Trace Amounts Of Uranium Research Articles

Flotation of Uranium from Seawater with Phosphate Esters of C-Undecylcalix[4]resorcinarene

Abstract Table-type chelating surfactants ([4]ArmX-R12, mX means the number of phosphates (P), carboxylic acid (Ac), and hydroxamic acid (Hx), respectively) have been derived from the calix[4]resorcinarene bearing tetradodecyl side chains ([4]Ar-R12), and applied to a collector of uranium flotation. The surface tension of the aqueous solution was 35 mN m−1 for [4]Ar5.6P-R6 (Rn means the alkyl chain length), 52 mN m−1 for [4]Ar5.9P-R12, 42 mN m−1 for [4]Ar8.0Ac-R12, and 48 mN m−1 for [4]Ar5.1Hx-R12. They formed UO2 complexes and floated the UO22+ from an aqueous solution by air-bubbling. Furthermore, [4]Ar5.9P-R12 and [4]Ar6.3P-R12 had competence to float the uranium from seawater. A trace amount of uranium in 450 cm3 of seawater was floated at 68—94% using 1—10 mg of [4]Ar5.9P-R12 or [4]Ar6.3P-R12. On the other hand, [4]Ar5.1Hx-R12 and [4]Ar8.0Ac-R12 brought about lower floatabilities. [4]ArmP-R12 could be recycled several times by dissolving the scum (uranium complex) in 5 mol dm−3 H2SO4.

A sensitive spectrophotometric method for the determination of trace amounts of uranium (VI) using o-hydroxypropiophenone isonicotinoyl hydrazone

The reaction between uranium (VI) and o-hydroxypropiophenone isonicotinoyl hydrazone (OHPINH) has been investigated in HCl-sodium acetate buffers and a highly sensitive and simple procedure for the determination of uranium (VI) is suggested. The yellow colored complex showed maximum absorption at 380 nm in buffer solutions of pH 3. Beer's law is obeyed in the range of 0.47–17 μg ml−1. The molar absorptivity and Sandell sensitivity are found to be 1.15×104 dm3 mol−1 cm−1 and 0.02 μg cm−2, respectively. The composition of the complex is found to be 1∶1 between metal and reagent.

A sensitive spectrophotometric method for the determination of trace amounts of uranium(VI) using 2-hydroxy-1-naphthaldehyde isonicotinoyl hydrazone

The reaction between uranium(VI) and 2-hydroxy-1-naphthaldehyde isonicotinoyl hydrazone (2HNAINH) has been investigated in HCl-sodium acetate buffers and a highly sensitive and simple procedure for the determination of uranium(VI) is suggested. The orange red colored complex showed maximum absorption at 430 nm in buffer solutions of pH 3. Beer's law is obeyed in the range of 0.2 to 33 μg ml−1. The molar absorptivity and Sandell's sensitivity are found to be 9.6×103 mol·l−1 and 0.025 g cm−2, respectively. The composition of the complex between metal and reagent is found to be 1∶1. The effect of diverse ions is also studied and the method is successfully applied for the determination of uranium in synthetic mixtures.

Etched topography in nuclear track detectors and effect on quantitation related to sample composition

Abstract When using the nuclear track technique for multi-element detection and spatial mapping, the presence of moderate to high concentrations of boron or lithium results in a large number of (n,α) reactions when using the high thermal neutron fluences required to map trace amounts of uranium. When chemically etched, tracks generated by a large number of alpha particles cannot be spatially resolved, and are manifested instead by large-scale depressions in the detector surface. High Li and B concentration samples have the most pronounced topographic development in both CR-39 and CN detectors. Samples with low concentrations of Li and B or high concentrations of Gd, Sm or Eu developed moderate depressions. These depressions can affect uranium quantitation, but simultaneously, they provide useful information about the sample. This paper is a preliminary study of observations of etched bulk depressions, variations in track revelation time, and the mapping of samples containing elements with high thermal neutron absorption cross sections such as gadolinium.

