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Abstract  

Extraction studies of uranium(VI) and molybdenum(VI) with organophosphoric, phosphinic acid and its thiosubstituted derivatives have been carried out from 0.1–1.0M HCl solutions. The extracted species are proposed to be UO2R2 and MoO2 CIR on the basis of slope analysis for uranium(VI) and molybdenum(VI), respectively. The extraction efficiencies of PC-88A, Cyanex 272, Cyanex 301 and Cyanex 302 in the extraction of molybdenum(VI) and uranium(VI) are compared. Synergistic effects have been studied with binary mixtures of extractants. Separation of molybdenum(VI) from uranium(VI) is feasible by Cyanex 301 from 1M HCl, the separation factor log being 2.3.

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Abstract  

From a model for isothermal oxidation kinetics in nanosized ferrite spinels based on a diffusion-induced stress effect, the authors present a modeling of the DTG curves for the oxidation of Fe2+ and Mo3+ cations on octahedral sites of a molybdenum ferrite. This has been made by considering that the chemical diffusion coefficient is given by the relation
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\tilde D = D_o \exp \left( {\frac{{E'_{\text{a}} + pV_{\text{a}} }}{{RT}}} \right)$$ \end{document}
, when D o is a pre-exponential factor, E a an activation energy and V a an activation energy induced by the oxidation.
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Abstract  

99Mo−99mTc generators were prepared starting from irradiated molybdenum metal instead of MoO3 in order to use reactor irradiation space more economically. The adsorption of molybdenum as sodium molybdate on different kinds of alumina was investigated. The effect of the pH of the column and the aqueous phase concentration of molybdenum were studied and related to the elution yield of99mTc. A study of the radiation damage effect indicated that generators having a high elution efficiency of 90% could be prepared in the 100–600 mCi range. The losses of99Mo were minimized to 10−5-10−4% and those of alumina to 2–5 μg/ml eluate.

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The reaction between potassium iodate and molybdenum(VI) oxide in mixtures of different mole ratios has been investigated employing TG and DTA techniques in static air atmosphere. The products are characterised by infrared spectroscopy, chemical analysis and X-ray diffraction studies. The studies indicate the formation of mono-, di-, tri- and tetramolybdates of potassium from mixtures with 2∶1, 1∶1, 2∶3 and 1∶2 mole ratios of KlO3∶MoO3. The kinetics of the reaction was followed and the energy of activation values were computed.

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Abstract  

A method for arsenic, antimony, selenium and molybdenum determination in water, loess and volcanic glasses, by radiochemical neutron activation analysis based on coprecipitation with Bi2S3 in hydrochloric medium, is described. The results of application to a study of natural contamination in the south-eastern region of the province of Córdoba, Republic of Argentina, are presented and discussed.

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Abstract  

The purpose of the present paper is to suggest a method for determining the235U abundance in uranium samples (compounds, metallic alloys or other uranium materials, where this element may be natural or not) through a particular application of neutron activation analysis, based on the fission interference by molybdenum. The method lies on an a priori calibration with natural uranium, thus it does not require235U certified standards.

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The complexes of molybdenum(VI) with trioctylamine (TOA, R3N) and trioctyl methylammonium chloride (TOMAC, R3R'NCl) were prepared by drying in vacuo the organic solutions for the extraction of molybdenum(VI) from hydrochloric acid solutions at low and higher acidities, respectively, by TOA and TOMAC in benzene. The resulting complexes were examined by thermal analysis (TG and DTA) in air and under the atmosphere of nitrogen, and their thermally decomposed products such as volatile matters and residues by gas chlomatography, X-ray diffraction study and infrared spectrophotometry. It was found that their complexes decompose thermally to MoO3 by cracking of alkyl groups combined with molybdenum(VI) ion. Accordingly the thermal decomposition process of those complexes is discussed and the probable structure of the complexes is proposed on the basis of the results obtained.

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Abstract  

The purpose of this work was the selective precipitation of Mo(VI) with a,a"-bipyridine and 1,10-phenanthroline. This precipitation, not reported in the literature, was used for the separation of molybdenum from the elements co-eluted from an alumina microspheres column. The alumina had been loaded using a nitric acid solution from the dissolution of a U-Al target. The emphasis was placed on the Mo(VI) separation from ruthenium, tellurium and iodine, all of them were eluted as a group of anionic complexes from the alumina column.

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Abstract  

Technetium-99m is the short-lived daughter product of the parent molybdenum-99, which is mainly produced by the fission of uranium-235. Management of radioactive waste is an integral part of fission 99Mo production and has high priority during the planning, design, construction and operational phase of a molybdenum-99 production facility. Within the licensing procedure the strategy of waste management, including the route for the spent targets and long lived fission products has to be described and approved by the responsible authorities. Waste will be generated as solids, liquids, and gases, and will include material in the low, intermediate and even highly radioactive categories. Initial treatment of waste streams is usually required at the production site, prior to short or long term storage. This technology is established and generally available in countries with an existing nuclear industry, such as Pakistan. In some instances storage facilities may need to be constructed. On site, treatment of gaseous waste will be carried out in the production facility while off-site treatment will be performed for solids and liquid radioactive waste.

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Abstract  

A rapid radioisotope induced energy-dispersive X-ray fluorescence procedure for the simultaneous determinations of Cobalt, Nickel and Molybdenum in hydrodesulfurization catalysts is presented. A109Cd (7 mCi) source is used as the excitation system coupled to a high resolution Si(Li) detector. A PDP-11/05 processor is employed as a multichannel analyzer and also to automatically control the complete system by means of a prewritten computer program. The relative standard deviations for the three determinations (CoO, NiO and MoO3) are less than 5% for 300 seconds of fluorescent time for a typical sample. Finally a comparison of results by different methods is given to check the accuracy since no standard reference materials are available for catalytic material.

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