the relation between thermal stability and the structure.