Extraction properties of octaethyltetraamidopyrophosphate (OETAPP)

The extraction of uranium was studied in the system of 0.1 M OETAPP in CHCl₃/HCl or HNO₃. The distribution coefficients of HCl and HNO₃ were calculated as a function of OETAPP concentration. The amount of OETAPP in the aqueous phase containing HCl and HNO₃ was found from the measurements of surface tension of this phase. The distribution of HCl and HNO₃ between an organic and aqueous phase was studied as a function of the concentration in the aqueous phase of the acid in question. The solvation energy of the extracted complexes was calculated on the basis of the measured potential differences. The cohesion and adhesion energies of the studied systems are given as well.     

Adsorption behaviour of some actinides on zirconium phosphate stability constant determinations

The adsorption behaviour of thorium, protactinium, uranium, neptonium and plutonium on zirconium phosphate from nitric acid and ammonium nitrate solutions was investigated. Partition data from the mentioned media together with that from chloride solutions were used to calculate formation constants for the concerned elements in the range of Cl⁻ and NO ₃ ⁻ activities <1M. Obtained β values were compared with those reported in the literature and indicated reasonable agreement.     

Coated wire thorium ion selective electrode: Part I

Coated wire ion selective electrode for thorium ion selective potentiometry was developed. Thorium ion selective coated wire electrodes were prepared by depositing a membrane comprising of Aliquat-336 loaded with Th(NO₃)₆²⁻ ions and poly vinyl chloride in varying proportion. A linear near-Nernstian response with a slope of −29.5 ± 0.3 mV over thorium concentration range of 1 × 10⁻¹–3 × 10⁻⁵ M in constant total nitrate concentration of 6 M was obtained for the electrodes of almost all the composition studied. In spite of small drift in response potential from composition to composition, day to day as well as from electrode to electrode, the slope of potential response line was constant within experimental error. Moreover, the electrode once prepared could be conveniently used over a period of one and half month.     

Conductometric estimation of thorium in dilute thorium chloride

Summary Conductometric titrations of thorium chloride against oxalic acid, ammonium oxalate and silver nitrate have been carried out at high dilutions (0.001, 0.0005 and 0.00033 M) of the chloride. Oxalic acid is found to be a suitable titrant for rapid estimation of thorium, the minimum error being +0.5%. The other titrants do not give good results. The titrations with ammonium oxalate indicate the step-wise ionisation of ThCl₄ into ThCl₂ ²⁺, ThCl³⁺ and Th⁴⁺. For mixtures of thorium chloride and cerous chloride, only the equivalence point corresponding to complete precipitation of both thorium and cerium is indicated.The authors express their sincere thanks to Prof. S. S.Joshi for his keen interest in this work and to Dr. G. S.Deshmukh for his advice and help in so many ways during the progress of these studies.     

Solvent extraction separation of hafnium with 4-methyl-3-pentene-2-one

A new method for the extractive separation of hafnium from zirconium is presented. Zirconium is extracted with pure mesityl oxide from 4M nitric acid/4M sodium nitrate medium, followed by extraction of hafnium with mesityl oxide from 0.4M hydrochloric acid/2M ammonium thiocyanate medium. It is possible to accomplish clean separations of Hf from Zr in ratios from 1:20 to 1:200. The separation of hafnium from commonly associated elements such as scandium, yttrium, uranium, thorium, alkali and alkaline earth metals in 500:1 weight ratio to hafnium is also possible.     

Coordination around thorium(IV) in aqueous perchlorate,chloride and nitrate solutions

The coordination around the thorium(IV) ion in aqueous perchlorate, chloride and nitrate solutions has been determined from large angle X-ray scattering measurements. In perchlorate solutions, where inner-sphere complexes are not formed, the first coordination sphere contains 8.0±0.5 water molecules with Th-H₂O bond lengths of 2.48₅ Å. In chloride solutions inner-sphere complexes are formed, which lead to an increase in the coordination number. In nitrate solutions the nitrate ions are bonded as bidentate ligands to the thorium ion. The bond lengths are similar to those found in crystalline hydrates of thorium nitrate. The coordination numbers found for thorium(IV) in solution are compared with previously reported values for lower charged ions of similar size.On leave from Department of Inorganic Chemistry Royal Institute of Technology S-10044 Stockholm Sweden     

