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.     

Separation of scandium(III) and yttrium(III) by tris(2-ethylhexyl)phosphate (TEHP)

Tris(2-ethylhexyl)phosphate is proposed as an extractant for scandium(III) and yttrium(III) from salicylate media. The optimum extraction conditions are evaluated and described. The method permits mutual separation of scandium(III) and yttrium(III) and can be used for the separation and determination of scandium(III) and yttrium(III) from binary and multicomponent mixtures.     

Tris(2-ethylhexyl)phosphate as an extractant for trivalent gallium, indium and thallium

A systematic study of solvent extraction behaviour of gallium(III), indium(III) and thallium(III) with tris(2-ethylhexyl)phosphate from salicylate media has been undertaken and a scheme for their separation is proposed. The optimum extraction conditions are evaluated and described. The method is applicable to the analysis of standard aluminium and aluminium alloys samples. The results obtained are reproducible and accurate.     

Liquid-liquid distribution studies of thorium salicylate with tris-(2-ethylhexyl)phosphate

A method is proposed for the extraction of thorium(IV) from salicylate media using tris-(2-ethylhexyl)phosphate dissolved in toluene as an extractant. The optimum conditions were evaluated from a critical study of pH, salicylate concentration, extractant concentration, period of equilibration and diluent. The method permits the separation of thorium from the associated elements and is applicable to the analysis of monazite sand. The method is precise, accurate, fast and selective.     

Separation of molybdenum from tungsten with di(2-ethylhexyl)-phosphoric acid ac extractant

The use of di(2-ethylhexyl)phosphoric acid (HDEHP) as an extractant for the separation of molybdenum from tungsten was examined with the help of molybdenum-99 and tungsten-187 as radiotracers. Effective separation was obtained when the aqueous phase contained phosphoric acid at pH 0.8–2 or pH 3–3.5, depending on the amounts of metal. The method is applicable to both tracer and milligram amounts of molybdenum. The structure of the extracted species was examined by infrared spectroscopy.     

Tracer scale solvent extraction separation of tantalum from niobium using di-(2-ethylhexyl)-phosphoric acid as extractant

A simple solvent extraction procedure for the efficient separation of the radioactive tracers⁹⁵Nb and¹⁸²Ta from each other in a mixture using di-(2-ethylhexyl)phosphoric acid (HDEHP) as extractant is described. Tantalum was found to be quantitatively extracted from an aqueous madium, which is 1.6N in HCl and 10^?2 M in oxalic acid, with a HDEHP solution of 0.1 M concentration. Extractabilities of both niobium and tantalum in mineral acids like HCl, H₂SO₄ and HNO₃ and in some organic acids like oxalic, citric, etc., in HDEHP under the experimental conditions were also studied. The reliability of the separation procedure was verified further by γ-ray spectrometry.     

Separation of thorium from uranium ore

Thorium-230 has many research applications, but there is not a commercial source of this isotope. However, since ²³⁰Th is part of the ²³⁸U decay chain, it can be separated from naturally occurring uranium. In this work, a novel procedure was developed to separate thorium from uranium ore, consisting of leaching, liquid–liquid extraction, precipitations and ion exchange chromatography. The final product was 91.32?±?0.77 mg of thorium with a purity of 99.5?±?1.2 wt%. Of that, 7.65?±?0.10 mg was ²³⁰Th and the remainder ²³²Th. The total yield of ²³⁰Th was 71.1?±?5.4%. Ways to improve the yield by further processing the back-extraction solution are suggested.

