Separation Of Thorium Research Articles

Differential-Kinetic Determination of Microamounts of Thorium in Soils

Microamounts of thorium in soils can be determined by a differential-kinetic method based on the kinetic properties of the complex of thorium with 1,2-cyclohexanediaminetetraacetic acid (ThDCTA). The thorium content was determined spectrophotometrically upon decomposition of this complex in 0.1 M HNO3 in the presence of Arsenazo III. The method involves anion-exchange isolation of Th from solution obtained by degradation of the soil material; it allows thorium determination in the presence of a number of impurities, which poses less stringent requirements on thorium separation from these impurities.

Column chromatographic separation of thorium(IV) from ascorbic acid medium using poly-(dibenzo-18-crown-6)

A simple separation method has been developed for thorium(IV) using poly-(dibenzo-18-crown-6) and column chromatography. The separation was carried out from ascorbic acid medium. The adsorption of thorium(IV) was quantitative from 0.001-0.01M ascorbic acid. The elution of thorium(IV) was quantitative with 4.0-8.0M HCl, 3.0-6.0M HClO4, 4.0-8.0M H2SO4 and 1.0-8.0M HBr. The capacity of poly-(dibenzo-18-crown-6) for thorium(IV) was found to be 1.379±0.01 m.mol/g of crown polymer. Thorium(IV) was separated from a number of cations in binary as well as in multicomponent mixtures. The method was extended to the determination of thorium in monazite sand. It is possible to separate and determine 5 ppm of thorium(IV) by this method. The method is very simple, rapid, selective and has good reproducibility (approximately ±2%).

Anion-Exchange Recovery of Thorium from Uranium: Analytical and Preparation Aspects

Recovery of thorium from U(VI) containing 20% 235U in 7 M HCl with AV-17-8 chs anionexchanger [GOST (State Standard) 20301-74] was studied using a Ge-Li detector. An 1 cm column in diam-eter with 40-cm resin bed height ensures complete thorium separation from 1 g of U sorbed on the resin. Thismethod is suitable both for monitoring in fuel elements Th, rare-earth elements, the other impurities unsorbed with strongly basic anion exchangers and for preparing 231,234Th research generators. Thorium is notsorbed with the above resin from 11 M HCl. From published stability constants of Th chloride complexes, the thorium speciation in 4 M HCl (ionic strength μ = 4) was calculated.

An innovative method for processing Egyptian monazite

The present work deals with a study of an innovative method for processing Egyptian monazite by alkaline leaching in ball mill autoclaves, where grinding and leaching of monazite take place simultaneously. This was followed by selective separation of thorium and uranium from lanthanides by autoclave leaching of the hydroxide cake obtained with ammonium carbonate–bicarbonate solutions. This method was based on the fact that thorium and uranium form soluble carbonate complexes with ammonium carbonate while lanthanides form sparingly soluble double carbonates. It was found that complete alkaline leaching of Egyptian monazite (99.8%) was attained at 150 and 175 °C within 2.5 and 1 h, respectively (satisfying favorable conditions of the hydroxide cake obtained for subsequent selective carbonate leaching). Monazite leaching was intensified and accelerated in ball mill autoclaves as a result of the grinding action of steel balls, removal of the hydroxide layer covering monazite grains and the continuous contact of fresh monazite surface with alkali solution. The study of selective carbonate processing of the hydroxide cake with ammonium carbonate–bicarbonate solutions revealed that the process must be carried out in an autoclave under pressure. Complete thorium recovery (99.4%) with uranium recovery (94.7%) and their separation from the lanthanides were attained at 70–80 °C during 1–2 h. The extraction of lanthanides in carbonate solution was low and did not exceed 1.5–2%. On the contrary, at atmospheric pressure, the recovery of thorium was low 18.4% at 70 °C. This is due to the instability of ammonium thorium carbonate complex, ammonium carbonate and bicarbonate and their dissociation with the liberation of ammonia, carbon dioxide and water vapor.

Use of extraction chromatography for thorium purification from Eskisehir-Beylikahir Thorium-REEs ore deposit

The extraction chromatography method was used to separate thorium from acidic leach solution. The separation of thorium was realized on silica gel column coated with tri-octlyphosphine oxide (TOPO). The extraction yield of thorium on this column from nitric acid leach solution is 91.9%. Then thorium was eluted by using 0.5 M H2SO4 solution, and elution yield was determined as 96.5%. The chemical analysis of H2SO4 fractions indicated that thorium was concentrated and purified succesfully by this method. As a result, thorium was recovered in dilute leach solution with a yield of 81.0±6.8%.