Extraction of pertechnetate anion as a ligand in metal complexes with tributylphosphate

The extraction of the pertechnetate anion has been investigated in the systems tributylphosphate (TBP)—solvent (carbon tetrachloride, n-heptane, chloroform)—metal salt (uranyl nitrate and chloride, thorium nitrate)—ammonium salt. In the absence of a metal, the solvates HTeO₄. iTBP (i=4) are extracted, while in the presence of uranium and thorium, the distribution of technetium corresponds to the formation of the mixed complexes: UO₂(NO₃)(TeO₄)·2TBP, UO₂Cl(TcO₄)·2TBP and Th(NO₃)₃ (TcO₁)·2TBP. The effective constants of the reactions H⁺+TcO ₄ ⁻ +i(TBP)_org←(HTcO₁·iTBP)_org, and (ML_n·2TBP)_org+TcO ₄ ⁻ ←(ML_n−1TcO₄·2TBP)_org+L were established in the above systems. The extraction of pertechnetate ion is more effective when it is coordinated to a cation solvated by TBP than the extraction in the form of pertechnetate acid solvated by TBP.     

Coagulation of silver halide sols by thorium nitrate in the presence of potassium nitrate and potassium sulfate

Summary When silver iodide, silver bromide and silver chloride solsin statu nascendi are coagulated by thorium nitrate in the presence of potassium nitrate, three coagulation maxima appear. Two of them are identical with maxima that are found in absence of KNO₃, denoted with (II) and (IV) in fig. 1. The new maximum appears in the stability region of recharged sols (III). It is believed that this maximum is also—as maximum (IV)—caused by the coagulation of recharged silver halide sols by nitrate ions. Appearance of two nitrate coagulation maxima is explained by different charge densities on sol particles at various concentrations of Th(NO₃)₄ where they are formed. The new maximum indicates a lower charge density of sol particles. The possibility that the new maximum could have been caused by ionic complex species between thorium and nitrate ions has been rejected for data are available that the equilibrium constant for such complexes is small. In the presence of K₂SO₄ the coagulation effects of thorium nitrate on silver halide sols are markedly different. In acidified solutions only one coagulation maximum appears at rather high thorium nitrate concentrations [∼ 10⁻³ N Th (NO₃)₄] and the sol remains negatively charged [up to ∼ 10⁻² N Th (NO₃)₄] This is explained by complex formation of Th-ions and sulfate ions whereby ionic species of lower charge are formed, which exert a weaker coagulation effect. In neutral solutions another maximum at lower concentration of Th (NO₃)₄ is formed which appears to be the usual coagulation maximum produced by hydrolyzed thorium ions. The antagonistic effects of the salt pair Th (NO₃)₄-K₂SO₄ upon the coagulation of silver halides has been discussed and we have concluded that the large effects repeatedly reported can be explained not by simple electrostatic effects of ions in solution but rather by the formation of complexes between Th- and SO₄-ions.