Application of laser-induced fluorescence for determination of trace uranium, europium and samarium

Trace amounts of uranium, europium and samarium can be determined by means of laser-induced fluorescence. The fluorescence emission and excitation spectra were observed by adding fluorescence enhancing reagents. The fluorescence lifetimes of these elements were also measured. The intensities of emission were found to be linear with respect to the concentration of the element over a wide range. The detection limits for U(VI), Eu(III), and Sm(III) were established as 0.05, 0.1, and 10 ng/ml, respectively. The study suggested that this is a suitable technique for the trace determination of uranium and rare earth elements.

Extraction and spectrophotometric determination of uranium in phosphate fertilizers

An extraction and spectrophotometric method for determination of trace amounts of uranium in phosphate fertilizers is described. It is based on the extraction of uranium with trioctylphosphine oxide in benzene and the spectrophotometric determination of uranium with Arsenazo III in buffer-alcoholic medium. The maximum absorbance occurs at 655 nm with a molar absorptivity of 1.2·104 l·mol−1·cm−1. Beer's law is obeyed over the range 0.6–15.0 μg·ml−1 of uranium(VI). The proposed method has been applied successfully to the analysis of phosphate fertilizers with phosphate concentrations of 45% P2O5.

A method to enhance porosity of micro-particles

The nuclear track technique (NTT) is used to enhance the porosity of silica micro-particles. The enhanced porosity is a result of the formation of surface and interior pores or tracks in the silica by the action of external and internal fission fragments. The fission tracks produced at the surface and within the interior of the micro-particles are a result of coating the particles with trace quantitities of uranium, instead of having trace quantities of uranium incorporated within the silica matrix.

CSA Continuous Countercurrent Ion Exchange (CCIX) Technology

Abstract The CSA-CCIX concept started at ORNL in 1951. It has been adapted to a wide variety of applications worldwide, in water and waste water treatment, fertilizers, hydrometallurgy, and general chemical processing. Unique features and how it works are described. Two extreme applications are described in detail. One is for the extraction of trace amounts of uranium from a copper leach, at 37.85m3/min (10,000 gpm) where very high throughput rates are emphasized. The other is for Acid Retardation, where a strong acid waste is purified and recovered. The feed processing rate here is much lower than the resin rate.

Highly accurate determination of trace amounts of uranium in standard reference materials by spectrophotometry with chlorophosphonazo III after complete separation by anion and cation exchange chromatography

A method is described for the highly accurate determination of trace amounts of uranium in standard reference materials. The uranium is separated from the bulk elements by anion-exchange chromatography, eluting most elements with 6 M hydrochloric acid and iron(III) with 0.5 M hydrochloric acid in 90% acetone. After elution of uranium with 0.1 M hydrochloric acid, residual traces of other elements are separated by a very selective cation-exchange procedure using a 3 g resin column. Finally the uranium is determined in the hexavalent state by spectrophotometry at 672 nm of its complex with chlorophosphonazo III at pH 1.1±0.2 in the presence of DTPA. Results are very accurate and precise even on a semi-routine basis. Relevant elution curves and results are presented for recovery tests and for the analysis of the 10 South African UREM standard materials.

Polarographic determination of trace amounts of uranium ? a review

A review of methods for the polarographic determination of microgram amounts of uranium in artificial solutions and in natural samples with special reference to marine materials is given. A mechanism is suggested for the formation of catalytic uranium waves, depending on the composition of the supporting electrolyte.

Determination of uranium in sea water by preconcentration on Chelex 100 and neutron activation

Trace amount of uranium in sea water was preconcentrated on Chelex 100 chelating resin. The resin was directly applied as a support for irradiation.239U was selectively and quantitatively recovered from the irradiated resin by elution, using 1.0M sodium carbonate solution as eluant. γ-Ray spectrum was measured with a Ge(Li) detector.

Method to avoid losses of uranium at the interface between different eluting agents during anion exchange chromatography

It is shown that substantial amounts of uranium can be lost at the interface between eluting agents when two different groups of interfering elements are eluted successively from a single anion exchange column with sulfuric acid or ammonium sulfate followed by hydrochloric acid of fairly high concentration. These losses are small or negligible when only small or trace amounts of uranium are present. For large amounts of uranium they can be as large as about 10 percent. The cause was found to be a wave of high concentration of sulfuric acid which precedes the hydrochloric acid. In this wave the distribution coefficients of uranium are low and the uranium is mobilized on the column. By inserting a buffer of 30 mL of 2 M hydrochloric acid containing 75 percent methanol between the two eluting agents, the losses can be avoided. Relevant elution curves and distribution coefficients are presented together with analysis results showing percentage losses for various amounts of uranium.