Separation and direct UV detection of lanthanides complexed with cupferron by capillary electrophoresis

Separation and detection of lanthanides by capillary zone electrophoresis in the presence of cupferron ( N-nitroso- N-phenylhydroxylamine) as UV absorbing complexing agent were investigated. The resolution of partially complexed positively charged cupferron complexes is improved by using a buffer ligand competing with cupferron for metal ions. When hydroxyisobutyric acid (HIBA) is used as buffer and competing ligand, it provides complete separation of all 14 lanthanides with good peak shapes. An on-column separation of 14 lanthanides was achieved in only 7 min using 0.1 mmol/l cupferron, 15 mmol/l HIBA at pH 4.9. The separation efficiencies for the optimum separation condition are between 77 000 and 208 000 theoretical plates. Determination of lanthanide complexes was performed by direct UV detection at 210 nm. Detection limits (signal-to-noise ratio=3) are ca. 0.24–0.47 μg/ml for lanthanides. Under optimum conditions, the complete separation of thorium and uranium from mixed lanthanides was achieved.

Separation of Thorium(IV) from Associated Elements Using Poly-(Dibenzo-18-Crown-6) and Column Chromatography from Picric Acid Medium

A simple column chromatographic method has been developed for the separation of thorium(IV) from associated elements using poly-(dibenzo-18-crown-6). The separations are carried out from picric acid medium. The adsorption of thorium(IV) was quantitative from 0.0005–0.05M picric acid. Amongst the various eluents tested, 2.0–8.0M HCl, HBr, 1.0–6.0M HClO4 and 5.0M acetic acid were found to be particularly efficient for the quantitative elution of thorium(IV). The capacity of poly-(dibenzo-18-crown-6) for thorium(IV) was found to be 1.29±0.01 mmol/g of crown polymer. Thorium(IV) was separated from a number of cations in binary mixtures in which most of the cations showed a very high tolerance limit. It was possible to separate thorium(IV) from a number of cations such as lanthanum(III), yttrium(III), uranium(VI), beryllium(II) and barium(II) in multicomponent mixtures. The method was extended to the determination of thorium in monazite sand. It is possible to separate and determine 5 ppm of thorium(IV) by this method. The method is very simple, rapid, selective and has good reproducibility (approximately ±2%).

Thorium adsorption behaviour on mixed ammonium lanthanum oxalate, LAOX

The cation-exchange properties of mixed ammonium lanthanum oxalate, LAOX, were studied by batch equilibration as a function of the concentration of some cations, such as alkaline earths or ammonium and of some anions and acids. The distribution coefficients for thorium are high, while U(VI) is not adsorbed over a large acidity range. Thus, the separation of thorium from uranium may be successfully carried out. The experimental conditions of adsorption, elution and recovery of thorium were investigated as well, by using chromatographic columns filled with LAOX, in order to set best the separation conditions from uranyl ions. Instrumental neutron activation analysis, ICP emission spectrometry and the UV spectrometry were used to evaluate the thorium, uranium and lanthanum concentrations.

Separation of 234Th from 90Y

A relatively simple procedure has been developed for the determination of 90Sr in natural aqueous samples. The method consists mainly of a Fe(III)-hydroxide co-precipitation step, followed by the separation of 90Y with the mixture of yttrium-oxalate and yttrium-ammonium-oxalate salts. This method was tested using a large number of natural water samples and 234Th contamination was observed in the prepared yttrium samples. The analysis has therefore been extended to include the separation of thorium from yttrium, which is made by DOWEX-50W-X8 cation exchange resin and citric acid as chelating agent. The experience and results of this new method are discussed.

Separation of thorium from aqueous solution using silk fibroin

In this study we investigate the basic features of thorium adsorption from aqueous systems by silk fibroin. Our previous study showed that this biopolymer has high efficiency for U(VI) adsorption. It is well-known that thorium, which is a tetravalent metal, is a more reactive element than uranium. Thorium(IV) adsorption proves to be very rapid and dependent on pH, temperature, retention time, concentration of ion, amount of fibroin, volume of solution and volume-to-mass ratio.

