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Abstract  

Experimental work was carried out in order to determine inorganic impurities in PVC latex by activation analysis. Arsenic and bromine were detected and quantitatively determined by means of two alternative methods: (a) comparison of the samples and As2O3 and KBr standard simultaneously irradiated with slow neutrons; (b) the same as (a), but considering only bromine and using standards made by adding and homogenizing known amounts of KBr in the PVC latex. All measurements were based on γ-spectrometry. The mean values given by method (a) are: arsenic (2.5±0.4)·10−4%, bromine (1.9±0.1)·10−3%. In method (b) the bromine found was (2.47±0.03)·10−3%.

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Abstract  

Well water analysis was carried out starting with liquid samples which have been evaporated to dryness. The salt deposit crust has ensured an enrichment in microelements which were approximately determined by emission spectroscopy. Once the order of magnitude was established, the exact measurements were carried out based on the following techniques: mass spectrometry, atomic absorption spectrophotometry, activation with slow neutrons, and γ-spectrometry. The results obtained are the average values of at least three methods employed. *** DIRECT SUPPORT *** A1353055 00005

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Abstract  

The chemical analysis of hydrated uranium tetrafluoride is described. This product was obtained in a wet process. Several methods were taken into account and applied to this product. In the case of uranium the following techniques were employed: isotope dilution with mass spectrometry, X-ray fluorescence, volumetric measurements, spectrophotometry, Volkovs's method, natural radioactivity measurements using the 185 keV235U peak and neuton activation analysis. In the case of fluoride determination, four methods gave good results. An explanation is given for a discrepancy appearing in one case. Free water in the product was determined in the classical way at 105 °C, with the Karl Fischer reagent and by thermogravimetric analysis. Hydration water was also estimated from thermogravimetric determinations in nitrogen to avoid product oxidation. Thus the formula UF42·2H2O was found. Other impurities were determined by emission spectroscopy, mass spectrometry, neutron activation and chemical analysis.

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Abstract  

Analysis of elements deposited on the surface layer of titanium anode was carried out with the aim of establishing their consumption during electrolysis process of natrium chloride solution. Mass spectrometry and neutron activation method associated with gamma-spectrometry were used and have permitted to find out the behaviour of different elements on titanium surface layers.

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Abstract  

Natural phosphates are used on large scale in the fertilizer industry. The usual process of the chemical attack is sulfuric (predominant) and nitric acids. The liquid phosphoric acid phase resulted contains dissolved valuable elements like: uranium and rare earths elements (REEs). Uranium and REEs are recovered in some technologies as valuable products. It is therefore important to know, uranium and REEs content in natural phosphates in view to decide on their recovery. In this paper determinations were carried out to find the uranium and REEs contents. The concentrations involved are low, therefore, it is difficult to find a classical reliable method without incurring important losses, i. e., errors. In this work uranium and REEs were determined by physical methods like: neutron activation analysis (NAA), emission spectroscopy, mass spark spectrometry and X-ray fluorescence. The results obtained were acceptable and intercomparison between various methods was carried out. It was found that most reliable results were given by mass spark spectrometry and activation analysis. The data resulted are in good agreement with uranium and REEs in the green cake (uranium tetrafluoride) and in the REEs concentrate obtained by solvent, extraction from phosphoric acid.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
F. Bunuş
,
V. Domocoş
,
R. Bulâceanu
,
P. Dumitrescu
, and
G. Popescu

Abstract  

In order to determine uranium from raw phosphoric acid solutions, resulted by the sulphuric acid attack of phosphate rocks and the strip solutions of the solvent extraction process for uranium recovery, two classes of analytical methods were established: one for low uranium content in phosphoric acid, and the other for higher uranium concentration in the same medium. The study was based on specific methods, therefore interference probability with other impurities in phosphoric acid medium is low. In the first class, X-ray fluorescence and spectrophotocolorimetric methods were used. X-ray fluorescence was applied on direct raw phosphoric acid solution and raffinate. The last one was associated with solvent extraction [di-(2-ethylhexyl) phosphate + triocylphosphine oxide] on the U(IV)-Arsenazo III complex in strip. The methods of the second class, were used for strip uranium concentrated solutions: X-ray fluorescence isotopic dilution and mass spectrometry, spectrophotocolorimetry and activation analysis associated with gamma-spectrometry. Here spectrophotocolorimetry involves two methods. The first one is based on the U(IV)-Arsenazo III complex and the other on direct U(IV)—phosphoric acid solutions measurements. A good agreement was obtained in each case for all comparative measurements involving various methods.

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