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.     

Solvent extraction of pertechnetate with TBP from perchloric acid solution

Solvent extraction mechanism of pertechnetic acid with TBP from perchloric acid solutions is discussed. When cyclohexane is used as a diluent of TBP, perchloric acid can be extracted in the form of HClO₄(TBP)₂ into the organic phase. The TBP extraction of pertechnetic acid competes with perchloric acid and its equilibria are expressed as follows: HTcO₄+3TBPHTcO₄(TBP)₃ and HTcO₄(TBP)₃+TBPHTcO₄(TBP)₄.     

Liquid-liquid extraction of molybdenum(VI) and uranium(VI) by LIX 622

The order of extraction of Mo(VI) from 1M acid solutions by 5% (v/v) LIX 622 (HL) in benzene is HCl>HNO₃>HClO₄>H₂SO₄, and extraction decreases with increasing concentration of HCl and H₂SO₄, and increases slightly with increasing concentration of HNO₃ and HClO₄. The extracted species is shown to be MoO₂L₂ as established by IR data of organic extracts and the extracted species in the solid form. Extraction is almost quantitative at and above 10% LIX 622, and is found to be independent of [Mo(VI)] in the range of 10^–4 to 10^–3 M. The diluents CCl₄, CHCl₃ and C₆H₆ are found to be superior to solvents of high dielectric constant for extraction of Mo(VI). Extraction of uranium(VI) by 10% (v/v) LIX 622 in benzene was found to increase with increasing equilibrium pH (3.0 to 6.0), and becomes quantitative at pH 5.9. Tributyl phosphate acts as a modifier up to 2% (v/v). Thorium(IV) is almost not extracted by LIX 622 or its mixture. Separation of Mo(VI) and U(VI) is feasible.     

Separation of europium and thulium from mixed KI−H2SO4 solutions

The extraction of Tm with HDEHP from H₂SO₄, HCl and HBr is inversely proportional to the third power of the hydrogen ion concentration while the extraction is small with HDEHP, LA-2 and TBP from binary mixtures of acids. The extraction of both Eu and Tm with HDEHP from KI solutions decreases in the presence of small concentrations of H₂SO₄. The decrease is sharper in case of Eu leading to high separation factors between Eu and Tm from KI?H₂SO₄ mixtures.     

Separation of neptunium, plutonium, americium and curium from uranium with di-(2-ethylhexyl)-phosphoric acid (HDEHP) for radiometric and ICP-MS analysis

The possibility of using di-(2-ethylhexyl)-phosphoric acid (HDEHP) in solvent extraction for the separation of neptunium, plutonium, americium and curium from large amounts of uranium was studied. Neptunium, plutonium, americium and curium (as well as uranium) were extracted from HNO₃, whereafter americium and curium were back-extracted with 5M HNO₃. Thereafter was neptunium back-extracted in 1M HNO₃ containing hydroxylamine hydronitrate. Finally, plutonium was back-extracted in 3M HCl containing Ti(III). The method separates²³⁸Pu from²⁴¹Am for α-spectroscopy. For ICP-MS analysis, the interferences from²³⁸U are eliminated: tailing from²³⁸U, for analysis of²³⁷Np, and the interference of²³⁸UH⁺ for analysis of²³⁹Pu. The method has been used for the analysis of actinides in samples from a spent nuclear fuel leaching and radionuclide transport experiment.     

Radiochemical separation of99Mo from natural uranium irradiated with thermal neutrons

⁹⁹Mo was separated from uranium and insoluble fission product hydroxides. More than 98% of⁹⁹Mo radioactivity was extracted with bis (2-ethylhexyl)phosphoric acid. The organic phase was washed and⁹⁹Mo was back-extracted from the organic phase with NH₄OH solution. The percent recovery from the organic phase was 91% and the purity of⁹⁹Mo was more than 99%. Pure^99mTc was also extracted from the organic phase with a saline solution. Reversed-phase partition chromatography was used for the purification of⁹⁹Mo from¹³¹I and other fission products (10% HDEHP on kieselguhr bed).¹³¹I and other isotopes were quantitatively eluted with 0.1M H₂SO₄,⁹⁹Mo was eluted using a mixture of 0.5 M HCl and 30% H₂O₂.     

