Separation of rhenium(vii) from molybdenum(vi) and many other elements by anion exchange

A method is described for the selective separation of μg and mg amounts of rhenium(VII) from molybdenum (VI) and many other metal ions by means of the strongly basic anion-exchange resin Dowex 1-X8. The separation is based on the preferential elution of molybdenum by a 90% (v/v) methanol-10% 6 M nitric acid mixture; rhenium and a few other elements are retained while molybdenum and most other metal ions including Fe(III), Ca, Mg, Mn, U, Cu, V, etc., are practically unadsorbed. After elution of the adsorbed rhenium with 70% (v/v) tetrahydrofuran-30% 9 M hydrochloric acid, the rhenium is determined spectrophotometrically by a modified thiocyanate method.     

Ion-exchange method for separation and concentration of platinum and palladium for analysis of environmental samples by inductively coupled plasma atomic emission spectrometry

An ion-exchange procedure is proposed for determination of Pt and Pd in environmental samples, using a Dowex 1-X10 anion-exchange resin. Pt and Pd were separated from the matrix elements in the sample by selective retention on the column as anionic chloro complexes and subsequent elution by circulated thiourea at 60 °C. The eluent, containing Pt and Pd was analyzed by inductively coupled plasma (ICP) atomic emission spectrometry (AES). Average recoveries of 98% and detection limit of 15 ng/g for both metals were achieved. Analysis of Pt and Pd concentrations in road dust, sampled from several sites in Germany was performed. The comparison of the obtained data with the concentrations of Pt and Pd in the same samples, determined by ICP-MS showed a very good agreement.     

Atomic-absorption determination of lead in geological materials

A method is described for the determination by atomic-absorption spectrophotometry of lead, tip to the milligram level, in samples of geological materials. After attack with perchloric-hydrofluoric acid mixture and the removal of perchlorate ion by precipitation as potassium perchlorate, lead is separated from matrix elements by means of anion-exchange in 2M hydrobromic acid on the strongly basic anion-exchange resin Dowex 1 x 8. Lead is adsorbed on the resin column while practically all other accompanying elements pass into the effluent. For the elution of lead 6(M) hydrochloric acid is used and after evaporation of the eluate lead is determined by atomic-absorption spectrophotometry. The method was tested by analysing numerous samples with contents ranging from a few ppm to milligram amounts of lead. In most cases very good agreement of results was obtained.     

Chemical analysis of manganese nodules : Part II. Determination of uranium and thorium after anion-exchange separation

A method is described for the determination of uranium and thorium in manganese nodules. After dissolution of the sample in a mixture of perchloric and hydrofluoric acids, uranium is adsorbed on the strongly basic anion-exchange resin Dowex 1 (chloride form) from 6 M hydrochloric acid. The effluent is evaporated and the residue is taken up in 7 M nitric acid—0.25 M oxalic acid; thorium is then isolated quantitatively by anion-exchange on Dowex 1 (nitrate form). Thorium is eluted with 6 M hydrochloric acid and determined spectrophotometrically by the arsenazo III method. Uranium is eluted from the resin in the chloride form with 1 M hydrochloric acid and then separated from iron, molybdenum and other co-eluted elements on a column of Dowex 1 (chloride form); the medium consists of 50% (v/v) tetrahydrofuran, 40% (v/v) methyl glycol and 10% (vv) 6 M hydrochloric acid. After removal of iron and molybdenum by washing the resin with a mixture of the same composition and with pure aqueous 1 M hydrochloric acid, the adsorbed uranium is eluted with 1 M hydrochloric acid and determined by fluorimetry. The method was used successfully for the determination of ppm-quantities of uranium and thorium in 60 samples of manganese nodules from the Pacific Ocean.     

A chromatographic determination of nitrate with amperometric detection at a copperized cadmium electrode

A copperized cadmium flow-through electrode is applied for cathodic detection of nitrate in the effluent stream of a liquid chromatograph. The nitrate is separated from dissolved oxygen in a small (10 cm) column of strong-base, anion-exchange resin (Dowex 1-X8) with 5 mM perchloric acid as the eluent. The effluent stream is buffered to pH 8 by mixing with a stream of buffer prior to detection. A large excess of chloride added to the sample dramatically improves the separation of nitrate from dissolved oxygen in the sample.     

