Transport of uranium free particles in a d.c. arc plasma burning in air at atmospheric pressure

The transport parameter ψ was calculated for the free particles of uranium in a d.c. arc plasma burning in air. Using the “wire method” the volatilization rate (Q_w), the total concentration of free particles (_nt), the axial velocity (_vj) of uranium particles and the plasma cross section (S) were measured. The transport parameter was calculated for cylindrical symmetry of the arc. The total particle concentration calculated by the wire method was compared to values obtained by absolute intensity measurements of ion and atom spectral lines of uranium. This led to an estimate of the molecular concentration of uranium in the d.c. arc plasma.     

Recovery of uranium and thorium from zirconium oxychloride by solvent extraction

A solvent extraction process is proposed to recover uranium and thorium from the crystal waste solutions of zirconium oxychloride. The extraction of iron from hydrochloride medium with P350, the extraction of uranium from hydrochloride with N235, and the extraction of thorium from the mixture solutions of nitric acid and the hydrochloric acid with P350 was investigated. The optimum extraction conditions were evaluated with synthetic solutions by studying the parameters of extractant concentration and acidity. The optimum separation conditions for Fe (III) are recognized as 30% P350 and 4.5 to 6.0 M HCl. The optimum extraction conditions for U (VI) are recognized as 25% N235 and 4.5 to 6.0 M HCl. And the optimum extraction conditions for Th (VI) are recognized as 30% P350 and 2.5 to 3.5 M HNO₃ in the mixture solutions. The recovery of uranium and thorium from the crystal waste solutions of zirconium oxychloride was investigated also. The results indicate that the recoveries of uranium and thorium are 92 and 86%, respectively.     

Liquid-liquid extraction of Th4+ and UO 2 2+ by LIX-26 and its mixtures

Solvent extractions of thorium(IV) and uranium(VI) by a commercially available chelating extractant LIX-26 (an alkylated 8-hydroxyquinoline) or 8-hydroxyquinoline, benzoic or salicylic acid, dipentyl sulphoxide (DPSO) and their mixtures with butanol as modifier in benzene/methylisobutyl ketone (MIBK) as the diluent have been studied. Extraction of uranium(VI) by 10% LIX-26 and 10% butanol in benzene becomes quantitative at pH 5.0. The pH 0.5 values for the extraction of thorium(IV) and uranium(VI) are 4.95 and 3.35, respectively. Quantitative extraction of thorium(IV) by the mixture of 0.1 M oxine and 0.1 M salicylic acid in methylisobutyl ketone was observed at pH 5.0. The influence of concentration of various anions on the extraction of Th⁴⁺ by mixtures of LIX-26 and benzoic acid has been studied. Studies on extraction of thorium(IV) and uranium(VI) by mixtures of LIX-26 (HQ) and DPSO show that the extracted species are possibly of the type [ThQ₂/DPSO/₂/SCN/₂] and [UO₂Q₂/DPSO/], respectively.     

Assessment of the natural radioactivity using two techniques for the measurement of radionuclide concentration in building materials used in Japan

The specific activities of ²³⁸U, ²³²Th, and ⁴⁰K in selected building materials used in Japan were measured using a high-purity germanium detector. The uranium and thorium concentrations were determined from same samples using inductively coupled plasma mass spectrometry. There was a good agreement between the measurement of uranium and thorium with both methods (R ² = 0.94, and 0.97, respectively). Based on the specific activities, we have estimated some hazard indexes such as radium equivalent activities (Ra _eq), external hazard index (H _ex), internal hazard index (H _in), annual gonadal equivalent dose (AGED), internal alpha dose, mass exhalation rate and emanation coefficient of radon.     

