The removal of thorium from aqueous solutions using zeolites

The ability of zeolites to remove thorium-232 from naturally radioactive thorium nitrate solutions was studied by ion exchange, adsorption and surface phenomena. The best zeolites were a clinoptilolite from Mudhills, California, USA and a mordenite rich tuff from Eastgate, Nevada, USA. As the concentration of thorium in solution was increased the mechanism of thorium removal switches from that of partial ion-exchange to a surface precipitation. This was confirmed by electron probe microanalysis (EPMA) in conjunction with XRD and Energy Dispersive X-ray analysis (EDX). A Langmuir-type of adsorption occurred with the thorium-232 daughter isotopes at the same time as partial exchange/precipitation of the thorium parent which is in regular equilibrium with its natural daughters. Some experiments with²³⁴Th were carried out to confirm this hypothesis as well as column experiments to confirm the usefulness of the Th removal.     

239+240Pu and137Cs distributions in seawater from the Yamato Basin and the Tsushima Basin in the Japan Sea

Comparative studies between column and batch liquid emulsion membrane techniques based on HDEHP/HCl system were carried out to develop a system for isolation of²³⁴Th from natural uranium. For column investigations a spray column was constructed and used with two different modes. In the first mode the feed solution was circulated through the membrane while in the second mode the membrane phase was circulated through the feed solution. The results showed that, kinetically, the equilibrium for thorium separation using batch technique is faster than the continous column system. Quantitative permeation of thorium was achieved within one minute of mixing whereby the permeation of uranium reached equilibrium after 3 minutes with a permeation percentage less than 6%. A procedure was developed to separate²³⁴Th from natural uranium with high radiochemical purity of more than 98%.     

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.     

Purification of 233U from Thorium and Iron in the Reprocessing of Irradiated Thorium Oxide Rods

A two step precipitation using ammonium carbonate and oxalic acid as the precipitants for thorium and iron is developed for the purification of ²³³U. Ammonium carbonate is added to the feed to increase the pH of the solution. The effect of pH on the solubility of U, Th and Fe in an excess of ammonium carbonate is studied. This indicates that the solubility of Th and Fe is minimum at pH 7 and the recovery of uranium is maximum. The effect of the concentration of thorium and iron on the recovery of uranium at pH 7 is studied. This indicates that the ammonium carbonate precipitation tolerates 2 g/l of thorium and 10 g/l of iron keeping losses of uranium to a minimum. If the feed solution contains more than a tolerable concentration of thorium the precipitation is followed in two steps: (1) Bulk of the thorium is removed by oxalate precipitation, (2) the remaining thorium and iron in the supernatant are removed by ammonium carbonate precipitation. A flow sheet is proposed for the purification of ²³³U from thorium and iron present in a strip product concentrate obtained during the reprocessing of irradiated thorium rods.     

A colorimetric determination of thorium

A colorimetric method for the determination of thorium is proposed. It is based upon the precipitation of thorium with a standard solution of oxalic acid and the subsequent reaction of the excess oxalic acid with a standard solution of potassium permanganate. The absorbancy of the remaining permanganate solution is directly proportional to the thorium present. The variables affecting this method have been critically studied. Reliable determinations can be made in the range of 3 to 30 mg of thorium in 1 cm cells when the colored solution is diluted to 250 ml. Most interfering substances can be removed by electrolysis in a mercury cathode cell or by the precipitation of thorium with potassium iodate.     

Column reversed-phase partition chromatography for the isolation of some radionuclides from biological materials

Revised-phase partition chromatography is a very useful tool for selective isolation of radionuclides from biological materials. Some new applications of this technique to the resolution of practical problems in radiation protection are reported. Natural thorium and enriched uranium can be determined separately and together in urine by means of a column of Microthene-710 supporting a solution of tri-n-octyl-phosphine oxide (TOPO) in cyclohexane; batchwise extraction processes with Microthene supporting TOPO are also successful. Strontium-90 is determined in urine by a batch extraction of yttrium-90 with a slurry of Microthene supporting the liquid cation exchanger di-(2-ethylhexyl)phosphoric acid. Only a wet mineralization of the urines is required and the analyses are simple, rapid and sufficiently accurate. A method for the isolation of iodine from foodstuffs with a Microthene-benzene column is also described.     