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Zusammenfassung Die Koagulationseffekte des Thoriumnitrats in Anwesenheit von Kaliumnitrat und Kaliumsulfat an Silberhalogenid-Solenin statu nascendi wurden ausführlich untersucht. Wenn Silberhalogenid-Sole durch Thoriumnitrat-L?sungen koaguliert werden, bilden sich zwei Koagulationsmaxima (II und IV, Abb. 1). Bei sehr niedrigen Konzentrationen des Thoriumnitrats koaguliert das Thorium-Ion (oder Komplex) die negativen Silberhalogenid-Sole, w?hrend bei h?heren Thoriumnitrat-Konzentrationen die ungeladenen Sole durch die NitratIonen koaguliert werden. Zwischen den zwei Maxima besteht ein weites Gebiet der stabilen umgeladenen Sole (III). Unter dem Zusatz von konstanten Mengen des Kaliumnitrats wird in diesem Gebiet ein neues (drittes) Maximum gebildet (Abb. 2–5), das auch als Koagulationsmaximum identifiziert wurde. Es wird angenommen, da? dieses Maximum wieder eine Koagulation der umgeladenen Silberhalogenid-Sole durch Nitrat-Ionen darstellt. Das Auftreten von zwei Koagulationsmaxima, verursacht durch Nitrat-Ionen, wird durch die verschiedenen Ladungsdichten an Solteilchen in Gebieten der Thoriumnitrat-Konzentrationen, in denen Maxima erscheinen, erkl?rt. Die M?glichkeit eines Koagulationseffektes der komplexen Ionen zwischen Thorium und Nitrat wurde ausgeschlossen, da die Gleichgewichtskonstante solcher Komplexe ziemlich niedrig ist. In Anwesenheit von Kaliumsulfat sieht die Koagulationskurve für Silberhalogenid Sole sehr unterschiedlich aus (Abb. 6–8). In den mit Salpeters?ure (0,001N) versetzten Solen erscheint nur ein Maximum bei ziemlich hohen Thoriumnitrat-Konzentrationen [∼ 10⁻³ N Th (NO₃)₄], wobei die Solteilchen noch immer negativ sind. Da Thorium- und Sulfat-Ionen sehr stabile Ionen-Komplexe bilden, die eine niedrigere Valenz aufweisen, kann das Maximum als Folge der Koagulationseffekte solcher Komplexe an die Silberhalogenid-Sole angesehen werden. In neutralen L?sungen zeigt sich neben dem beschriebenen Maximum noch ein anderes Maximum bei niedrigerer Thoriumnitrat-Konzentration. Dieses Maximum, hervorgerufen durch die hydrolysierten Thorium-Ionen, scheint das „normale“ Koagulationsmaximum zu sein. Dieantagonistischen Effekte des Salzpaares Th (NO₃)₄-K₂SO₄ bei der Koagulation der Silberhalogenide wurden diskutiert, und es wurde geschlossen, da? die gro?en Effekte, die wiederholt ver?ffentlicht worden waren, sehr schwer nur durch die elektrostatischen Anziehungen zwischen den Ionen erkl?rt werden k?nnen. Die Komplexbildung zwischen Thorium- und Sulfat-Ionen wird für den sogenannten antagonistischen Effekt in diesem Falle als verantwortlich angesehen.

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Supported in part by U.S. Atomic Energy Commission Contract No. AT (30-1)-1801.     

Effect of transition metal chloride additives on the radiolysis of aqueous sodium nitrate

Radiolysis of aqueous sodium nitrate solution was studied as a function of concentration in the range 10^–4M to 1M NaNO₃. The radiolytic yield of nitrite was found to be linear with dose and concentration. The effect of transition metal chloride additives on the radiolysis of 0.01M NaNO₃ resulted in higher and lower yields of nitrite in the presence of cobalt and nickel chlorides, respectively, than that obtained in the pure nitrate system. The reduction of nitrate to nitrite is totally quenched even at very low concentration of copper chloride in the binary mixture. The results are explained on the basis of oxidizing and reducing properties of transition metal ions.     

Novel Thorium Membrane Sensors with Anionic Response Based on Trioctylphosphine Oxide and Toluate Ionophores