Application of ion-exchange separations to determination of trace elements in natural waters-IX: simultaneous isolation and determination of uranium and thorium

A method is described for the determination of uranium and thorium in samples of natural waters. After acidification with citric acid the water sample is filtered and sodium citrate and ascorbic acid are added. The resulting solution of pH 3 is passed through a 4-g column of Dowex 1 x 8 (citrate form) on which both uranium and thorium are adsorbed as anionic citrate complexes. Thorium is eluted with 8M hydrochloric acid and separated from co-eluted substances by anion-exchange in 8M nitric acid medium on a separate 2-g column of the same resin in the nitrate form. After complete removal of iron by washing with a mixture consisting of IBMK, acetone and 1M hydrochloric acid (1:8:1 v v ) and treatment of the resin with 6M hydrochloric acid, the uranium is eluted from the 4-g column with 1M hydrochloric acid. In the eluate thorium is determined spectrophotometrically (arsenazo III method) while fluorimetry is employed for the assay of uranium. The procedure was used for the determination of uranium and thorium in numerous water samples collected in Austria, including samples of mineral-waters. The results indicate that a simple relationship exists between the uranium and thorium contents of waters which makes it possible to calculate the approximate thorium content of a sample on the basis of its uranium concentration and vice versa.     

Separation of bismuth from lead, copper and other elements by means of anion exchange

The anion-exchange behaviour of bismuth and various other elements has been investigated in media consisting of methyl glycol and nitric acid. Through the determination of the distribution coefficients in such mixtures, a method for the anion-exchange separation of bismuth from many metal ions has been developed. A mixture of 90% methyl glycol and 10% 5M nitric acid is a suitable medium for this separation on the strongly-basic anion exchanger Dowex 1, X8. Only bismuth, thorium and lanthanum are strongly retained on the resin in these conditions. All other elements investigated, such as lead, copper, iron, etc., are either only weakly adsorbed or are not absorbed. By means of this ion-exchange procedure, a series of analyses of copper-base alloys for bismuth has been carried out. The results show that this method can be used successfully for the quantitative isolation of bismuth from such materials. The final determination of bismuth in the eluates is performed by complexometric titration.     

Anion-exchange separation and spectrophotometric determination of thorium in geological samples

To determine thorium in geological samples it is first separated from all matrix elements by means of anion-exchange. After elution thorium is determined spectrophotometrically by using thoronol or arsenazo III. The suitability of the method for the determination of both trace and larger amounts of thorium was tested by analysing numerous geochemical standard samples with thorium contents in the range of 1-1000 ppm. In all cases very good agreement was obtained.     

Anion-exchange separation of cadmium in organic solvent-nitric acid media

The anion-exchange separation of cadmium from zinc and aluminium in organic solvent-nitric acid mixtures was studied. The distribution coefficients of the 3 elements in various 90% organic solvcnt-10% 5 N nitric acid media were determined for Dowex I-X8 resin. A 90% ethanol-10% 5 N nitric acid medium was most satisfactory for the quantitative separation of cadmium from zinc and aluminium. The method was applied to the analysis of some copper and aluminium base alloys. Methyl glycol or acetic acid could be used instead of ethanol. Both cadmium and zinc were strongly adsorbed from a 90% propionc acid-10% 5 N nitric acid medium; separation was then effected by gradient elution.     

Anion exchange studies of indium(III) in malonate and ascorbate solutions separation from mixtures

Summary Systematic studies are presented on the anion-exchange behaviour of indium on Dowex 21K in malonic acid and ascorbic acid solutions. Hydrochloric, sulphuric, nitric and perchloric acids, also sodium and ammonium nitrate at different concentrations were tested as eluants in the two systems. Their efficiency was evaluated in terms of elution constants. Methods have been developed for the separation of indium from several elements in malonate as well as ascorbate media with the technique of selective sorption, selective elution or by gradient elution.     

Anion exchange separation of uranium, thorium and bismuth

Summary A method for the anion exchange separation of uranium, thorium and bismuth is described, using the strongly basic anion exchanger Dowex 1 X8. These three elements are simultaneously adsorbed on the resin (nitrate form) from a solution consisting of 96% n propanol and 4% 5 n nitric acid. The separation of thorium and bismuth from uranium is effected by washing the column with a mixture consisting of 80% methanol and 20% 5n nitric acid (elution of uranium). To separate thorium from bismuth the resin is then treated with a solution consisting of 80% methanol and 20% 6n hydrochloric acid whereby the thorium is eluted. Finally the bismuth is removed by washing the column with 1 n nitric acid. The experimental conditions for this separation scheme have been selected after the determination of the distribution coefficients of uranium, thorium, and bismuth in different mixtures of aliphatic alcohols with nitric and hydrochloric acid.

