Homogeneous liquid-liquid extraction of uranium(VI) using tri-n-octylphosphine oxide.

A simple and efficient method for the selective separation and preconcentration of uranium(VI) using homogeneous liquid-liquid extraction was developed. Tri-n-octylphosphine oxide (TOPO) and tri-n-butylphosphate (TBP) were investigated as complexing ligands, and perfluorooctanoate ion (PFOA-) was applied as a phase separator agent under strongly acidic conditions. Under the optimal conditions ([PFOA-] = 1.7 x 10(-3) M, [TOPO] = 5.4 x 10(-4) M, [HNO3] = 0.3 M, [acetone] = 3.2% v/v) 10 microg of uranium in 40 ml aqueous phase could be extracted quantitatively into 8 microl of the sedimented phase. The maximum concentration factor was 5000-fold. However, an effort for the quantitative extraction using TBP was inefficient and the percent recovery was at most 56.7. The influence of the type and concentration of acid solution, optimum amount of the ligand, type and volume of the organic solvent, concentration of PFOA, volume of the aqueous sample and effect of different diverse ions on the extraction and determination of uranium(VI) were investigated. The proposed method was applied to the extraction and determination of uranium(VI) in natural water samples.     

Separation and spectrophotometric determination of uranium(VI) by extraction with tri-n-octylphosphine oxide and benzophenone

Uranium(VI) is separated by extraction from nitric acid medium into a molten mixture of tri-n-octylphosphine oxide and benzophenone at about 50°. The organic phase solidifies on cooling and is separated and dissolved in ethanol. The uranium(VI) in this solution is then determined spectrophotometrically with 1-(2-pyridylazo)-2-naphthol.     

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 uranium(vi) by liquid-solid extraction with tri-n-octylphosphine oxide diluted with naphthalene

Liquid-liquid distribution with tri-n-octylphosphine oxide (TOPO)and molten naphthalene has been investigated for the extraction of 20 metals from nitric acid and hydrochloric acid solutions. Uranium is quantitatively extracted from 1 M nitric acid or hydrochloric acid by using 100 mg of TOPO and 200 mg of naphthalene and shaking for 5 min at 80°C, and separated from transition metals, alkaline earth metals and rare earth metals (except scandium). Addition of naphthalene increases the extraction efficiency.     

Extraction of europium and americium by a mixture of CMPO and dicarbollide

The extraction of Eu³⁺ and Am³⁺ by a mixture of CMPO and dicarbollide in nitrobenzene has been studied. The synergetic effect of dicarbollide is pronounced at low acidities but still lower than for previously studied DBDECMP. Separation properties towards Am/Eu pair are small.     

Selective extraction of plutonium(IV) over uranium(VI), americium(III), europium(III) and zirconium(IV) with bidentate O-phenoxydiamide ligands: experimental and theoretical study

To rapidly assess the contamination of actinides in emergency water, a method was developed to simultaneously analyze U, Th, Pu and Am. The method consists of two steps: extraction chromatographic separation using UTEVA and DGA resins and isotopic determination of actinides by inductively coupled plasma mass spectrometry (ICPMS). The whole analytical procedure takes only 8 h and high chemical recoveries of actinides were obtained. The cross spectral interferences between actinides in ICPMS measurement were sufficiently removed. The accuracy was validated by analyzing IAEA-443 seawater sample. The low limits of detection of actinides allow this method to distinguish low level contamination.     

LIX 84 as an extractant for throium(IV), uranium(VI) and molybdenum(VI)

The extraction order of Th(IV), U(VI) and Mo(VI) based on pH_0.5 values is Mo(VI)>U(VI)>Th(IV). Quantitative extraction has been observed for U(VI) by mixture of 10% (v/v) LIX 84 and 0.1M dibenzoylmethane at pH 4.2 and by mixture of 10% LIX 84 and 0.05M HTTA in the pH range 5.5–7.3 and for Mo(VI) by 10% LIX 84 from chloride media at pH 1.5. The order of extraction of Mo(VI) from 1N acid solutions is HCl>H₂SO₄>HNO₃>HClO₄ and extraction decreases very rapidly with increase in the concentration of HCl as compared to that from H₂SO₄, HNO₃ and HClO₄ acid solutions. The diluents C₆H₆, CCl₄ and CHCl₂ are found to be superior ton-butyl alcohol and isoamyl alcohol for extraction of Mo(VI). Influence of concentration of different anions on the extraction of U(VI) and Mo(VI) has been studied. Very little extraction has been observed in case of Th(IV) by LIX 84 or its mixtures with other chelating extractants or neutral donors.     