Effect of complexants on the adsorption and color reactions of lanthanum(III), uranium(VI), thorium(IV), and zirconium(IV) with Arsenazo M in the solid phase of an ANKB-50 fibrous ion-exchanger

The effect of complexants—acetic, aminoacetic, tartaric, malonic, and oxalic acids; EDTA; and Na₂CO₃—on the adsorption and subsequent determination of thorium(IV), lanthanum(III), uranium(VI), and zirconium(IV) with Arsenazo M in the solid phase of polyacrylonitrile fiber filled with an ANKB-50 anion exchanger was studied. Complexing agents were introduced into the solution at the step of metal ion adsorption. It was shown that zirconium and uranium interacted with the iminodiacetate groups of the adsorbent in the course of adsorption; the adsorption of elements from 10^?3 to 10^?2 M complexant solutions (except for tartaric and oxalic acids and EDTA) under the optimum conditions was enhanced as compared to their adsorption from pure solutions; complexation with Arsenazo M in the solid phase proceeded at a higher acidity than in the solution. When the elements were present simultaneously, their total concentration and individual thorium could be determined from malonic acid solutions with Arsenazo M by varying the concentration of acid and the adsorption pH.     

Ultratrace analysis of uranium and thorium in glass

It is today a most common phenomenon that ultratrace analyses for quality control have to be carried out in industrial laboratories far from optimum conditions and in spite of the lack of best suited equipment. It was against this setting that the development of a method for the photometric determination of uranium- and thorium-traces in glasses with arsenazo III was envisaged. The method basically consists of a digestion with HF/HClO₄/H₃BO₃, an extractive preseparation of interfering Ti- and Zr-traces with TTFA/hexanol/CCl₄, an extractive separation of U- and Th-traces with TTFA/TBP/toluene and a final determination of thorium alone (in the presence of photometrically inactive U(VI)) and the sum of Th+U(IV) with arsenazo III.The concentration of uranium is calculated from the difference of the sum of both traces minus the thorium content. Uranium can be determined with nearly the same sensitivity as thorium after reduction to uranium(IV). The most suitable reducing agent for uranium(VI) to uranium(IV) is a mixture of Na₂S₂O₄/CH₂O. An optimization of the arsenazo III concentration for the determination of thorium and uranium yielded an optimal concentration of 80 mg/L arsenazo III: For the reduction of uranium concentrations of 2 g/L of Na₂S₂O₄ and 3.2 g/L CH₂O proved to be optimal. Interferences of this photometric end determination by titanium, zirconium and scandium were investigated quantitatively. The permissible excess for these elements was found to be so low that a trace-trace separation method proved to be necessary. Separation methods were checked for the separation of the matrix components of the investigated glasses from thorium and uranium. One of these methods was suitable after optimization: thorium and uranium are extracted with TTFA/TBP/toluene from a solution containing hydrochloric acid. Back-extraction is carried out with HCl/KMnO₄. For the separation of titanium- and zirconium-cotraces an extra separation method had to be developed: they are extracted with TTFA/hexanol/CCl₄ before the separation of uranium- and thorium-traces from the matrix. The glasses were digested with HF/HX. Fluoride from the hydrofluoric acid is incompletely removed by evaporation and interferes with the extraction of uranium and thorium due to complex formation. Depending on the digestion variant used 162 to 0.23 mg F^– remain in the residue of the digestion of a 5 g sample. This interference was eliminated by a digestion with HF/HClO₄/H₃BO₃ and masking of residual fluoride with AlCl₃.Abbreviations used Arsenazo III 1,8-Dihydroxynaphthalene-3,6-disulphonic acid-2,7-bis [(azo-2)-phenylarsonic acid] - Arsenazo I 1,8-Dihydroxynaphthalene-3,6-disulphonic acid-2-[(azo-2)-phenylarsonic acid] - BPAP 2- (5-Bromo-2-pyridy] azo)-5-diethylaminophenol - EDTA Ethylenediaminetetraacetic acid - HX Designation for a high boiling mineral acid - FAAS Flame atomic absorption spectrometry - FOD 1,1,1,2,3,3,-Heptafluor-7, dimethyl-4,6-octanedione - GFAAS Graphite furnace atomic absorption spectrometry - ICP-MS Inductively coupled plasma — mass spectrometry - ICP-OES Inductively coupled plasma — optical emission spectrometry - LAS Liquid absorption spectrophotometry (classical photometry) - m(Th) Mass of thorium - NAA Neutron activation analysis - pK_Diss Negative logarithm to the base 10 of the dissociation constant of a complex - TBP Tri-(n-butyl)-phosphate - TOPO Tri(n-octyl)-phosphinoxide - TTFA 1-(2-Thenoyl)-3,3,3-trifluoroacetone     

Extraction chromatographic separation of thorium (IV) with tri-n-octylphosphine oxide (TOPO)

Thorium was extracted from a mixture of nitric acid and NaNO₃ of 0.01M each at pH 2.2 on a column of silica gel coated with TOPO. Thorium was separated from alkalis, alkaline earths, chromium, iron, cobalt, nickel, zinc, cadmium, mercury, lead, trivalent rare earths, platinum group metals, chloride, phosphate and acetate in binary mixtures by selective extraction of thorium. Thorium was separated from cerium (IV), zirconium, uranium and molybdenum by selective elution of thorium with 0.01M H₂SO₄. The method was extended for the analysis of thorium in monozite ore.     