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Zusammenfassung Zur Trennung von Uran, Thorium und Wismut wird der stark basische Anionenaustauscher Dowex 1X8 verwendet. Aus einem Lösungsmittelgemisch von 96% n-Propanol und 4% 5n Salpetersäure werden die drei Elemente zusammen an dem Austauscher (Nitratform) adsorbiert. Mit einer Mischung von 80% Methanol und 20% 5n Salpetersäure wird sodann das Uran eluiert. Thorium wird mit einem Gemisch von 80% Methanol und 20% 6n Salzsäure ausgewaschen und schließlich wird mit 1 n Salpetersäure das Wismut von der Säule entfernt. Die Verteilungskoeffizienten der drei Metalle wurden in verschiedenen Gemischen von aliphatischen Alkoholen und Salz- sowie Salpetersäure bestimmt.

     

Photon activation analysis of trace metals in biological materials via collection of metal tropolone-5-sulfonate complexes onto anion-exchange resin

Tropolone-5-sulfonic acid was used to separate and collect trace elements as their complexes onto an anion-exchange resin in photon-activation of biological materials. Retention behaviour of the anionic complexes of Cr, Mn, Fe, Co, Ni, Cu, Zn, and Pb on Dowex 1-X8 resin was examined with respect to pH, amount of resin, concentration of the ligand, and coexisting salt anions, using radioisotope tracers. Under optimum conditions, Cr, Mn, Co, Ni, Zn and Pb were collected from the irradiated samples of NBS-SRM Orchard Leaves, NBS-SRM Spinach, green tea and black tea on the marcket. The analytical results agreed with certified values and the reproducibility was good.     

Mutual Separation of Rare Earths in Monazite with Cation Exchange Elution Chromatography

Mutual separation of the individual rare earth elements (exception of cerium) in monazite from different districts was investigated by cation exchange elution method. Strong acid type cation exchange resin, Bio-Rad AG 50 Wx8 and eluting solution of a α-hydroxyisobutyric acid (α-HIBA) were used. Radioactivity tagged Eu-152, 154 or Tb-160 were used as radio active indicator for determination of the distribution coefficients by batch method or for the study of column elution conditions. By gradiently increase of the pH values from 3 to 5 in 0.3 M α-HIBA eluting solution, complete mutual separation of individual rare earth elements, exception of Dy and Y, were obtained. Dy and Y could not be separated by this scheme of separation and their elution zones were overlapped. Rare earth mixture samples of monazite from different districts were separated with this scheme and these results were compared. From this comparison followings were noticed; 1. Compositions of rare earth elements in monazite from different districts are evidently not alike. 2. Samples from Brazil and Southwestern Coast of Taiwan are much more alike in their compositions but not for those from Australia and Outskirt Island. 3. Sample from Outskirt Island has higher in contents of heavier rare earths and also Nd was higher than La.     

Determination of vanadium and molybdenum by atomic-absorption spectrophotometry

A method is described for the determination by atomic-absorption spectrophotometry of vanadium and molybdenum, up to the milligram level, in samples of yellow cake, uranium-bearing minerals and geochemical standards. After attack with acids these two elements are separated from each other and from matrix elements by means of anion-exchange in 6M hydrochloric acid on the strongly basic anion-exchange resin Dowex 1, X8 (chloride form). Vanadium is unadsorbed and passes into the effluent while molybdenum is adsorbed on the resin. For the elution of molybdenum a mixed aqueous-organic solvent system consisting of methanol and 6M hydrochloric acid (9: 1 v/v) is used. After evaporation of the 6M hydrochloric acid effluent and of the mixed aqueous-organic eluate vanadium and molybdenum are determined by atomic-absorption spectrophotometry. The method was tested by analysing numerous samples with contents ranging from a few ppm to milligram amounts of vanadium and molybdenum. For comparison, the concentrations of these two elements were determined in a large number of samples by spectrophotometric and titrimetric procedures. In all cases very good agreement of results was obtained.     