     

Tris(2-ethylhexyl)phosphate as an extractant for quadrivalent tin,with subsequent determination with pyrocatechol violet in alloy samples

The solvent extraction of tin(IV) from chloride media withtris(2-ethylhexyl)phosphate is presented. Tin(IV) is extracted quantitatively from 2.75–3.20 mol dm^–3 hydrochloric acid using 6.38–6.91 mol dm^–3 tris(2-ethyl-hexyl)phosphate dissolved in toluene as an extractant. After back-extraction of tin(IV) with water from thetris(2-ethylhexyl)phosphate phase, it is estimated spectrophotometrically following complexation with pyrocatechol violet. The recommended range for determination of tin(IV) is 10–100 g. The probable extracted species is SnCl₄·2TEHP. The method is applicable to the analysis of alloy samples with a detection limit of 0.4 g/ml (for 10 g of tin) and a relative standard deviation between 0.21–0.32%.     

Bis(2-ethylhexyl)sulfoxide as an extractant for americium(III) from aqueous nitrate media

Solven extraction separation of americium(III) from dilute aqueous nitrate media into n-dodecane by bis(2-ethylhexyl)sulfoxide (BESO) has been investigated over a wide range of experimentgal conditioins. Very poor extractablity of Am(III), necessitated the use of calcium nitrate as the salting-out agent. Effects of certain variables such as acidity, extractant concentration, salting-out agent concentration, organic diluents on the metal extraction by BESO have been examined in detail. By increasing the concentration of BESO in organic phase or calcium nitrate in aqueous phase, nearly quantitative extraction of americium even from moderate acidity is accomplished. Slope analyses applied to Am(III) distribution experiments from acidic nitrate solutions indicate predominant formation of the risolvated organic phase complex, Am(NO₃)₃)·3BESO for which equilibrium constant is found to be, log K_x=1.99. Extraction behavior of Am(III) has also been evlauated in the presence of several water-miscible polar organic solvents to stuy their possible synergistic effects on its extraction. Extractability of americium increased 5 to 10-fold withi increasing conentration of some of these additives, with maximum enhancement being observed in the presence of acetone or acetonitrile. Recovery of BESO from loaded americium is easily obtained using dilute nitric acid as the strippant.     

Di(2-ethylhexyl)sulfoxide as an extractant for plutonium(IV) from nitric acid medium

The liquid-liquid extraction behavior of plutonium(IV) from aqueous nitric acid media into n-dodecane by di(2-ethylhexyl)sulfoxide (DEHSO) was investigated over a wide range of conditions. Optimum-parameters such as the aqueous phase acidity, reagent and metal concentrations, etc., were established for efficient extraction-separation of tracer as well as macro levels of plutonium. It was found that the extraction increased with increasing nitric acid concentration up to 6M HNO₃ and then decreased. Extraction also increased with increasing extractant concentration. After loading of the organic phase with 2 to 50 mg/ml of U(VI), extractability of Pu(IV) became considerably lower. Recovery of Pu(IV) from the organic phase was accomplished using dilute uranium(IV) nitrate as the strippant.     

Preparation of high-purity thorium by solvent extraction with di-(2-ethylhexyl) 2-ethylhexyl phosphonate

The extraction behavior of thorium(IV) by di-(2-ethylhexyl) 2-ethylhexyl phosphonate (DEHEHP, B) from nitric acid media has been investigated. The influence factors including the concentration of HNO₃, salting-out reagents, temperature, the concentration of metal ions and DEHEHP have been examined systematically. A possible extraction mechanism is proposed and the extracted species as Th(NO₃)₄·2B _(o) is confirmed by the slope analysis method. The extraction equilibrium constants (K _ex) and thermodynamic parameters (ΔG, ΔH and ΔS) were calculated under the present experimental conditions. DEHEHP shows a high selectivity of thorium(IV) over rare earths(III). Stripping study indicates that thorium can be completely stripped by distilled water from the Th-loaded DEHEHP. Furthermore, a solvent extraction process including six extraction stages, six scrubbing stages, and six stripping stages was designed for the preparation of highly pure thorium from thorium concentrate with DEHEHP as extractant in laboratory scale, and finally thorium product can be obtained with a purity of 99.999 % and a yield of 98 %.     

