Determination of uranium in minerals and rocks

A method is described for the determination of uranium in minerals and rocks by spectrophotometry and fluorimetry. After treatment of the sample with hydrochloric acid, uranium is separated from matrix elements by adsorption on a column of the strongly basic anion-exchange resin Dowex 1 x 8 from an organic solvent system consisting of IBMK, tetrahydrofuran and 12M hydrochloric acid (1:8:1 v v ). Following removal of iron, molybdenum and co-adsorbed elements by washing first with the organic solvent system and then with 6M hydrochloric acid, the uranium is eluted with 1M hydrochloric acid. In the eluate, uranium is determined by means of the spectrophotometric arsenazo III method or fluorimetrically. The suitability of the method for the determination of both trace and larger amounts of uranium was tested by analysing numerous geochemical reference samples with uranium contents in the range 10(-1)-10(4) ppm. In practically all cases very good agreement of results was obtained.     

Anion-exchange separation and spectrophotometric determination of vanadium in silicate rocks

A combined anion-exchange-spectrophotometric method has been developed for the determination of vanadium in silicate rocks. A rock sample weighing about 0.1 g is decomposed with a mixture of sulphuric and hydrofluoric acids and after removal of HF the residue is taken up with dilute sulphuric acid. This solution is adjusted to be 0.05M in sulphuric acid and contain 0.3% hydrogen peroxide, and is passed through a column of Amberlite CG 400 (sulphate form). The sorbed vanadium is eluted with 30 ml of 1M hydrochloric acid. The effluent is evaporated to dryness, made 0.1M in hydrochloric acid and 3% in hydrogen peroxide content, and passed through a column of Amberlite CG 400 (chloride form) to get rid of accompanying thorium and zirconium. Vanadium is stripped by elution with 20 ml of 1M hydrochloric acid and subsequently determined spectrophotometrically with 4-(2-pyridylazo)resorcinol. The detection limit is 0.4 ppm.     

Radiochemical purification of microgram and sub-microgram amounts of beryllium

A method is presented for the separation and radiochemical purification of microgram and tracer amounts of beryllium from solutions. It is a four-stage ion-exchange procedure consisting of (1) selective adsorption of the beryllium onto NaDAP resin and its elution with ammonium fluoride, (2) adsorption of the fluoroberyllate complex onto an anion-exchange column and elution of the beryllium with hydrochloric acid, (3) adsorption and selective elution of the beryllium on a cation-exchange column and (4) a pass through an anion-exchange column in concentrated hydrochloric acid. The method is quantitative and requires no carrier. Decontamination factors from most radionuclides tested were greater than 10,000. The method can be used to determine beryllium-10 in environmental materials.     

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.     

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.     

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 .     

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.     

Methods for the separation of rhenium, osmium and molybdenum applicable to isotope geochemistry

Effective methods are described for the chemical separation of rhenium, osmium and molybdenum. The methods are based on distillation and anion-exchange chromatography, and have been the basis for rhenium-osmium isotope studies of ore deposits and meteorites. Successful anion-exchange separation of osmium requires both recognition and careful control of the osmium species in solution; thus, distillation of osmium tetroxide from a mixture of sulfuric acid and hydrogen peroxide is preferred to anion-exchange. Distribution coefficients measured for perrhenate in sulfuric acid media are sufficiently high (K(d) > 500) for rhenium to be directly loaded onto an ion-exchange column from a distillation residue and subsequently eluted with nitric acid. Polymerization of molybdenum species during elution is prevented by use of a solution that is 1M in hydrochloric acid and 1M in sodium chloride.     

Anion-exchange separation of plutonium in hydrochloric-hydrobromic acid media

Plutonium can be rapidly and selectively separated from the elements that interfere in its radiochemical determination, by the use of hydrobromic acid in a hydrohalic acid anion-exchange separation procedure. Plutonium(IV) and (VI) are adsorbed onto the resin column from 9M hydrochloric acid, interfering elements such as americium and thorium are washed from the column with 9M hydrochloric acid, and the plutonium is reduced to plutoniurn(III) and washed from the column with 11M hydrobromic acid. Interfering elements such as uranium and neptunium, which are adsorbed onto the column from 9M hydrochloric acid, are retained there during the hydrochloric and hydrobromic acid washes. This system would also appear to provide the means for effectively separating plutonium from those elements that commonly interfere in such chemical methods of analysis as redox titration.     

Separation of95Zr and95Nb from each other and from other fission products by adsorption and desorption on silica gel using hydrochloric acid solutions

The silica gel adsorption behaviour of zirconium, niobium, ruthenium and cerium in hydrochloric acid has been investigated by batch and column techniques. A satisfactory radiochemical separation of zirconium and niobium from each other and from other fission products has been achieved by a two column technique. The recommended procedure consists of sorption of all the nuclides on a primary silica gel column. Fifteen per cent of⁹⁵Nb, all of the zirconium and all of the other fission products are eluted first by washing with 5.5 M HCl. A second elution with concentrated hydrochloric acid then recovers the⁹⁵Nb (free from other products). The solution from the first elution after evaporation to 1 ml is then passed through another silica gel column and successively washed with 0.5M HCl, 5.5M HCl and concentrated HCl to obtain three fractions—other fission products—⁹⁵Zr free from other products—⁹⁵Nb free from other products, respectively.     