Anion-exchange isolation of rare-earth elements from apatite minerals in methanol-nitric acid medium

Batch distribution coefficients, K_d, of rare-earth elements (REE) and other elements were determined radiochemically for a strongly basic nitrate anionexchange resin Dowex 1-X8 100–200 mesh, in nitric acid-methanol media of varying composition. This method was developed for the separate recovery of REE from apatite minerals. Calcium and other common elements of the apatite are eluted by a 5% (v/v) 7 M nitric acid-95% methanol mixture, while the REE are retained. The REE are recovered and separated into two fractions; the heavier REE by elution with a 45% nitric acid-55% methanol mixture, and a very clean fraction of La, Ce, Pr, Nd by elution with water.     

Sorption of uranium and thorium from sulphuric acid using TVEX-PHOR resin

Summary Solid-liquid extraction has been used to study the uptake of uranium(VI) and thorium(IV) from sulphuric acid using a TVEX-PHOR resin. The experimental results were found to fit the BET isotherm and show a higher affinity of the TVEX-PHOR resin towards the extraction of uranium than thorium under similar experimental conditions. The best separation of uranium from thorium is obtained from 3M sulphuric acid at V/m ratio of 20 ml/g. Elution of loaded uranium and thorium was carried out with 1M sodium carbonate and 0.075M sulphuric acid, respectively. After the elution of both elements, the regenerated resin could be reused with high efficiency.     

Anion-exchange behaviour of the platinum metals and gold in hydrochloric acid-organic solvent media

The anion-exchange characteristics of the platinum metals and gold in hydrochloric acid media are described. The distribution coefficients of these elements were measured on the strongly basic anion-exchange resin Dowex 1 x 8 in mixtures of hydrochloric acid with water and several organic solvents, i.e., dimethylformamide, acetone, tetrahydrofuran, dioxan, methanol, acetic acid and pyndine. Based on these data the conditions most suitable for quantitative separation are indicated and discussed.     

Separation of arsenic(III) and arsenic(V) in ground waters by ion-exchange

The predominant species of arsenic in ground water are probably arsenite and arsenate. These can be separated with a strong anion-exchange resin (Dowex 1 x 8; 100-200 mesh, acetate form) in a 10 cm x 7 mm column. Samples are filtered and acidified with concentrated hydrochloric acid (1 ml per 100 ml of sample) at the sample site. Five ml of the acidified sample are used for the separation. At this acidity, As(III) passes through the acetate-form resin, and As(V) is retained. As(V) is eluted by passage of 0.12M hydrochloric acid through the column (resulting in conversion of the resin back into the chloride form). Samples are collected in 5-ml portions up to a total of 20 ml. The arsenic concentration in each portion is determined by graphite-furnace atomic-absorption spectrophotometry. The first two fractions give the As(III) concentration and the last two the As(V) concentration. The detection limit for the concentration of each species is 1 mug l .     

On-line preconcentration of palladium(II) using a microcolumn packed with a chelating resin, and its subsequent determination by graphite furnace atomic absorption spectrometry

Palladium(II) is preconcentrated on a chelating resin microcolumn [1,5-Bis(2-pyridyl)-3-sulphophenyl methylene thiocarbonohydrazide immobilized on an anion-exchange resin (Dowex 1 X8-200)] placed in the autosampler arm, followed by the elution of the Pd-chelate with nitric acid and subsequent determination of Pd from the eluate by graphite furnace atomic absorption spectrometry. The method was applied to the recovery of Pd(II) ions from different samples.     

Quantitative separation of Al, Ga, In, and Tl by cation exchange chromatography in hydrochloric acid-acetone

Up to 4 mmole (1 mmole each) of tervalent Al, Ga, In and Tl are separated from each other on a 60-ml column of AG50W-X8 resin of 200-400 mesh particle size by cation-exchange chromatography in hydrochloric acid-acetone mixtures. Separations are very sharp and without tailing. Recoveries for amounts from 1-100 mg average 100.0 +/- 0.1 % for the analysis of synthetic mixtures. An anion-exchange method is described for the separation of gallium from the hydrochloric acid-acetone eluate. Relevant cation-exchange distribution coefficients, anion-exchange coefficients for gallium in hydrochloric acid-acetone, an elution curve for all four elements and results of quantitative separations of synthetic mixtures are presented.