Separation of metal halide pairs using Amberlite LA-2 and tri-N-butyl phosphate

A systematic study was performed on the extraction and separation of cadmium from iron halides in pure halo-acid solutions and their mixtures with H₂SO₄ and H₃PO₄. As solvents Amberlite LA-2, TBP, nitrobenzene and HDEHP were used. Recommended separation media for the amine are 2M HCl, 1M HBr, 1.12M HCl?2M H₂SO₄, 0.64M HBr?2M H₂SO₄, 1.12M HCl?4M H₃PO₄ 0.64M HBr?7M H₃PO₄ and for TBP the medium 0.64M HBr?4M H₃PO₄ is the only suitable condition.     

Desorption of99Mo from spent99Mo/99mTc generator

A simple method for desorption and purification of⁹⁹Mo from spent⁹⁹Mo/^99mTc generators is described. The alumina column was washed successively with 0.9% saline water, 35% H₂O₂, and then the⁹⁹Mo was eluted with 2M NH₄OH. Ammonia and residual H₂O₂ were removed by heating the eluate. Finally,⁹⁹Mo solution was passed through a 0.2 m membrane filter to remove precipitated aluminium hydroxide.     

Extraction of Am(III) from different acid media by di-2-ethyl hexyl phosphoric acid containing phosphorous pentoxide

The extraction of Am(III) from nitric, hydrochloric, oxalic, phosphoric and hydrofluoric acids was studied using 0.4F di-2-ethyl hexyl phosphoric acid (HDEHP) containing 0.1M phosphorous pentoxide (P₂O₅) in dodecane/xylene. The extraction with pure 0.4F HDEHP was found to be negligible from all the media studied. However, the presence of a small amount of P₂O₅ in it increased the extraction substantially. The distribution ratios of Am(III) obtained for HDEHP - P₂O₅ mixture 3M nitric acid containing different concentrations of oxalic acid/phosphoric acid/hydrofluoric acid are in the order of 200-250. The same for 3M hydrochloric acid is very high (800). These distribution ratios are sufficiently high for the quantitative extraction of Am(III) from all the acid media studied. Different reagents such as ammonium oxalate, sodium oxalate, oxalic acid, hydrofluoric acid, sodium carbonate and potassium sulphate were explored for the back extraction of Am(III) from 0.4F HDEHP + 0.1M P₂O₅ in dodecane/xylene. Of these, 0.35M ammonium oxalate and 1M sodium carbonate were found to be most suitable. The back extraction of Am(III) was also attempted with water and 1M H₂SO₄, HNO₃, HClO₄ and HCl solutions after allowing the extracted organics to degrade on its own. It was found that more than 90% of Am could be back extracted with these acids. Using this method more than 90% of Am(III) was recovered from nitric acid solutions containing calcium and fluoride ions.     

Extraction and separation of60Co and65Zn halides from H2SO4 with TBP and amberlite LA-2

A systematic study is presented on the extraction of⁶⁰Co and⁶⁵Zn bromides and chlorides from H₂SO₄ with tri-n-butyl phosphate (TBP) and Amberlite LA-2. It has been found that the presence of a little HBr or HCl enhances the extraction of the two isotopes with both solvents. The extractions of⁶⁰Co and⁶⁵Zn have been studied as functions of the acidity (HBr, HCl or H₂SO₄) in the aqueous phase, and of the diluent and solvent concentrations in the organic phase. The presence of water-miscible alcohols or acetone enhances extraction. A suggested extraction mechanism is presented in the light of the obtained results.     

Cyclic transport of Fe3+ As H[FeCl4] and H[FeBr4] through a dibutyl ether-benzene membrane

Cyclic transport of Fe³⁺ as H[FeX₄], where X is Cl or Br, across solvent-type liquid membranes has been demonstrated. H[FeCl₄] was transported from HCl into HBr across a dibutyl ether—benzene mixture. In HBr the transported species reacted to H[FeBr₄], which moved out to the HCl side against the concentration gradient of Fe³⁺. On the HCl side it was reconverted into H[FeCl₄]. This continued till equilibrium was achieved. Likewise, Fe³⁺, present as H[FeBr₄] in HBr, migrated from HBr into HCl and then back to HBr across the same membrane.     

Cerium isotope partition in HNO3/TBP or HDEHP extraction systems

The^142/140Ce unit separation factors (q) for cerium(III)-cerium(IV) exchange reaction in an extraction system containing Ce(IV) in tri-n-butyl phosphate (TBP) or di(2-ethylhexyl) phosphoric acid (HDEHP) and Ce(III) in nitric acid were determined. The value of q was found to be 1.00054±0.00012 (2) in 6M HNO₃/TBP and 1.00078±0.00028 in 6M HNO₃/HDEHP extraction systems. The dehydration and complex formation processes and their contribution to reduced partition function ratios (RPFR's) are discussed.     