Precise and rapid determination of trace amounts of uranium in inorganic samples by neutron activation and TBP extraction

Neutron activation analysis is one of the very few annlyticnl techniques that can be used for rcliuble determination of uranium ut the p.p.lOy concentration level. A very sensitive version is the one based on measurement of 23.5-min 239U originating from the (n, 11) reaction in 2JEU. provided that u selective and rapid separation procedure giving high chemical yield is avuilable. Such a procedure might be based on extraction with tri-n-butyl phosphate (TBP) from nitric acid media, which has been extensively used in nuclear fuel reprocessing work. It was recently shown’ that urunium could be determined in fresh water by a singleextruction into TBP from ( 1 -II) nitric acid. When the need arose for uranium determination in high-purity yttrium oxide. it was decided to study the applicability of the TBP-HN03 system on a wider range of samples. Distribution coefficients for more than 70 elements in the T&P-HN03 system ha& been given2. According to these data extraction from 5 M nitric acid into 25% TBP seemed to be the optimal choice. In 100% TBP. it would be necessary to go down to l-2 M nitric acid in order to remove efficiently a number of elements including yttrium and the heavy rare earths, and at those low concentrations the uranium yield would probably be unsatisfactory. In the case of 25x, TBP, only Au. Th und Np would be extracted along with uranium from 8 5 M nitric acid solution to any significant degree. This would allow the determination of thorium uiu 22.4-min 233Th simultaneously with uranium.

A fluorimetric attachment for an atomic-absorption spectrophotometer

A simple reflectance fluorimeter has been developed for the determination of trace amounts of uranium by the sodium fluoride fusion method. The unit incorporates the electronic system of the Techtron AA3 atomic-absorption spectrophotometer. A method for the preparation of the fusion beads is also described.

Spectrophotometric determination of uranium with 1-(2-pyridylazo)-2-naphthol

1-(2-Pyridylazo)-2-naphthol (PAN) rcacts with uranium to form a deep red precipitate in ammoniacal solutions, this can be extracted with chloroform if sodium chloride or sulfate is added and it has a maximum absorption at 560 mμ The color is stable and follows Beer's law. Trace amounts of uranium may be determined in the presence of many metals without prior separation if strong complexing agents, such) as EDTA or cyanide, are added

Determination of Traces of Uranium with 1-(2-Pyridylazo)-2-naphthol

1-(2-Pyridylazo)-2-naphthol reacts with many polyvalent metals, forming intensely colored complexes. However, in the presence of strong complexing agents, such as (ethylenedinitrilo)tetraacetic acid and cyanide, it reacts only with uranium to form a deep red finely divided precipitate in ammoniacal solutions. The naphthol complex can be exracted by o-dichlorobenzene and has its maximum absorption at 570 m mu . The color is stable and follows Beer's law over the range of 0.1 to 5 a 10/sup -4/ mmole of uranium in 10 nd of the solvent. The molar absorptivity of 1-(2-pyridylazo)-2-naphthol is 23,000; therefore, it may be the most sensitive color reagent for uranium. Trace amounts of uranium may be determined in the presence of many metals without prior separation. (auth)

Uranium deposits in western North Dakota and eastern Mountana

Exploration in the lignite basin in western North Dakota and eastern Montana followed discovery of trace amounts of uranium in Paleocene lignites. Proved and probable reserves of more than 200,000 tons of lignite containing more than 0.10 percent uranium oxide have been developed.Bedded and lenticular deposits in both lignite and sandstone beds were concentrated by circulating ground water.Most of the uranium is in complex carbon-uranium compounds. Metatyuyamunite and autunite are common secondary minerals. Ore deposition is controlled by carrier bed permeability, by host-rock petrography, and by structure.The milling of lignite to produce a metal is a difficult process to perfect. Progress in milling is necessary before this potential uranium reserve can become an economic ore.