Determination of uranium and thorium in complex samples using chromatographic separation, ICP-MS and spectrophotometric detection

The paper describes a research of possible application of UTEVA and TRU resins and anion exchanger AMBERLITE CG-400 in nitrate form for the isolation of uranium and thorium from natural samples. The results of determination of distribution coefficient have shown that uranium and thorium bind on TRU and UTEVA resins from the solutions of nitric and hydrochloric acids, and binding strength increases proportionally to increase the concentration of acids. Uranium and thorium bind rather strongly to TRU resin from the nitric acid in concentration ranging from 0.5 to 5 mol L⁻¹, while large quantities of other ions present in the sample do not influence on the binding strength. Due to the difference in binding strength in HCl and HNO₃ respectively, uranium and thorium can be easily separated from each other on the columns filled with TRU resin. Furthermore, thorium binds to anion exchanger in nitrate form from alcohol solutions of nitric acid very strongly, while uranium does not, so they can be easily separated. Based on these results, we have created the procedures of preconcentration and separation of uranium and thorium from the soil, drinking water and seawater samples by using TRU and UTEVA resins and strong base anion exchangers in nitrate form. In one of the procedures, uranium and thorium bind directly from the samples of drinking water and seawater on the column filled with TRU resin from 0.5 mol L⁻¹ HNO₃ in a water sample. After binding, thorium is separated from uranium with 0.5 mol L⁻¹ HCl, and uranium is eluted with deionised water. By applying the described procedure, it is possible to achieve the concentration factor of over 1000 for the column filled with 1 g of resin and splashed with 2 L of the sample. Spectrophotometric determination with Arsenazo III, with this concentration factor results in detection limits below 1 μg L⁻¹ for uranium and thorium. In the second procedure, uranium and thorium are isolated from the soil samples with TRU resin, while they are separated from each other on the column filled with anion exchanger in alcohol solutions. Anion exchanger combined with alcohol solutions enables isolation of thorium from soil samples and its separation from a wide range of elements, as well as spectrophotometric determination, ICP-MS determination, and other determination techniques.     

Precipitation of metal 8-hydroxyquinolates from homogeneous solution—II Thorium

A comparison has been made of the precipitation of thorium with 8-hydroxyquinoline by the direct method of addition of reagent and by precipitation from homogeneous solution by generation of the reagent from 8-acetoxyquinoline. The latter reagent produces a thorium precipitate with superior physical characteristics. Separation studies using cerium^III as a diverse ion also indicate the superiority of the method using 8-acetoxyquinoline. Further studies of thorium 8-hydroxyquinolate, precipitated by either method, indicate that ignition to thorium oxide is a reliable way to conclude the determination. Methods involving weighing or brominating the 8-hydroxyquinolate generally furnish erroneous results.     

Preparation, characterization and application of thorium oxalate for sorption of plutonium and americium from aqueous solution

Synthetic inorganic exchangers exhibit good thermal and radiation stability. Thorium oxalate precipitate shows potential for co-precipitation of plutonium and americium from oxalate supernatant generated during plutonium oxalate precipitation. In the present study, efforts were made to prepare thorium oxalate precipitate to be used for column operation. Distribution ratios were determined to optimize conditions for sorption of plutonium and americium on thorium oxalate from nitric acid + oxalic acid solutions with composition similar to that of oxalate supernatant. Column experiments were also performed to evaluate the sorption capacity of thorium oxalate for plutonium and americium from the same medium. The result showed that, thorium oxalate prepared in 1.75M HNO₃ at 70 °C is suitable for column operations. These studies showed that plutonium and americium could be simultaneously removed from aqueous solutions with composition similar to plutonium oxalate waste using glass column packed with thorium oxalate and these nuclides could be recovered by eluting with 3M HNO₃.     

Determination of thorium isotopes in gas lantern mantles by alpha-spectrometry

A procedure for the determination of the three main isotopes of thorium in gas lantern mantles by alpha-spectrometry has been developed. The samples examined were dissolved in concentrated nitric acid and thorium was precipitated as hydroxide. Thorium was then dissolved in hydrochloric acid to be extracted into a TOPO solution, back-extracted with sulfuric acid, electrodeposited onto a steel disc and finally counted alpha-spectrometrically. The radiochemical recovery for thorium was 94% with a counting efficiency of 37%.     

Direktthermometrische bestimmung von thorium und lanthan in gläsern

A rapid method is described for the determination of thorium and lanthanum in non-silicate glasses. It is suitable for routine use in a works laboratory. The samples are dissolved in nitric acid. The thorium content is calculated from the measured heat of precipitation of thorium iodate, and the lanthanum content by difference from the heat of precipitation of both thorium and lanthanum oxalates together. The apparatus is calibrated by using standard solutions of the two metal ions. The standard deviations for the middle of the range (around 250 mg of the oxides) were 3·1 mg for ThO₂ and 1·7 mg for La₂O₃. An analysis takes about 1·5 hr.     