Study of the suitability of HNO<Subscript>3</Subscript> and HCl as extracting agents of mercury species in soils from cinnabar mines

The aim of this study was to compare the influence and feasibility of two common extracting agents (50% v/v HCl and 50% v/v HNO₃) on the leaching of Hg from soils. The solubility of a number of Hg species in each acid solution was evaluated under selected conditions. Most species were quantitatively dissolved in both acids with the exception of HgS. The application of both acid solutions to a soil sample from the Almaden mining area provided different recoveries of Hg: about 5% in 50% v/v HNO₃ and 50% in 50% v/v HCl. The following experiments were designed and developed in order to evaluate the matrix influence on HgS solubility and leaching: (1) study of the solubility of HgS in the presence of different potential interfering compounds such as FeCl₃, KCl, KI, Fe₂O₃, CuSO₄, FeSO₄, MnO₂ and NaNO₃; (2) study of the recovery of HgS spiked in soil samples; (3) study of the extraction process in soil samples spiked with the critical interfering compounds. Results showed the existence of a greater matrix influence with the HCl solution, since much higher Hg recoveries were obtained with this reagent. In addition, the presence of nitrates and Mn oxides drastically promotes the solubility of HgS in an HCl solution. On the other hand, halide compounds drastically enhanced the extractability of Hg in the HNO₃ and they must be considered as potential interfering compounds when this acid solution is used as extracting agent. In summary, neither acid is totally free of matrix effects from common soil constituents; conclusions about mercury mobility resulting from the general application of these extraction procedures must therefore be made with caution.     

Solvent extraction of hafnium(IV) by TBP and topo from acidic organic-aqueous solutions

Tracer concentrations of Hf(IV) were extracted by 60% TBP solution in benzene from 5M HClO₄, 5M HCl, 6M HNO₃ and 8M H₂SO₄ solutions, and by 1·10^?4 M TOPO solution in benzene from 2M HClO₄ and 2M HCl solutions in the presence of a variety of organic solvents miscible with the aqueous phase. Whereas for TBP these solvents caused an increase of HF(IV) extraction, an opposite effect was observed for TOPO. The results were discussed from the point of view of various solute-solvent and solvent-solvent interactions.     

Extraction of pertechnetate by triphenyltin chloride and trioctyltin chloride

The extraction of pertechnetate in form of ionogene associates with triphenyltin and trioctyltin cations into chloroform, benzene, toluene and nitrobenzene was studied. As aqucous phases solutions of^99mTcO ₄ ^? in deionized water and in diluted solutions of NaCl, HCl, NaNO₃, HNO₃ NaClO₄, HClO₄ and NaOH were used. Concerning the organic phases, at the use of triphenyltin chloride the extractibility of pertechnetate increases in the sequence: toluene «chloroform, benzene nitrobenzene and approximately in the sequence: NaOH<NaCl, HCl<NaNO₃<H₂O<NaClO₄ concerning aqueous phases. For trioctyltin chloride in chloroform the extractibility of TcO ₄ ^? increases approximately in the sequence of aqueous phases: NaOH<HCl, NaNO₃, NaClO₄, NaCl«H₂O and in nitobenzene in the sequence NaOH<NaClO₄<HCl<NaNO₃, NaCl«H₂O. The extractibility for trioctyltin chloride is in general slightly lower as compared with triphenyltin chloride. The results of the extraction are presented in the form of graphical plots of technetium distribution ratio (D _Te′ logD _Tc) or extraction yield (E _Tc, %) against concentration of the investigated component in aqueous or organic phase. In some of the systems of the systems studied practically quantitative extraction of pertechnetate into organic phase has been achieved.     

Adsorption of radioisotopes from their organic solutions on filter papers the Sb(III)-nonpolar solvents-system

The extraction of Sb(III) chloride by nonpolar solvents from 0.15M HCl was studied as a function of sulphuric acid concentrations in the aqueous phase. The distribution of Sb(III) chloride between the nonpolar solvents benzene, toluene, xylene, nitrobenzene, cyclohexane, chloroform and carbon tetrachloride and filter paper is reported. In case of benzene the Sb(III) activity (given in counts·s^–1·ml^–1) decreases from 1500 to 200 after 24 hours. The corresponding values are about 1200 and 540 for toluene, 1330 and 50 for xylene, 1050 and 700 for nitrobezene, 1080 and 22 for cyclohexane, 330 and 30 for chloroform and 130 and 40 for carbon tetrachloride. More than 95% of the adsorbed Sb(III) is desorbed by 1M HNO₃, 1M HCl or 0.5M H₂SO₄ by contacting the loaded filter paper with any of these acids for 27 hours.     