Chemical analysis of manganese nodules: Part III. Determination of Thallium,Molybdenum and Vanadium after Anion-Exchange Separation

A method is described for the determination of thallium, molybdenum and vanadium in manganese nodules. After dissolution of the sample in a mixture of perchloric and hydrofluoric acids, thallium and molybdenum are adsorbed on the strongly basic anion-exchange resin Dowex 1 (chloride form) from 6 M hydrochloric acid containing bromine. Molybdenum is eluted with 2 M perchloric acid-1 M hydrochloric acid and determined by a.a.s. with a nitrous oxide—acetylene flame. Thallium is eluted with an aqueous solution of sulphur dioxide and, after evaporation of the eluate, this element is determined by a.a.s. with an air—acetylene flame. The same method is used for the assay of vanadium in the 6 M hydrochloric acid effluent. The method was used successfully for the determination of thallium, molybdenum and vanadium at the ppm level in numerous samples of nodules from the Pacific Ocean and Lake Michigan.     

Highly selective ion chromatographic determination of ammonium ions in waters with a suppressor as postcolumn reactor

A highly selective ion chromatographic method for the determination of ammonium ions using an anion-exchange separation column with a bipolar ion exchanger was developed. The method is based on the reaction in a suppressor column between ammonium ions and nitrous acid formed from the eluent components followed by the negative conductimetric signal. The determination of more than 0.1 ppm of NH₄⁺ in water is possible in the presence of 100-fold amounts of alkali metals and inorganic anions.     

Determination of uranium in electro-refined plutonium by a combined ion-exchange and x-ray fluorescence technique

Uranium is separated from plutonium by adsorption on an anion-exchange resin from a concentrated hydrochloric acid solution and is eluted from the resin, collected on a disc of cation-exchange paper, and determined by X-ray fluorescence. The lower limit of detection is 2mug of uranium, and 50mug may be determined with a recovery of 98% and a standard deviation of 3.2mug. In plutonium metal, 19ppm of uranium were found, with a standard deviation of 2 ppm (6 results).     

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.     

Separation of iron-52 from chromium cyclotron targets on the 2% cross-linked anion-exchange resin AG1-X2 in hydrochloric acid

Iron-52 can be separated from solutions of chromium cyclotron targets by eluting chromium, copper and radioactive impurities with 9.0M hydrochloric acid from a column containing 1.0 g of AG1-X2 anion-exchange resin. Iron-52 is retained and can then be eluted with 6.0M hydrochloric acid containing 0.05M hydrogen iodide or 0.05M sodium iodide. The separations are sharp and quantitative. Less than 2 microg of chromium will remain with the iron-52, from 2.0 g originally present.     

Simultaneous determination of zirconium and hafnium in standard rocks by neutron activation analysis

A sensitive analytical technique has been developed to determine zirconium and hafnium at the 1 ppm and 0.01 ppm levels, respectively, in natural silicate matrices. The technique is based on the use of a Ge(Li) detector for high-resolution γ-ray spectrometry following irradiation with thermal neutrons. Simultaneous separation of both elements is achieved by addition of only zirconium carrier and use of a strongly basic anion-exchange resin. Hafnium was shown to follow zirconium throughout the chemical procedures. The chemical yield of the separation procedure was determined for each sample by use of an automated fast-neutron activation analysis system, which obviated the need to convert the separated zirconium to a conventional gravimetric weighing form. The method has been applied to the analysis of a variety of standard rocks and related natural materials.     

Separation of lead-203 from cyclotron-bombarded thallium targets by ion-exchange chromatography

A simple method is presented for the separation of lead-203 from copper-backed thallium cyclotron targets. The procedure involves cation-exchange chromatography in hydrochloric acid and hydrochloric acid-acetone mixtures. Further purification involves anion-exchange chromatography in nitric acid-hydrobromic acid mixtures. A cation-exchange column containing 3.0 g of resin can handle as much as 15 g of thallium and 160 mg of copper. An anion-exchange column containing 3.0 g of resin can separate lead from up to 200 mg of thallium and 10 mg of copper. Separations are extremely sharp and less than 0.1 mug of thallium and less than 0.1 mug of copper remain in the lead-203 fraction.     

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.     

Determination of uranium in natural waters after anion-exchange separation

A method is described for the determination of uranium by fluorimetry and spectrophotometry in samples of natural non-saline waters. After acidification with hydrochloric acid, the water sample is filtered and, following the addition of ascorbic acid and potassium thiocyanate, passed through a column of the strongly basic anion-exchange resin Dowex 1-X8 (thiocyanate form). On this exchanger uranium is adsorbed as an anionic thiocyanate complex. After removal of iron and other coadsorbed elements by washing first with a mixture consisting of 50 vol.% tetrahydrofuran, 40 vol.% methyl glycol and 10 vol.% 6 M hydrochloric acid, and then with pure aqueous 6 M hydrochloric acid, the uranium is eluted with 1 M hydrochloric acid. In the eluate, uranium is determined fluorimetrically or by means of the spectrophotometric arsenazo III method. The procedure was used for the routine determination of uranium in water samples collected in Austria.     

Chemical analysis of manganese nodules. Part I. Determination of seven main and trace constituents after anion-exchange separation

A method is described for the determination of Mn, Cu, Co, Zn, Cd, Pb and U in samples of manganese nodules. After dissolution of the sample in concentrated hydrochloric acid, the elements are adsorbed on a column of the strongly basic anion-exchange resin Dowex 1 from a medium consisting of 50 % (v/v) hexone, 40 % (v/v) isopropanol and 10 % (v/v) 12 M hydrochloric acid. After removal of iron by washing the resin bed with a mixture of the same composition, 6 M hydrochloric acid is passed through the column to elute Mn, Cu, Co, and Pb, and then 1 M hydrochloric acid and 2 M nitric acid to elute Zn, Cd and U. In the eluates the elements are determined by atomic-absorption spectrometry except for uranium which is determined by fluorimetry. The method was used successfully for the determination of mg and p.p.m. quantities of Mn, Cu, Co, Zn, Cd, Pb and U in 17 samples of manganese nodules from the Pacific Ocean.