Zur Abtrennung und Dekontamination von Uran aus salpetersauren Spaltproduktlösungen mit Anionenaustauschern

Weight distribution coefficients for U(VI) against Dowex 1 and Dowex 2 in HCl/HNO₃ and practical column-exchange capacities under defined conditions were determined. The behaviour of thorium, protactinium, iron, zirconium, niobium, ruthenium, and tellurium in the same system was studied in column experiments. The results of these determinations are discussed. An ion exchange procedure for enrichment and decontamination of uranium from fission products and thorium containing nitric acid solutions with the aid of a simple remoted handling apparatus is described.     

High performance liquid chromatographic studies on lanthanides, uranium and thorium on amide modified reversed phase supports

The retention behavior of uranium, thorium and lanthanides has been investigated with amide modified reversed phase C₁₈ supports using α-hydroxy isobutyric acid (α-HIBA) as the mobile phase. Four structurally different amide moieties namely, 4-hydroxy-N,N-dihexyl butyramide (4HHBA), 4-hydroxy-N,N-di-2-ethylhexylhexanamide (4HEHHA), bis(N,N,N′,N′-2-ethylhexyl)malonamide (B2EHM) and N-methyl-tris(dihexylcarbamoyl-3-methoxy)pivolamide (MTDCMPA) have been synthesized and studied. Among the various amide coated columns, the supports modified with 4HHBA, B2EHM and MTDCMPA exhibit an interesting retention for uranium and thorium, which is different from 4HEHHA modified support. The retention time for uranium and thorium increases with increasing amide concentration for 4HHBA, B2EHM and MTDCMPA supports, while the same decreases with increasing 4HEHHA content. However, the separation factor for uranium and thorium is greater on a 4HEHHA support, compared to an unmodified C₁₈ column, reflecting the amide's preferential complexation of uranium over thorium.Columns modified with 4HHBA, B2EHM and MTDCMPA exhibit relatively higher retentions for lanthanides. However, MTDCMPA modified support shows a different elution profile for lanthanides compared to 4HHBA, and B2EHM modified columns. Individual separations of heavier lanthanides, i.e., from gadolinium to lutetium also have been achieved using 4HHBA and B2EHM modified supports.The influence of modifier content, mobile phase concentration and its pH on the retention of metal ions has also been studied. Based on these investigations, an efficient high performance liquid chromatographic method (HPLC) has been developed for the rapid separation of uranium from thorium as well as for the individual separation of heavier lanthanides.     

Extraction of U(VI), Th(IV) and some fission products from nitric acid medium by sulfoxides and effect of γ-irradiation on the extraction

The extracting abilities for thorium, uranium and some fission products by five sulfoxides are given. The results show that di(2-ethylhexyl) sulfoxide (DEHSO) is not only completely miscible with kerosene, but also superior to tri-n-butyl phosphate in some properties. The extraction behavior of uranium, thorium and some fission products such as zirconium, niobium and ruthenium from aqueous nitric acid with DEHSO in kerosene has been studied over a wide range of conditions. DEHSO extracted uranium and fission products better than TBP under all conditions and is similar to TBP in extraction of thorium. A study of extraction mechanism indicates that U and Th are extracted as disolvates, whereas HNO₃ is extracted as monosolvate. Extraction of the two actinides decreases with increasing temperature, indicating the extraction to be exothermic. Preliminary studies show that -ray irradiated DEHSO extracts Zr and Nb to a smaller extent than irradiated TBP in the range of 10⁴–10⁷ rad.     

Unusual metalloporphyrins : thorium and uranium complexes of octaethylporphyrin.