Separation of Thorium and Uranium from Silicate Rock Samples Using Two Commercial Extraction Chromatographic Resins

A new chemical separation technique to isolate Th and U from silicate rocks was established by using two kinds of commercial extraction chromatographic resins. In the first column procedure, with U/TEVA·spec resin, almost all elements except Th and U were eluted by 4 M HNO(3). Th was then separated by using 5 M HCl, and U was finally isolated by successive addition of 0.1 M HNO(3). A significant amount of Zr still remained in the Th fraction, which was then further purified in the second column stage using TEVA·spec resin. In the second procedure, Zr was eluted first by using 2 M HNO(3), and then Th was collected by 0.1 M HNO(3). Both the Th and U fractions obtained by these procedures were sufficiently pure for thermal ionization mass spectrometric (TIMS) analysis. Recovery yields of Th and U exceeded 90%, and total blanks were <19 pg for Th and <10 pg for U. Our method has advantages over previous methods in terms of matrix effects, tailing problems, and degree of isolation. Since Th and U are effectively separated without suffering any matrix interference from coexisting cations and anions, this technique can be used not only for the analysis of igneous rock samples but also for the analysis of soils, marine sediments, carbonates, phosphates and seawater, groundwater, and surface water.

Separation and determination of thorium, uranium and mixed rare-earth elements as their UV/Vis absorbing complexes by capillary zone electrophoresis

Separation and determination of thorium, uranium and mixed rare-earth elements (RE) as their 2-(2-arsenophenylazo)-1,8-dihydroxyl-7-(4-chloro-2,6-dibromophenylazo)-naphthalene-3,6-disulfonic acid (DBC-As) complexes by capillary electrophoresis is presented in this paper. The pre-column derivitization conditions are discussed. Some separation parameters such as pH value, type of carrier electrolyte, applied voltage, the concentration of ligand in buffer and the sample size are also optimized. Under the selected conditions, the complete separation of thorium and uranium from mixed RE was accomplished in 10 min. Quantitative analyses exhibited an excellent linear dynamic relationship in the range of over two orders of magnitude. Detection limits of 4.81×10 −8, 7.23×10 −8, and 59.4×10 −8 mol l −1 for RE, Th and U were obtained, respectively. This method was applied to the determination of these metal ions in ore samples.

Pre-concentration and separation of thorium, uranium, plutonium and americium in human soft tissues by extraction chromatography

An extraction chromatographic method is described for the pre-concentration and separation of thorium, uranium, plutonium and americium in human soft tissues. Tissues such as lung and liver are oven dried at 120°C, ashed at 450°C and the ashed sample is alternately wet (HNO3/H2O2) and dry ashed, and then dissolved in 8M HCl. Because of the complex matrix and large sample samples (up to 1500 g), the actinides were preconcentrated from the tissue solution using the TRUTM resin (EIChroM) prior to elemental separation by extraction chromatography and determination of americium, plutonium, uranium and thorium by alpha spectrometry. The actinides were eluted from the preconcentration column and each actinide was individually eluted on TEVATM and TRUTM resin columns in a tandem configuration. Actinide activities were then determined by alpha spectrometry after electrodeposition from a sulfate medium. The method was validated by analyzing human tissue samples previously analyzed for americium, plutonium, uranium and thorium in the United States Transuranium and Uranium Registries (USTUR). Two National Institute of Standards and Technology (NIST) Standard Reference Materials, SRM 4351-Human Lung and SRM 4352-Human Liver were also analyzed.

Investigation of thorium(IV) separation from cerium(IV) on a silica gel column coated with tri-octylphosphine oxide

The parameters effecting the efficiency of thorium extraction on silica gel coated with Tri-octylphosphine oxide(TOPO) such as; HNO 3 concentration, thorium concentration, TOPO concentration, flow rate and nature of diluent were studied and optimum conditions were determined. Various elution reagents were tried to elute thorium from the column. High recovery was obtained with 0.5 M H 2SO 4, 0.5 M HCl solutions. Extraction data have been used to separation thorium from iron(III) and Ce(IV). The solution that contains Fe(III), Ce(IV) and Th(IV) in nitric media was passed through the TOPO/silica gel column, whilst Th(IV) and Ce(IV) were extracted by TOPO, Fe(III) was not. Firstly Th(IV) was eluted with H 2SO 4 then Ce(IV) was eluted with HCl. As a result, optimum conditions are here reported for the separation of thorium from cerium(IV).

Column chromatographic separation of thorium (IV) from associated elements using poly-(dibenzo-18-crown-6) from sodium nitrate medium

A simple column chromatographic method has been developed for the separation of thorium from associated elements using poly-(dibenzo-18-crown-6). The separations are carried out from sodium nitrate medium. The adsorption of thorium was quantitative from 0.1-0.5M sodium nitrate. Amongst the various eluents tested, 1.0-8.0M HCl, HBr, H2SO4 and 3.0-8.0M HClO4 were found to be particularly efficient for e elution of thorium. The capacity of poly-(dibenzo-18-crown-6) for thorium was found to be 1.034 mmole/g of crown polymer. Thorium was arated from number of elements in binary mixtures in which most of the elements showed a very high tolerance limit. It was possible to separate tium from a number of elements in multicomponent mixtures. The method was extended to the determination of thorium in monazite sand and ga: artles. The method is very simple, rapid, selective and has good reproducibility (approximately±2%).