Two novel potentiometric polymeric membrane sensors for rapid and accurate determination of thorium are described. These are based on the use of trioctylphosphine oxide (TOPO) and thorium toluate (Th‐TA) as ionophores dispersed in poly(vinyl chloride) matrix membranes plasticized with nitrophenyloctyl ether. In strong nitric acid medium, Th(IV) nitrate is converted into [Th(NO₃)₆]^2? complex and sensed as anionic divalent ion which exclude most cationic effect. Validation of the assay methods using the quality assurance standards (linearity range, accuracy, precision, within‐day variability, between‐day‐repeatability, lower detection limit and sensitivity) reveals excellent performance characteristics of both sensors. The sensors exhibit near‐Nernstian response for 1.0×10^?6–1.0×10^?1 M Th over the pH range 2.5–4.5. Calibration slopes of ?32.3±0.3 and ?27.2±0.2 mV/decade, precision of ±0.5 and ±0.8% and accuracy of 98.8±0.9 and 97.9±0.7% are obtained with TOPO and Th‐TA based sensors, respectively. Negligible interferences are caused by most interfering mono‐, di‐, tri‐, tetra‐, penta‐, and hexa‐valent elements commonly associated with thorium in naturally occurring minerals and ores. High concentrations of Cl^?, F^?, SO₄^2?, and NO₃^? ions have no diverse effect. Complete removal of the effect of the interferents in complex matrices is achieved by retention of [Th(NO₃)₆]^2? complex from 5 M nitric acid/methanol mixture (1 : 9 v/v) on a strong anion exchanger, washing out the cationic interferents followed by stripping off thorium anion complex and measurements. Both sensors are used for determining thorium in certified thorium ore samples (20–120 mg Th/kg) and some naturally occurring ores (200–600 mg Th/kg). The results obtained agree fairly well with the certified labeled values or the data obtained using X‐ray fluorescence spectrometry     

Separation of zirconium and hafnium from early actinides and rare earth elements with eichrom’s pb resin in HCl

The separation of zirconium and hafnium isotopes from the early actinides and rare earth elements (REE) with Eichrom’s Pb resin has been studied. Batch studies were performed to characterize the behavior of actinium, thorium, zirconium, hafnium, lutetium, and yttrium on Pb resin from HCl solutions (0.001 M to 11 M). The early actinides and REE had no affinity for the resin at any concentration of HCl, but zirconium and hafnium showed a moderate uptake at high concentrations of HCl with a maximum extraction at 11 M HCl. Several column separations were tested, including with only tracer isotopes and with mass. Rapid, simple separations of zirconium from actinium, thorium, protactinium, and the REE with high yields and low elution volumes are presented with applications for tracer isotope production and fission product separations. The resin is less suitable for hafnium separations as hafnium tends to bleed off the resin even at high concentrations of HCl.

     

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%).     

Component activities in the system thorium nitrate-nitric acid-water at 25°C

The equilibrium composition of the vapor above thorium nitrate-nitric acid-water mixtures has been studied as a function of the concentrations of thorium nitrate and nitric acid using a transpiration technique. At 25°C, the thorium nitrate concentrations m _T ranged from 0.1 to 2.5 molal and the nitric acid concentrations m _N from 0.3 to 25 modal. The vapor pressure of the nitric acid was found to increase with increasing thorium nitrate concentration for a constant molality of nitric acid in aqueous solution. At constant m _T , the nitric acid vapor pressure was particularly enhanced at low nitric acid concentrations. The water vapor pressures decreased regularly with increasing concentrations of both nitric acid and thorium nitrate. The experimental data were fitted to Scatchard's ion-component model, and to empirical multiparameter functions. From the fitting parameters, and available literature data for the nitric acid-water and thorium nitrate-water systems at 25°C, expressions were calculated for the variation of water and thorium nitrate activities, as functions of the nitric acid and thorium nitrate concentrations, using the Gibbs-Duhem equation. Calculated values for the thorium nitrate activities were strongly dependent on the form of the function originally used to fit the vapor pressure data.Issued as AECL-7461.     

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.     

Hydrogen-Bonded Dimers in Dipyrrinones and Acyldipyrrinones

Summary.  A crystal structure determination of the 9-acyl-dipyrrinone 9-butanoyl-2,3,7,8-tetramethyl-(10H)-dipyrrin-1-one indicates the presence of intermolecularly hydrogen-bonded dimers; however, in CHCl₃ solution the pigment is monomeric as determined by vapor pressure osmometry measurements. Lacking an alkyl group at C(8), the 9-acyl-dipyrrinone exhibits only a weak tendency to form dimers in CHCl₃ (K _A ∼ 60 M ⁻¹) as determined by analysis of variable temperature ¹H NMR data. In contrast, when the 9-acyl group is replaced by formyl or when the acyl group is fixed in a syn orientation to the pyrrole NH, the dipyrrinone is strongly prone to dimerization in CHCl₃. Received August 22, 2000. Accepted September 5, 2000     

