Radiotracer analysis of the physico-chemical state of trace elements in aqueous solutions

Podhájecký, P.; Beneš, P.; Gosman, A.

doi:10.1007/bf02520502

Cited by 4 publications

(3 citation statements)

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“…The decrease in the apparent diffusion coefficient at pH 3 -5, which is similar to the decrease observed by KEPÄK and KfclVA [13], reflects the formation of cerium pseudocolloids. In separate experiments with carrier-free 144 Ce we found that an addition of indifferent electrolyte (NaCl) to the studied solution enhances the apparent diffusion coefficient of cerium [28]. This provides an additional support to the pseudocolloidal concept, because it is known that electrolyte can suppress adsorption of trace cations on colloidal impurities.…”

Section: Resultsmentioning

confidence: 49%

“…The diffusion coefficients found at higher pH values can not be considered as real diffusion coefficients since two or more forms of cerium are present in the solution and the diffusion coefficient obtained under such conditions does not represent a mean diffusion coefficient [28]. The decrease in the apparent diffusion coefficient at pH 3 -5, which is similar to the decrease observed by KEPÄK and KfclVA [13], reflects the formation of cerium pseudocolloids.…”

Section: Resultsmentioning

confidence: 75%

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Radiochemical Study of the Physicochemical State of Trace Cerium in Aqueous Solutions

1979

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The physicochemical state of trace cerium (III) in aqueous chloride solutions was studied using centrifugation, free-liquid electrophoresis and continuous capillary diffusion methods and 141 Ce. It has been found that cerium is present predominantly as Ce 3 + cations in 0.1 -0.001 Μ solutions of hydrochloric acid. Colloidal forms of carrier-free 141 Ce exist in the solutions of lower acidity (pH > 3). They are formed by adsorption of cerium ions'on colloidal impurities in the solutions or by coprecipitation of cerium with colloidal ferric hydroxide, present in the solutions as an impurity. Tervalent cerium does not undergo a hydrolysis at pH < 5.Knowledge of the physicochemical state of trace elements in aqueous solutions is of considerable importance for prediction and interpretation of behaviour of trace elements in many physicochemical and biochemical processes [1,2]. The physicochemical state of trace cerium in aqueous solutions is not sufficiently known. Particularly the hydrolysis and the colloidal behaviour of tervalent cerium are subject to controversies among various authors. Thus for instance STEPANOV and SHVEDOV [3], SHALINEC [4] and PUSTOVALOV et al. [5] claim that hydrolysis of trace cerium is significant already at pH > 2-3, whereas it should be negligible (less than 10%) at pH < 8 according to the hydrolytic constants published by other authors [6,7], Formation of colloidal forms of trace cerium(III) in aqueous solutions has been reported by several authors [8 -16]. However, the authors largely disagree as to the nature and the region of existence of the colloids. This is mainly due to different conditions and methods used for the studies and sometimes also due to inadequate interpretation of the data obtained. It seemed therefore useful to reinvestigate these problems using well defined conditions and combining several methods of study. Electrophoresis, centrifugation and capillary diffusion were used to elucidate the physicochemical state of trace cerium in aqueous solutions labelled with carrier-free 141 Ce. Experimental Reagents and solution preparationTriply distilled water and p. a. reagents were used throughout. All stock solutions were prepared by dissolving or diluting exact amounts of chemicals and were stored in clean polyethylene bottles. Stock solutions of sodium hydroxide were prepared from carbonate-free, 50% solution of NaOH. Preparations of 141 Ce (carrier-free, CeCl 3 in 1 Μ HCl), supplied by Zentralinstitut für Kernforschung, Rossendorf near Dresden, were used as radiotracers. They were suitably diluted with 0.01 Μ HCl. For some experiments, a standard inactive solution of CeCl 3 was added.The experimental solutions were prepared by gradually mixing the stock solutions of radiocerium, 0.01 Μ HCl and 0.01 Μ or 0.1 Μ NaOH so as to obtain the desired pH. All the mixing was carried out at room temperature in a glove box to avoid an uncontrolled contamination of the solutions with dust. Unless stated otherwise, the ionic strength of the solutions was 0.01 (HCl + NaCl + NaOH). The solu...

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Section: Resultsmentioning

confidence: 49%

Section: Resultsmentioning

confidence: 75%

Radiochemical Study of the Physicochemical State of Trace Cerium in Aqueous Solutions

1979

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“…Some of the techniques ensure that disturbances of chemical equilibrium are avoided, kept at minimum or do not affect speciation analysis. Particularly suitable for this purpose are various spectroscopic methods (e.g., LIPAS, etc., see above), free-liquid electrophoresis [7,143], diffusion [144], and special methods of solvent extraction [145]. Relatively rapid physical separation methods like centrifugation, filtration and ultra-filtration [36,146] in small-volume arrangements do often not significantly disturb the equilibrium, either.…”

Section: Model Experiments For Aqueous Speciationmentioning

confidence: 99%

Speciation of Radionuclides in the Environment

Gunten

Beneš

1995

Radiochimica Acta

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Methods for the determination of the speciation of radionuclides in aerosols, in aquatic solutions, in sediments, soils and rocks are reviewed. At present, most of the results about speciation are deduced from model calculations, model experiments, and separation of species (forms) of radionuclides, e.g., by sequential extraction procedures. Methods of direct determination of speciation of radionuclides (e.g., by laser induced spectroscopy) are in general not yet sensitive enough for a measurement of the very low concentrations of radionuclides in the environment. The methodological part of this paper is followed by a review of the very abundant literature about speciation of important radionuclides in the environment, i.e., in the atmosphere, hydrosphere and lithosphère. The review does not include the biosphere. Literature up to spring 1993 is included (with a few more recent additions).

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Radiotracer Methods

Das¹

2000

Encyclopedia of Analytical Chemistry

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Small amounts of radionuclides of suitable half‐life can be used to observe the kinetics of mass transport and isotopic exchange in the equilibrium distribution of a (micro‐)component between coexistent phases. Quantitative assay of radioactivity is sensitive, precise and accurate and usually performed instrumentally. Though handling of radionuclides is restricted to authorized laboratories only, the combination of its potential and simplicity makes the radiotracer method an indispensable part of modern analytical chemistry.

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Radiotracer analysis of the physico-chemical state of trace elements in aqueous solutions

Cited by 4 publications

References 10 publications

Radiochemical Study of the Physicochemical State of Trace Cerium in Aqueous Solutions

Radiochemical Study of the Physicochemical State of Trace Cerium in Aqueous Solutions

Speciation of Radionuclides in the Environment

Radiotracer Methods

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