Spectrophotometric determination of uranium(VI) by solvent extraction with trioctylphosphine oxide and a molten mixture of biphenyl and naphthalene

Uranium in ores has been determined spectrophotometrically after extraction with trioctylphosphine oxide (TOPO) into a molten mixture of biphenyl and naphthalene. By addition of salting-out agents such as sodium nitrate to the aqueous phase and cooling, the organic phase can be obtained as a solid lump on the surface of the aqueous phase, making its collection simple. The uranium can then be determined directly in the organic phase with 1-(2-pyridylazo)-2-naphthol or 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol.     

A Study on the extraction of uranium(VI) from sulphate leach liquor using LIX63

The sulphate leach liquor obtained from the sulphuric acid leaching process of Egyptian monazite was treated using solvent extraction to recover U(VI) by LIX63. The influence of various basic variables such as pH, concentration of LIX63, temperature, different stripping agent, phase ratio and diluents was examined. Using 10% LIX63 with the aqueous solution at equilibrium pH 5.5 and a phase ratio A/O?=?1/1, a four-stage McCabe-Thiele plot was constructed, which showed 85.57% of U(VI) extraction. The thermodynamic data showed that the extraction process is exothermic with enthalpy change ΔH?=???43.866?kJ/mol, the stripping of U(VI) was quantitative using 4?M HNO₃. The stable complex UO₂(HSO₄)R_org formed during extraction which supports the cation exchange mechanism was confirmed by FTIR spectral analysis. Uranium cake was finally obtained from the strip solution by the addition of hydrogen peroxide and ammonium hydroxide as precipitating agents, and a workable flowsheet was then formulated.     

Effect of gamma-radiation on the extraction of europium and americium by benzyldibutylamine

The effect of gamma irradiation on benzene solutions of benzyldibutylamine with cetyl alcohol used for the extraction of europium and americium from nitrate solutions was investigated. The dependence of the distribution coefficient on the dose absorbed either by the whole system or some efficient component was measured. Nitric acid present during irradiation significantly lowers the radiation stability, while benzyldibutylamine and cetyl alcohol appear to be radiostable components. Up to tens of kGy's—the doses expected in an extraction process from highly active solutions—the system seems to be quite stable.     

Synergic extraction of uranium from phosphate solutions with di-(2 ethylhexyl) phosphotic acid and tri-n-octylphosphine oxide

The synergic extraction of uranium from concentrated aqueous phosphate solutions with di-(2 ethylhexyl) phosphoric acid and tri-n-octylphosphine oxide in kerosene has led to an investigation of the complex species formed by the U(VI) in the organic phase. The role of the phosphoric acid concentration in forming complex species in the aqueous phase which interfere seriously with the extraction process has been explored. It was found that U(VI) was extracted in the organic phase as UO₂X₂(HX)₂mTOPO where m ⩽ 1 depending on the TOPO concentration. Increasing temperature also diminishes the extraction coefficient. An investigation of the latter effect led to values of the enthalpy changes for the process. Ferrous iron reduces U(VI) in acid phosphate media and in the case of U(IV) there is no synergic effect, in agreement with the fact that the U(IV) complexes are coordinatively saturated.Moreover this synergic system gives fairly good extraction coefficients even in concentrated solutions of phosphoric acid.     

Solvent extraction behaviour of lanthanum(III), cerium(III), europium(III), thorium(IV) and uranium(VI) with 3-phenyl-4-benzoyl-5-isoxazolone

The extraction behaviour of La(III), Ce(III), Eu(III), Th(IV) and U(VI) with 3-phenyl-4- benzoyl-5-isoxazolone (HPBI) in chloroform has been studied. The mechanism of extraction and the species extracted have been identified. Extraction constants for each system have been calculated. The system has been used to separate Th(IV) from U(VI) and from La(III), Ce(III) and Eu(III). A comparison of the extraction constants with those for the 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HPMBP) and thenoyltrifluoroacetone (HTTA) systems indicates that HPBI extracts these metal species better than HPMBP and HTTA do.     

Effect of gamma-radiation on the extraction of europium and americium by benzyldimethyldodecylammonium nitrate

Previously it was found that in the extraction separation on lanthanides and americium from acidic nitrate solutions of nuclear fission products, benzyldimethyldodecylammonium nitrate gives high values of separation coefficients. The change in the extraction capacity of this agent and its solutions in benzene in the extraction of Eu(III) and Am(III) was investigated as a function of the adsorbed dose of ionizing radiation. The slight reduction in the extraction of both metals is caused mainly by the radiolysis products of nitric acid in the organic phase that enter into secondary reactions with both the solvent and the extractant. Comparison of the radiation stability of benzyldimethyldodecylammonium nitrate systems with tertiary amines show that the changes in distribution coefficients in the range of investigated absorbed doses are significantly lower in the former case. The investigated system may be characterized as radiation stable up to about 100 kGy even in the presence of nitric acid.     