Ion exchange separation in the analysis of bismuth base alloys : Part II. Ternary alloys containing uranium and thorium

Procedures are described for the analysis of bismuth base alloys containing uranium and thorium in the range from 0.1 to 10%. The thorium is first separated by the passage of a solution of the sample in 5M hydrochloric acid through a column of Deacidite FF in the chloride form. For thorium contents greater than about 1%, the determination is completed volumetrically with EDTA using pyrocatechol violet as the indicator. Smaller amounts are determined absorptiometrically by the thoronol method. Uranium is recovered from the ion-exchange column in a quantity of 0.2M hydrochloric acid, bismuth still being retained by the column under these conditions. Uranium contents greater than about 1% are determined volumetrically after reduction to the tetravalent state with a lead reductor, whilst smaller amounts are determined polarographically using a tartrate base solution.     

PMBP-loaded polyurethane foam as an extractant for thorium nitrate from aqueous solution

A study on extraction of thorium with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (PMBP)-loaded polyurethane foam is described. Open-cell polyurethane foam has proved to be effective as supporting material for PMBP. Thorium nitrate can be quantitatively extracted by PMBP-loaded polyurethane foam over a wide pH range. The effect of equilibrium time, pH, thorium concentration, various anions and flow-rate on the extraction efficiency of thorium is examined. A technique of extraction chromatography column with PMBP foam cylinder has been developed for trace thorium analysis of bulky water samples.     

Method for the isolation of thorium from siliceous materials

A method for the isolation from siliceous materials of carrier-free chemically and radiochemically pure thorium is described. The method was applied and tested on several shale and deep-sea sediment samples used in the application of the Thorium Isotopes Method to the Dating of Marine Sediments. The chemical procedure consistently produces pure thorium in good yields. Several samples can be prepared simultaneously in a few hours.     

A remote system for the separation of228Th and224Ra

A system was developed which enables the user to separate remotely²²⁸Th from its daughters using a hot cell. The thorium is adsorbed on an anion exchange resin and the daughters elute through the column. The radium and its daughters can then be loaded on a generator outside of the hot cell. The radium is obtained quantitatively with virtually no breakthrough of the thorium parent. Subsequent to the separation, the thorium can be recovered quantitatively from the column.Work supported by the Office of Health and Environmental Reseach, U.S. Department of Energy and Division of Cancer Treatment, National Cancer Institute.Deceased.     

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.

     

A titrimetric method for the sequential determination of thorium and uranium

A method for the sequential determination of thorium and uranium has been developed. In the sample solution containing thorium and uranium, thorium is first determined by complexometric titration with ethylenediaminetetraacetic acid (EDTA) and then in the same solution uranium is determined by redox titration employing potentiometry. As EDTA interferes in uranium determination giving positive bias, it is destroyed by fuming with HClO₄ prior to the determination of uranium. A precision and accuracy of better than ±0.15% is obtained for thorium at 10mg level and uranium ranging from 5 mg to 20 mg in the aliquot.     

Neutron activation analysis of microgram amounts of thorium in uranium ores and process liquors by means of thorium-233

A method is described for neutron activation analysis of thorium by employing thorium-233. Decontamination steps include anion exchange in 12.5 N HCL, precipitation of fluoride, extraction with mesityl oxide and thorium oxalate precipitation. The time spent is less than 1 h; spurious activities in counting samples amount only to 2% and can easily be corrected for. The sensitivity of the method is ca. 0.02 μg of thorium in a neutron flux of 10¹²n/cm²/sec with an irradiation time of 5 min.     

Procedures for isolation and determination of thorium

The cation-exchange behaviour of micro and trace quantities of thorium on Dowex 50-X8 in the presence of carbonate and phosphate has been studied. Carbonate causes loss of thorium to the column effluent at pH 10.In the presence of phosphate, thorium is incompletely sorbed in the pH range 2-4.5, the loss being maximum at pH 3.8. Outside this range, thorium is quantitatively sorbed and recovered. A method that does not employ ion-exchange has been developed for the microdetermination of thorium in phosphate solution. The phosphate is precipitated as bismuth phosphate and thorium is leached from the precipitate with ammonium carbonate solution and determined with Arsenazo III. Uranium, molybdenum and vanadium are removed with Alamine 336. The results obtained for a standard ore are in excellent agreement with the certified value.     

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.