The action of thorium or uranium tetrachloride with octaethylporphyrin [(oep)H₂] affords the dichlorometal (IV) complexes [M(IV)(oep)Cl₂, L_n] (M(IV) = Th or U, L = benzonitrile, tetrahydrofuran or pyridine). Spectral properties of these complexes are in good agreement with a cis octa-coordination.     

The analysis of zirconium-thorium binary alloys

Thorium-zirconium binary alloys are analysed by complexometric procedures. For alloys containing more than 20% thorium or 5% zirconium by weight, the sum of the constituents is obtained by a back titration procedure at pH 2.6–2.8 with bismuth nitrate using xylenol orange as indicator. Thorium is then masked with sulphate and the liberated EDTA is titrated with bismuth at pH 1.2–1.3. For alloys containing less than 20% of thorium, thorium fluoride is precipitated on lanthanum fluoride to effect its separation before titration. For alloys containing less than 5% of zirconium, the zirconium is separated by precipitation with p-bromo-mandelic acid.     

Separation studies of uranium and thorium using tetra(2-ethylhexyl) diglycolamide (TEHDGA) as an extractant

The extraction behavior of uranium, thorium and nitric acid has been investigated for the TEHDGA/isodecyl alcohol/n-dodecane solvent system. Conditional acid uptake constant (K _H) of TEHDGA/n-dodecane and the ratio of TEHDGA to nitric acid were obtained as 1.72 and 1:0.96, respectively. The extracted species of uranium and thorium in the organic phase were found to be UO₂(NO₃)₂·2TEHDGA and Th(NO₃)₄·2TEHDGA. A workable separation factor (D _Th/D _U) of the order of 300 was observed between thorium and uranium in the nitric acid range of 0.5M to 1.5M. Similar separation factor was also achieved at higher acidity when thorium was present in large concentration compared to uranium. These results indicate that TEHDGA solvent system could be a potential candidate for separation of thorium from uranium.     

Determination of trace concentrations of thorium in uranium oxide matrix by epithermal instrumental neutron activation analysis

An epithermal instrumental neutron activation analysis (EINAA) method using cadmium filter was standardized to determine trace concentrations of thorium in four samples of uranium oxide (U₃O₈) samples. Samples and thorium standards, wrapped with cadmium foil, were irradiated at a reactor neutron flux of about 10¹² cm^?2 s^?1. Radioactive assay was carried out using a Compton suppressed anticoincidence gamma ray spectrometer consisting of HPGe-BGO detectors coupled to MCA. Concentrations of thorium in these samples were found to be in the range of 15–72 mg kg^?1. EINAA results were validated by determining thorium concentrations in uranium matrix by standard addition method. EINAA results were compared with those obtained by two wet chemical methods namely ion chromatography (IC) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The results obtained by the three methods were found to be in good agreement, indicating further validity of the proposed EINAA method.     

Use of organic reagents in inorganic analysis

Summary Paper chromatography of cobalt, palladium, uranium, thorium, and zirconium/1-nitroso-2-hydroxy-3-naphtholates which are quantitatively precipitated, has been studied. As most of the complexes were not soluble in organic solvents, their hydrochloric acid solutions and solution of the cobalt, palladium, and uranium complexes in ammonium hydroxide were used for spotting. A large number of developing solvents were tried both on plain and salt-impregnated papers. A solvent mixture containing 60% acetone, 38% isobutyl alcohol and 2% 12N HCl, by volume was found suitable for the resolution of a mixture of complexes of cobalt, palladium, and uranium on plain paper. Thorium and zirconium complexes, however, did not move appreciably with any of the solvent mixtures tried. The paper impregnated with salt solutions did not show any improvement in the separation. The effect of HCl in the above solvent mixture on the separation of cobalt, palladium, and uranium, was also studied. It was observed that a small amount of HCl was necessary in this developing solvent for the migration of the metals, a large excess of this acid, increases their R_f values and these are brought so close that the separation of the metals becomes difficult. The colour of the cobalt, palladium, and uranium spots on the developed chromatograms indicated that the metals migrated as their complexes. Similar experiments were done with free metals ions, which gave different R_f values and this confirmed the fact that it was the metal complexes that moved and these complexes were stable under the conditions of the experiment. Precipitation of Co, Pd and U with 1-nitroso-2-hydroxy-3-naphthoic acid is quantitative and the paper chromatographic experiment affords a convenient method of concentrating the metal ions.Part IV: See Z. anal. Chem. 155, 241 (1957).     