Separation studies of molybdenum(VI) and rhenium(VII) using TPPO as an extractant

A simple, rapid and reproducible method for the extractive separation of molybdenum(VI) and rhenium(VII) is proposed using triphenylphosphine oxide (TPPO) dissolved in toluene as an extractant. The extractions are carried out from the hydrochloric and hydrobromic acid medium. The extraction of molybdenum is quantitative from 2.54-3.10 M hydrochloric acid and from 3.76-3.98 M hydrobromic acid, and that of rhenium is from 6.78-7.91 M hydrochloric acid. The probable nature of the extractable species is established using log distribution ratio-log concentration plots. The method permits mutual separation of molybdenum(VI) and rhenium(VII) and is applicable for the analysis of alloys and pharmaceutical sample. The detection limits for molybdenum(VI) and rhenium(VII) are 0.8 ppm and 4 ppm respectively.     

Solvent extraction separation of tantalum from niobium on macro scale using di(2-ethylhexyl) phosphoric acid as extractant

A solvent extraction procedure for the separation of niobium and tantalum has been developed. The method consists of extracting tantalum from its aqueous mixture with niobium, with the help of di(2-ethylhexyl)phosphoric acid (HDEHP) in n-heptane. The aqueous feed consists of niobium and tantalum in an aqueous medium containing hydrochloric and oxalic acids. The concentrations of niobium and tantalum were raised to 1 mg/ml in the aqueous solution. The extraction efficiency of tantalum under these conditions was found to be 85%. Effects of chloride and oxalate ions as well as those of the concentration of HDEHP on the extraction efficiency were studied and discussed in detail.     

Separation of antimony from uranium using zirconium phosphate

Summary The distribution behaviour of antimony and uranium between zirconium phosphate and hydrochloric acid solutions of different concentrations has been determined. The effect of organic solvent addition to the aqueous phase on the distribution data has been investigated. In all cases, the separation factors are evaluated and discussed. The best separation factor was achieved using 1M HCl over all organic-aqueous solvent mixtures. Based on these findings, a procedure has been developed for the separation of antimony from uranium using a Chromatographic column loaded with zirconium phosphate and 1M HCl as eluant.

---

Zusammenfassung Das Verteilungsverhalten von Antimon und Uran zwischen Zirkonium-phosphat und Salzsäure verschiedener Konzentration wurde bestimmt. Der Einfluß zugesetzten organischen Lösungsmittels auf die Verteilungsdaten wurde untersucht. Die besten Trennungsergebnisse wurden mit 1-n Salzsäure ohne jeden organischen Zusatz erzielt. Auf dieser Grundlage wurde ein Verfahren ausgearbeitet, um mit Hilfe einer mit Zirkoniumphosphat beladenen chromatographischen Säule und mit 1-n Salzsäure als Elutionsmittel Antimon von Uran zu trennen.

     

Emulsion liquid membrane extraction of Ni(II) and Co(II) from acidic chloride solutions using bis-(2-ethylhexyl) phosphoric acid as extractant

An emulsion liquid membrane process using bis-(2-ethylhexyl) phosphoric acid (D2EHPA) to extract and separate Ni(II) and Co(II) from acidic chloride solutions is described. Liquid membrane consists of a diluent, a surfactant (Span 80), and an extractant (D2EHPA). Hydrochloric acid was used as the stripping solution. The important parameters governing the permeation of nickel and their effect on the separation process have been studied. These parameters are stirring speed, feed phase pH, surfactant concentration, extractant concentration, stripping phase concentration, phase ratio, initial concentration of metal, and treatment ratio. The optimum conditions have been determined. The separation factors of Ni(II) with respect to Co(II), based on initial feed concentration, have been experimentally determined. Furthermore, the extraction selectivity for Co(II) over Ni(II) has been improved by using D2EHPA during the initial minutes.     