Solvent extraction of microamounts of europium and americium into nitrobenzene by using synergistic mixture of hydrogen dicarbollylcobaltate and 1,2-(diphenylphosphino)ethylene dioxide

Extraction of microamounts of strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of dibenzo-24-crown-8 (DB24C8, L) has been investigated. The equilibrium data have been explained assuming that the species HL⁺, HL₂ ⁺, ML²⁺, ML₂ ²⁺ and MHL₂ ³⁺ (M²⁺ = Sr²⁺, Ba²⁺) are extracted into the organic phase. The values of extraction and stability constants of the complexes in nitrobenzene saturated with water have been determined. It was found that the stability constants of the cationic complex species BaL²⁺ and BaL₂ ²⁺ in the considered nitrobenzene medium are somewhat higher than those of the corresponding complexes SrL²⁺ and SrL₂ ²⁺.     

Flow fluorimetry of trace amounts of uranium(VI) after preconcentration on a tri-n-octylphosphine oxide/polyethylene column and elution with hydrogenphosphate solution

The fluorescence of uranyl ion is enhanced in phosphoric acid medium and in hydrogen-phosphate medium. The pH dependence of the fluorescence intensity showed maxima at pH 1–2 and pH 7–8. The concentration of phosphoric acid which gave maximum intensity was around 1 M, but in the hydrogenphosphate media an increase in the concentration lowered the intensity. The procedure was used in combination with preconcentration on a tri-n-octylphosphine oxide/polyethylene column. This simple system provided a limit of detection of 0.04 μg for uranium and the calibration graph was linear for the range 0.08–0.8 μg of uranium when 4–15 ml of sample solution was passed through the column. The flow fluorimetric method was applied to the determination of uranium in a spinel.     

Synergistic extraction of uranium(VI) from nitric acid solution by mixture of DMHMP and DOSO in benzene

Solvent extraction of uranyl nitrate in nitric acid medium with the binary system of DMHMP and DOSO has been investigated. It was found that synergistic effect occurs during the extraction of uranyl nitrate with benzene solution of DMHMP and DOSO, the binary species extracted UO₂ (NO₃)₂·DMHMP·DOSO has been confirmed. From the data the equilibrium constants have been determined.     

Antagonism in the extraction of uranium(VI) by the binary mixture of PC88A and benzimidazole

Extraction studies of uranium(VI) by the binary mixture of PC88A and benzimidazole show an antagonistic behavior in the concentration range 10⁻⁵–10⁻⁶M of PC88A and 0.005M of benzimidazole. Antagonism is observed due to the deprotonation of PC88A by benzimidazole forming an adduct resulting in the virtual removal of PC88A from the system.     

Complexation of lanthanides(III), americium(III), and uranium(VI) with bitopic N,O ligands: an experimental and theoretical study

New functionalized terpyridine-diamide ligands were recently developed for the group actinide separation by solvent extraction. In order to acquire a better understanding of their coordination mode in solution, protonation and complexation of lanthanides(III), americium(III), and uranium(VI) with these bitopic N,O-bearing ligands were studied in homogeneous methanol/water conditions by experimental and theoretical approaches. UV-visible spectrophotometry was used to determine the protonation and stability constants of te-tpyda and dedp-tpyda. The conformations of free and protonated forms of te-tpyda were investigated using NMR and theoretical calculations. The introduction of amide functional groups on the terpyridine moiety improved the extracting properties of these new ligands by lowering their basicity and enhancing the stability of the corresponding 1:1 complexes with lanthanides(III). Coordination of these ligands was studied by density functional theory and molecular dynamics calculations, especially to evaluate potential participation of hard oxygen and soft nitrogen atoms in actinide coordination and to correlate with their affinity and selectivity. Two predominant inner-sphere coordination modes were found from the calculations: one mode where the cation is coordinated by the nitrogen atoms of the cavity and by the amide oxygen atoms and the other mode where the cation is only coordinated by the two amide oxygen atoms and by solvent molecules. Further simulations and analysis of UV-visible spectra using both coordination modes indicate that inner-sphere coordination with direct complexation of the three nitrogen and two oxygen atoms to the cation leads to the most likely species in a methanol/water solution.     

Monitoring of urine by extraction chromatography with tri-n-octylphosphine oxide supported on a polypropylene column

Monitoring of personnel working with enriched uranium implies development of techniques for excreta analysis, mainly for urine, with very low detection limits.The method described allows the determination of enriched uranium after extraction in tri-n-octylphosphine oxide (TOPO), 0.5M in toluene, supported on polypropylene capillary columns¹. Alpha activity is later measured in a low background liquid scintillation equipment² and a fluorimetric determination is performed³ with detection limits for 800 ml of urine of 12±4 mBq/l and 0.08±0.01 ug/l.