Laser spectroscopic studies of interactions of UVI with bacterial phosphate species

We have investigated the interactions of UVI with two bacterial phosphate-containing species: Gram-positive Bacillus sphaericus and Gram-negative Pseudomonas aeruginosa. The Gram-positive B. sphaericus was investigated by using Raman spectroscopy and time-resolved laser-induced fluorescence spectroscopy (TRLFS). We found that living cells, spores, and intact heat-killed cells complexed UVI (pH 4.5) through phosphate groups bound to their surfaces, while decomposed cells released H2PO4- and precipitated UVI as UO2(H2PO4)2. TRLFS of UVI showed that Gram-negative P. aeruginosa--genetically engineered to accumulate polyphosphate, subsequently degrade it, and secrete phosphate--precipitated UVI quantitatively at pH 4.5. The same bacterial strain, not induced to secrete phosphate, sorbed only a small amount of UVI.     

Electron probe microanalysis of dried biological substances

In the present study electron probe X-ray microanalysis (EPMA) was used to examine the elemental contents in samples of biological molecules from aqueous solutions and of cultured cells. To preserve the contents of diffusible elements the freeze-drying technique was applied as a preparative procedure. The resulting powders were then formed into small tablets, weighing about 0.1 mg, which were analyzed with a wavelength-dispersive spectrometer (WDS). Using tablets, the total concentration of different elements was measured in biological substances isolated fromGalleria mellonella, and cells taken from a culture ofChlorella vulgaris treated with uranium nitrate.     

铀(Ⅵ)的二溴水杨醛缩二胺类双希夫碱及溶剂三元配合物的合成和表征

铀（Ⅵ）的二溴水杨醛缩二胺类双希夫碱及溶剂三元配合物的合成和表征郑庚修＊毕彩丰张家祥王秋芬张广友（山东建材学院应用化学系，济南２５００２２）关键词：硝酸铀双希夫碱三元配合物关于铀与希夫碱的配合物的结构、萃取等研究已有报道。结构研究发现：铀（Ⅵ）盐可以...     

酰胺类萃取剂的模糊聚类分析

萃取剂的结构与其萃取性能(如分配比、分离比、萃取热力学常数)相关,但因研究对象的繁纷复杂以及所研究的对象的关系中的不确定性,采用精确关联的方法有一定困难。作者曾将模糊聚类分析的方法用于中性磷类萃取剂,本文再次将这一方法用于酰胺类萃取剂。     

The Simultaneous Determination of Trace Dy,Eu, Gd and Sm in Nuclear Grade Uranium Oxide by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES)

A method for the simultaneous determination of trace Dy, Eu, Gd and Sm in nuclear grade uranium oxide by Inductively Coupled Plasma Atomic Emission Spectrometry has been developed. The process of uranium extraction and ICP/AES optimization are investigated. The detection limits of Dy, Eu, Gd and Sm are 0.003, 0.002, 0.006 and 0.010 μg/ml respectively, and more than 90% recovery can be obtained.     

An overview of studies on the highly dispersed uranium oxide species occluded within mesoporous MCM-41 and MCM-48 host materials

In this article we have consolidated our recent studies on anchoring of uranyl groups and encapsulation of highly dispersed nano-particles of -U₃O₈ in mesoporous MCM samples. The size of uranium oxide crystallites and the binding of uranyl groups at framework sites of host matrix depended on the preparation method, viz. wet impregnation, exchange of template cations, and the hydrothermal route. These uranium species contributed individually to the catalytic oxidation of organic molecules, such as methanol, toluene and benzyl alcohol; the uranyl groups playing a more important role at lower reaction temperatures. Also, the size and the lattice oxygen of uranium oxide crystallites played a vital role, not only in the lowering of reaction onset temperature but also in deciding the nature and the reactivity of the transient surface species formed during the oxidation of above mentioned organics. For instance, the results of in situ IR spectroscopy experiments have shown that while larger-size U₃O₈ crystallites help in the growth of certain oxymethylene (–OCH₂) and polymerized oxymethylene (–OCH₂)_n species, adsorption of methanol on smaller size particles helped in the additional formation of formate-type complexes. Thus, a relationship was found between the size of uranium oxide crystallites, the nature of the transient species formed and the catalytic conversion of methanol to form CO₂, CO and methane. In addition, the uranyl ions anchored within the pore system of host matrix are found to serve as efficient heterogeneous photocatalysts for the sunlight-assisted deep oxidation of organic molecules in the vapor phase and at room temperature. The reaction mechanisms, accounting for the catalytic properties of occluded UO_x species without and in the presence of radiation, are discussed in the light of the above mentioned results.     