Separation of thorium, uranium and rare-earth elements with 2-[(2-arsenophenyl)-azo]-1,8-dihydroxy-7-[(2,4,6-tribromophenyl)azo]-naphthalene-3,6-disulfonic acid by capillary electrophoresis

The separation of thorium, uranium and rare-earth elements (RE) as their 2-[(2-arsenophenyl)-azo]-1,8-dihydroxy-7-[(2,4,6-tribromophenyl)azo]-naphthalene-3,6-disulfonic acid complexes by capillary electrophoresis with direct UV–Vis detection is presented in this paper. The influences of pH value and concentration of electrolyte, voltage and surfactant on separation were investigated and optimized. Under the selected conditions (30 mM NaAc–HCl buffer containing 0.5 mM cetyltrimethylammonium bromide and 0.2 mM chelating reagent, pH 4.30, 12 KV, 635 nm as detection wavelength), the coexisted ions were separated within 4 min, and limits of detection of 37, 39, 199 μg l −1 for RE, thorium, uranium with a linear dynamic range of over 2 orders of magnitude were achieved, respectively.

Sequential Separation and Trace Enrichment of Thorium(IV) and Uranium(VI) on Chelating Resin Amberlite XAD-2-ortho-vanillinthiosemicarbazone (o-VTSC)

ABSTRACT Polystyrenc-divinylbenzene-based Amberlite XAD-2 was funetionalized with ortho-vanillinthiosemicarbazone and its analytical properties were investigated. The resin was used successfully for the separation and preconcentration of thorium(IV) and uranium(VI) ions prior to their determination by spectrophotometry and by ICAP-AES and GF-AAS, respectively. The influence of several ions as interferents is discussed. The resin exhibits good chemical stability, reuseability, and a faster rate of equilibration for their determination. The proposed method has been applied to sequential chromatographic separation of thorium(IV) and uranium(VI) on river water samples with good analytical reliability such as recovery of 97–98%, relative standard deviation of 2–3%, and a detection limit of 100 ng-mL-1. The present method is also used for their determination in monazite sand and some standard geological materials.

Lanthanides Extraction by 8-Quinolinol and by a Mixture of Quinolinol and Trioctylphosphine Oxide

ABSTRACT The solvent extraction of Nd3+ , Sm3+, Eu3+ , Gd3+, Dy3+ , Ho3+ , and Er3+ from a M ionic strength medium (CH3COONa), pH (CH3COOH) by 8-quinolinol (HOx) and by a mixture of HOx and trioctylphosphine oxide (TOPO) in CCl4, CHCl3, C6H6, C6H5—NO2, C6H5—CH3 C6H5Cl and C6H5—Br is studied using titrimetric methods. A synergistic factor of over 10,000 is obtained. The atomic number and diluent effects are evident in the calculated formation constants and the lanthanide separation factors. A combination of the data obtained and that of Th4+ indicates that an excellent separation of thorium from the lanthanides can be obtained with this extraction system.

Extractive separation of thorium(IV) as a sulphate complex with N-n-octylaniline

The distribution of Th(IV) between aqueous sulphuric acid and organic phases of N-n-octylaniline in xylene is described. The dependence of the metal extraction on acidity and extractant concentration is investigated. Based on the results obtained, the possible extraction mechanism is discussed. The determination of Th(IV) and its separation from synthetic mixtures is suggested. The method is extended to the analysis of thorium in monazite and gas mantles.

Separation of Thorium from Uranium Product at the Tail End of Thorium Fuel Reprocessing Using Macroporous Cation-Exchange Resin

The utility of macroporous cation-exchange resins for the separation of uranium from thorium (relevant to the final purification of the product uranium after reprocessing of the thorium breeder fuel) was examined. Two such cation-exchange resins were studied and compared with a previously used gel-type resin. Batch experiments and column experiments were performed to generate equilibrium data and to optimize the procedure for the separation of U from Th under process conditions. Recovery and purity of the final product were the same while loading and washing rates were much higher (120 mL/h) than those used for gel-type resins (40 mL/h). Much higher throughput was achieved without losing product quality when macroporous resins were used instead of the gel-type resin.