The Influence of Ionic Strength on Yttrium and Rare Earth Element Complexation by Fluoride Ions in NaClO<Subscript>4</Subscript>, NaNO<Subscript>3</Subscript> and NaCl Solutions at 25 °C

Stability constants of the form _F β ₁(M)=[MF²⁺][M³⁺]⁻¹[F⁻]⁻¹ (where [MF²⁺] represents the concentration of a yttrium or a rare earth element (YREE) complex, [M³⁺] is the free YREE ion concentration, and [F⁻] is the free fluoride ion concentration) were determined by direct potentiometry in NaNO₃ and NaCl solutions. The patterns of log_{10  F} β ₁(M) in NaNO₃ and NaCl solutions very closely resemble stability constant patterns obtained previously in NaClO₄. For a given YREE, stability constants obtained in NaClO₄ were similar to, but consistently larger than _F β ₁(M) values obtained in NaNO₃ which, in turn, were larger than formation constants obtained in NaCl. Stability constants for formation of nitrate and chloride complexes ( and _Cl β ₁(M)=[MCl²⁺][M³⁺]⁻¹[Cl⁻]⁻¹) derived from _F β ₁(M) data exhibited ionic strength dependencies generally similar to those of _F β ₁(M). However, in contrast to the somewhat complex pattern obtained for _F β ₁(M) across the fifteen member YREE series, no patterns were observed for nitrate and chloride complexation constants: neither nor _Cl β ₁(M) showed discernable variations across the suite of YREEs. Nitrate and chloride formation constants at 25 °C and zero ionic strength were estimated as log₁₀  and log_{10  Cl} β ₁^o(M)=0.71±0.05. Although these constants are identical within experimental uncertainty, the distinct ionic strength dependencies of and _Cl β ₁(M) produced larger differences in the two stability constants with increasing ionic strength whereby _Cl β ₁(M) was uniformly larger than .     

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.     

Selective solvent extraction of chromium(VI) using 2-hexylpyridine

The extraction behaviour of trace and macroamounts of chromium(VI) from different mineral acid solutions by 2-hexylpyridine in chloroform has been investigated. In the chloride system, the extracted species is apparently (HPyH⁺)₂ (Cr₂O₇)²⁻ or HPy⁺(HCrO ₄ ⁻ ) for macro and trace amounts of chromium(VI), respectively. Among the common anions chloride and sulphate have little effect on extraction up to 1M concentration, while in the case of nitrate there is a continuous decrease in the extraction with the increase of salt concentration in the aqueous phase. The effect of ascorbate, acetate, citrate, oxalate, thiosulphate, thiocyanate ions on the extraction from 1M HCl was also examined. Separation factors of several elements relative to chromium(VI) have been described and the separation of chromium(IV) from a large number of elements has been achieved.     

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.     

Fourier transform infrared determination of caffeine in roasted coffee samples

A new procedure has been developed for the FT-IR determination of caffeine in roasted coffee samples. The method involves wetting the coffee samples with a 0.25 M aqueous NH₃ solution, extracting the caffeine with CHCl₃, and measuring absorbance at 1659 cm^–1 using a baseline established between 1900 and 830 cm^–1. The procedure proposed is fast, only requiring a total extraction time of 16 min for each sample, and provides a drastic reduction of the organic solvent consumed, from the 200 mL diethyl ether and 50 mL CHCl₃ required for each sample by the reference chromatographic UV-spectrometric determination to only 5 mL CHCl₃. The method provides a limit of detection of the order of 3 mg L^–1 caffeine and a relative standard deviation of 0.4% for 3 independent analyses of a sample containing 18.6%mg/g caffeine. The accuracy of the FT-IR procedure was evaluated from recovery experiments on spiked samples providing values from 94.4 to 100.1% and from the comparison of results found for a series of commercial samples, by both FT-IR and the official reference procedure. Received: 9 July 1999 / Revised: 23 September 1999 / /Accepted: 24 September 1999