伯胺N~1~9~2~3萃取硫酸铀酰的机理研究

研究了伯胺N~1~9~2~3的正庚烷溶液从硫酸介质中萃取硫酸铀酰的机理。认为伯胺N~1~9~2~3的硫酸盐在有机相中形成了反向胶束(或胶团),并由红外光谱和透射电镜佐证。伯胺N~1~9~2~3和铀酰形成的萃合物主要存在于反向胶束准相中。可以较好地解释用斜率法无法解释的实验事实。     

Beiträge zur Kristallchemie der Urantelluride. II. Die Kristallstruktur des Diuranpentatellurids U2Te5

Contributions to the Crystal Chemistry of Uranium Tellurides. II. The Crystal Structure of Diuranium Pentatelluride U₂Te₅ Via chemical transport reactions with TeBr₄ as transporting agent single crystals of the title compound up to a size of 5 mm were available from the elements. The analysis by atomic emission spectrometry gave UTe_2.52(4). By X-ray single crystal structure analysis we found that U₂Te₅ crystallizes monoclinic (space group C2/m, Z = 4) with a = 3443.3(5) pm, b = 418.65(3) pm, c = 607.97(6) pm and β = 95.35(1)º in a new structure type. The layer structure is built up by bicapped trigonal prisms, one half as isolated building units, the other connected via faces as fourfold capped biprisms. A structural relationship of diuranium pentatelluride to the adjacent phases in the phase diagram U? Te can be expressed by the formulation as UTe₂ · UTe₃.     

Determination of trace impurities in electronic grade quartz: Comparison of inductively coupled plasma mass spectroscopy with other analytical techniques

An analytical procedure for the determination of uranium and thorium in the sub-ng/g range as well as of other trace elements in the ng/g to g/g range in high purity quartz samples is described. The results obtained by inductively coupled plasma mass spectroscopy (ICP-MS) are compared to those obtained by other analytical techniques (instrumental neutron activation analysis, INAA; flame atomic absorption spectrometry, AAS; Zeeman graphite furnace atomic absorption spectrometry, ZGFAAS; total reflection X-ray fluorescence analysis, TRFA; direct current arc optical emission spectrometry, DC-arc OES; and X-ray fluorescence analysis, XRFA). For the ICP-MS measurements, the decomposition of the samples is carried out with HF/HNO₃/H₂SO₄-mixtures. The results obtained by the different methods show reasonable agreement. For uranium and thorium, ICP-MS proves to be the most sensitive method: detection limits of about 50 pg/g can be achieved for both elements.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

Use of Benzoylthiourea Immobilized on Silica Gel for Separation and Preconcentration of Uranium(VI)

Benzoylthiourea immobilized on silica gel was prepared by two-step post-synthesis modification. The capacity of the chelating silica gel, which was characterized by FTIR, was 3.21 mmol · g⁻¹. The separation and enrichment of uranium(VI) from solutions was investigated. Effective extraction conditions were optimized in both batch and column methods prior to determination by spectrophotometry using arsenazo(III). The optimum pH range for quantitative adsorption is 4–7. Quantitative recovery of U(VI) was achieved by stripping with 0.1 mol · L⁻¹ HCl. The sorption capacity of modified silica gel was 0.85 mmol · g⁻¹ uranium(VI). Recovery of U(VI) was 99.1 ± 2.3% with a detection limit of 2 μg · L⁻¹. The preconcentration factor was 250, and the relative standard deviation was 1.53% for a 1 μg · L⁻¹ U(VI) solution. The method was used for the determination of uranium in synthetic samples and a soil sample.