Synthesis and characterization of N,N,N',N'-tetrabutylsuccinamide as extractant for uranium(VI) and thorium(IV) ions from nitric acid solution

Synthesis and characterization of N,N,N',N'-tetrabutylsuccinamide (TBSA)was carried out and used for the extraction of U(VI) and Th(IV) from nitricacid solutions. Toluene was found to be the most suitable diluent for TBSAcompared with the other diluents tested. Extraction distribution ratios (D)of U(VI) and Th(IV) have been studied as a function of aqueous HNO 3 concentrations,NO₃ – ion concentration, TBSA concentration and temperature.The results obtained indicated that U(VI) and Th(IV) are mainly extractedas UO₂ (NO₃ ) ₂ . ₂TBSA and Th(NO₃ ) ₄ . TBSA, respectively, and the IR spectra of the extractedspecies have been investigated. The values of thermodynamic functions havebeen calculated. Back-extraction of U(VI) and Th(IV) from organic phases wasalso studied.     

Characterization and application of sodium di(2-ethylhexyl) sulfosuccinate and sodium di(2-ethylhexyl) phosphate surfactants as pseudostationary phases in micellar electrokinetic chromatography

Sodium di(2-ethylhexyl) sulfosuccinate (DOSS) and sodium di(2-ethylhexyl) phosphate (NaDEHP) surfactants, with double alkyl chains and negatively charged headgroups, were characterized using fluorescence quenching, densitometry, and tensiometry techniques to determine their aggregation number, partial specific volume, and critical aggregation concentration. These two surfactants were then applied as pseudostationary phases in micellar electrokinetic chromatography (MEKC) for separations of alkyl phenyl ketones. The aggregation number of NaDEHP was found to be more than two-fold higher than that of DOSS. The partial specific volumes of NaDEHP and DOSS were found to be 0.9003 and 0.8371 mL/g, respectively. The critical aggregation concentrations are 5.12 and 1.80 mM for NaDEHP and DOSS, respectively. The DOSS surfactant provided a wider separation window and had a greater hydrophobic environment than the NaDEHP surfactant under the MEKC experimental conditions studied.     

Recovery and pre-concentration of americium (III) from dilute acid solutions using an emulsion liquid membrane containing di-2-ethylhexyl phosphoric acid (D2EHPA) as extractant

Radiochemical results of U isotopes (²³⁴U, ²³⁵U and ²³⁸U) and their activity ratios are reported for well waters as local sources of drinking waters collected from the ten settlements around the Semipalatinsk Nuclear Test Site (SNTS), Kazakhstan. The results show that ²³⁸U varies widely from 3.6 to 356 mBq/L (0.3–28.7 μg/L), with a factor of about 100. The ²³⁸U concentrations in some water samples from Dolon, Tailan, Sarzhal and Karaul settlements are comparable to or higher than the World Health Organization’s restrictive proposed guideline of 15 μg (U)/L. The ²³⁴U/²³⁸U activity ratios in the measured water samples are higher than 1, and vary between 1.1 and 7.9, being mostly from 1.5 to 3. The measured ²³⁵U/²³⁸U activity ratios are around 0.046, indicating that U in these well waters is of natural origin. It is probable that the elevated concentration of ²³⁸U found in some settlements around the SNTS is not due to the close-in fallout from nuclear explosions at the SNTS, but rather to the intensive weathering of rocks including U there. The calculated effective doses to adults resulting from consumption of the investigated waters are in the range 1.0–18.7 μSv/y. Those doses are lower than WHO and IAEA reference value (100 μSv/y) for drinking water.     

Separation and spectrophotometric determination of thorium contained in uranium concentrate

A method for the determination of thorium in uranium concentrate by spectrophotometry with Arsenazo III has been developed. Preliminary solvent extraction procedures were used to eliminate interfering species. Samples were dissolved in nitric, perchloric and sulfuric acid and the uranium extracted from the solution using tri-octylamine. The aqueous layer was evaporated to dryness and the residue re-dissolved with hydrochloric acid, thorium was extracted by tri-n-octyl phosphine oxide and stripped with oxalic acid. For a typical uranium concentrate produced from the phosphate rock of Itataia, Brazil, concentrations of thorium as low as 5 g·g^-1 can be determined.