A study of radiation effects on the extraction of americium(III) with acidic organophosphates

Radiation effects on the extraction of americium(III) with several dialkylphosphoric and monoalkylphosphoric acids have been studied comparatively. The extractants were exposed to⁶⁰Co γ-rays in the absence and presence of diluent and HNO₃. The Df of Am(III) was measured and the yield of radiolytic products was determined after γ-irradiation as a function of the absorbed dose. Di(hexoxyethyl)phosphoric acid was the most susceptible to radiation among the extractants studied and its extractability was weakened by radiation regardless of the presence or absence of diluent or HNO₃. Diisodecylphosphoric acid itself showed an enhancement upon irradiation but incurred a depressant effect upon intimate contact with HNO₃·Mono(2-ethylhexyl)phosphoric acid showed a decrease of the Df of Am(III), similarly to DIDPA in the presence of HNO₃ during γ-irradiation. All the above extractants gave H₃PO₄ as the principal radiolytic product upon γ-irradiation upon intimate contact with HNO₃ causing decreasing solely the extraction of Am(III). Di(2-ethylhexyl)phosphoric acid proved to be the most stable extractant to radiation among those studied.     

Preparation of 99Mo/99mTc generator based on alumina 99Mo-molybdate (VI) gel

In this work alumina ⁹⁹Mo-molybdate (VI) gel is evaluated as a column matrix for use in the preparation of small chromatographic column type ^99mTc generator. Alumina molybdate (VI) gel is prepared by dissolving inactive MoO₃ with aluminum foil in 5 M NaOH solution containing ⁹⁹Mo radiotracer. After complete dissolution, 0.5 H₂O₂ was added to the reaction mixture solution and acidified to pH 5.5 with concentrated HNO₃. The formed AlMo precipitate was washed with NaNO₃ solution, dried at 50 °C for 24 h and then packed in the form of a chromatographic column for elution of the generated ^99mTc radionuclide with physiological saline solution (0.9 % NaCl). Greater than 86 % of the generated ^99mTc activity is immediately and reproducibly eluted with passing 10 mL of the saline solution through 2.0 g of alumina ⁹⁹Mo-molybdate column bed at a flow rate of about 1.0 mL/min. The high radiochemical ≥98.6 % TcO₄ ^?, radionuclidic ≥99.90 % ^99mTc and chemical purities of the eluates satisfy the specifications for use in nuclear medicine.     

Separation of tin from some metals by extraction chromatography

Much attention has been devoted to Sn (IV) strongly retained on the TBP-Daiflon column from 2M HCl in extraction chromatography. The separations of Sn?Cu, Zn, As, Cd, Sb, Pb,¹¹³Sn-¹²⁵Sb,¹¹³Sn-^113mIn (^113mIn milking) and Sn?Hg?Fe were successfully achieved without any contamination. In the separations, except for the last, only tin was retained separately on the column upon passing the mixed solution. The daughter indium was eluted with 0.5M HCl. In the last separation, iron was eluted with 0.5 M HCl, tin with 0.1M HCl and mercury with 2M HNO₃, for these metals retained on the column. Radioactive tracers for tin, iron, mercury and antimony were used.     

Liquid-liquid extraction of uranium(VI) from aqueous acidic solutions using Alamine, TBP and CYANEX systems

Liquid-liquid extraction of uranium(VI) (UO₂ ²⁺) from aqueous acidic (HCl and HNO₃) solutions into a co-existing organic phase containing Alamine 308 (triisooctyl amine), TBP (tri-n-butyl phosphate) or CYANEX 302 (bis(2,4,4-trimethylpentyl) monothiophosphinic acid) and diluent (toluene) was studied at isothermal conditions (298.2 K) at aqueous phase acidity varying in the range 0.5-6 mol/dm³. All solvent systems exhibit a maximum distribution ratio restricted in the acidity range 3-4 mol/dm³. An obvious difference in extraction behavior through amine system has been observed for two acids, HCl and HNO₃, distinguishing the divergent interactions attributed to the different mechanism of complexation depending on the acidic medium. The high degree of separation of UO₂ ²⁺ from HNO₃ solution is feasible through a complex formation with extractants ranging in the order CYANEX 302 > TBP > Alamine 308. The results were correlated using various versions of the mass action law, i.e., a chemodel approach and a modified version of the Langmuir equilibrium model comprising the formation of one or at least two U(VI)-extractant aggregated structures.