Successive uranium and thorium adsorption from Egyptian monazite by solvent impregnated foam

The present work deals with uranium and thorium recovery from the Egyptian monazite sulfate leach liquor using the extraction chromatography technique (solvent impregnated material), where tributylamine (TBA) and di-n-octylamine (DOA) solvents were impregnated onto foam uranium and thorium separate recovery. The calculated theoretical capacities of the latter solvents were about 1.4 gU/g foam and 1.6 gTh/g foam, respectively. The attained uranium and thorium adsorption efficiencies (using ion-exchange columnar technique) were about 75 and 70% of its theoretical capacities, respectively. Using 1 M NaCl–0.1 M H₂SO₄ and 2 M H₂SO₄ as eluent solutions for uranium and thorium from the loaded solvents impregnated foam gave 95.8 and 98.7% elution efficiencies, respectively.     

Extraction of lanthanoids and some associated elements by mono-(2-ethylhexyl)phosphoric acid and their separations

Mono-(2-ethylhexyl)phosphoric acid (H₂MEHP) has been used to study the extraction of some lanthanoids and other associated elements from nitric acid medium. Effect of various variables like kind of diluent, concentration of metal ion, nitric acid and extractant has been investigated. Based on distribution data, it was possible to achieve some separations of lighter lanthanoids from metals like titanium, zirconium, thorium and uranium with high separation factors.     

Solid phase extraction and preconcentration of uranium(VI) and thorium(IV) on Duolite XAD761 prior to their inductively coupled plasma mass spectrometric determination

A simple and effective method is presented for the separation and preconcentration of thorium(IV) and uranium(VI) by solid phase extraction on Duolite XAD761 adsorption resin. Thorium(IV) and uranium(VI) 9-phenyl-3-fluorone chelates are formed and adsorbed onto the Duolite XAD761. Thorium(IV) and uranium(VI) are quantitatively eluted with 2 mol L⁻¹ HCl and determined by inductively coupled plasma-mass spectrometry (ICP-MS). The influences of analytical parameters including pH, amount of reagents, amount of Duolite XAD761 and sample volume, etc. were investigated on the recovery of analyte ions. The interference of a large number of anions and cations has been studied and the optimized conditions developed have been utilized for the trace determination of uranium and thorium. A preconcentration factor of 30 for uranium and thorium was achieved. The relative standard deviation (N = 10) was 2.3% for uranium and 4.5% for thorium ions for 10 replicate determinations in the solution containing 0.5 μg of uranium and thorium. The three sigma detection limits (N = 15) for thorium(IV) and uranium(VI) ions were found to be 4.5 and 6.3 ng L⁻¹, respectively. The developed solid phase extraction method was successively utilized for the determination of traces thorium(IV) and uranium(VI) in environmental samples by ICP-MS.     

Electron density calculations derived from the energy balance equation in a d.c. arc plasma burning in air

The Elenbaas-Heller equation was used to calculate the spatial distribution of electron densities ($\text{n}$_e(itR.z)) in a d.c. arc plasma burning in air at atmospheric pressure. Uranium, thorium, zirconium and a number of rare-earths were introduced as oxides into the plasma. The temperature and the electric field gradients were measured axially and radially. Electron densities were then derived from the calculated mean electrical conductivity ($\text{σ}$_(R.z)). The resulting electron density values were compared with values derived from Saha's equation for ionization processes.     

Gravimetric determination of uranium(vi) with n-benzoylphenylhydroxylamine

Uranium(VI) can be quantitatively precipitated by N-benzoylphenylhydroxylamine at pH 5.4. The precipitate is weighed after ignition to U₃O₈, or directly as U0₂(C₁₃H₁₀O₂N)₂. Cerium(III). thorium, lead and bismuth can be masked with magnesium-EDTA complex. Iron(IlI), titanium (IV) zirconium and molybdenum(Vl) and small amounts of aluminium can be precipitated with the reagent and filtered before uranium(Vl) is determined in the filtrate by proper adjustment of acidity. Fluoride, carbonate and organic acids interfere.