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.     

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.     

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.     

The extraction of uranium(VI), americium and europium by LIX 64 and by a mixture of LIX 64 and tri-n-octylphosphine oxide

The extraction of U(VI), Eu and Am by the aromatic main component (HA) of LIX 64N dissolved in toluene was studied at pH 3–9. The values of pH_1/2 for the extraction with 0.146 M HA are 4.0, 5.5 and 5.2, and the pH's of maximum extraction are 6.0, 6.8, and 7.0 for U(VI), Eu and Am, respectively. The stoichiometry of the extracted chelates determined by the slope analysis is UO₂A₂ and MA_3–nY_n (n=1,2) for Eu and Am, the ligand Y being probably the nitrate anion. The addition of tri-n-octylphosphine oxide (TOPO) enhances the extraction of U(VI) and especially of Eu at pH<6. An Eu chelate species solvated by 2 TOPO molecules is extracted at pH 4 by the mixture of HA+TOPO, whereas the species extracted at pH 6.5 is not solvated by TOPO.     

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.     

Solvent extraction and spectrophotometric determination of uranium (VI)

Summary Solvent extraction of uranium-sodium diethyldithiocarbamate with ethylmethyl ketone and separation from titanium, zirconium, thorium, lanthanum and cerium has been described. It has been found that 11.75 to 47.00 mg of uranium can be extracted from a binary mixture containing 4.78 to 19.04 mg of titanium, 9.12 to 36.48 mg of zirconium, 116.0 to 460.0 mg of thorium, 6.95 to 27.8 mg of lanthanum or 7.06 to 28.24 mg of cerium at pH 3.0. The pH range between which the separations may be carried out successfully is 2.0 to 3.5. The following cations interfere in the separations: Cu^II, Fe^III, Co^II, Bi^III, Ni^II, Cr^VI, Te^IV, Se^IV, Ag^I, Hg^II, As^III, Sn^IV, Pb^IV, Cd^II, Mo^VI, Mn^II, V^V, Zn^II, In^III, Tl^I, W^VI, Os^VIII and Nb^V.

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Zusammenfassung Uran kann durch Extraktion als Diäthyldithiocarbamidat mit Methyläthylketon von Ti, Zr, Th, La oder Ce getrennt werden. Der günstigste pH-Bereich liegt zwischen 2,0 und 3,5. Die Trennungen wurden mit folgenden Mengen durchgeführt: U (11,75–47,00 mg); Ti (4,78 bis 19,04 mg), Zr (9,12–36,48 mg) Th (116,0–460,0 mg), La (6,95–27,8 mg), Ce (7,06–28,24 mg). Folgende Ionen verursachen Störungen: Cu^II, Fe^III, Co^II, Bi^III, Ni^II, Cr^VI, Te^IV, Se^IV, Ag^I, Hg^II, As^III, Sn^IV, Pb^IV, Cd^II, Mo^VI, Mn^II, V^VI, Zn^II, In^III, Tl^I, W^VI, Os^VIII sowie Nb^V.

     

Synergistic extraction and separation studies of uranium(VI)

A method is described for the extractive separation and spectrophotometric determination of uranium(VI) from an aqueous solution of pH 5.0–7.0 using benzoylacetone (bzac) and pyridine (py) dissolved in toluene as extractants. The extracted species are UO₂(bzac(₂·2py. The method provides separation of uranium(VI) from lanthanum(III), samarium(III), neodymium(III), cerium(III) and thorium(IV). The method is precise, accurate, fast and selective.     

The extraction equilibrium of uranium(VI) with i-butyldodecylsulfoxide (BDSO)

The i-butyldodecylsulfoxide (BDSO) was synthesized. The extraction of uranium(VI) has been carried out with BDSO in toluene from various HNO₃ concentrations. It was found that the distribution ratio increases with increasing nitric acid concentration up to 3.0 mol/l and then decreases. The distribution ratios also increase with increasing extractant concentration. The extracted species appears to be UO₂(NO₃)₂·2BDSO and the equilibrium constant value is 15.2. The influence of temperature, sodium nitrate and oxalate concentrations on the extraction was also investigated, and the thermodynamic functions of the extraction reaction were obtained.This revised version was published online in November 2005 with corrections to the Cover Date.     

Liquid-liquid extraction of uranium(VI) with 2-ethylhexyltolylsulfoxide (EHTSO)

The liquid-liquid extraction behavior of 2-ethylhexyltolylsulfoxide (EHTSO) towards uranium(VI) contained in nitric acid aqueous solution has been investigated. It was found that the extraction increases with increasing nitric acid concentration up to 5.0 mol/l and then decreases. Extraction also increases with increasing extractant concentration. The extracted species appears to be UO₂(NO₃)₂ ^.2EHTSO. The influences of temperature, NH₄NO₃ and Na₂C₂O₄ concentrations on the extraction equilibrium were also investigated and the thermodynamic functions of the extraction reaction were obtained.     

Kinetics of uranium(VI) extraction by bis(octylsulfinyl)methane

The kinetics and mechanism of uranium(VI) extraction from nitric acid solution by bis(octylsulfinyl)methane (BOSM) are studied with the method of stationary interface cell. The effects of temperature, extractant and nitric acid concentrations are discussed. The results showed that the extraction process is controlled by the following reaction: UO₂(NO₃)₂ + BOSM_(i)⇄_k1 ^k-1UO₂(NO₃)₂BOSM_(i). The variation of enthalpy associated with the extraction is -22.1±2.1 kJ/mol. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

螯合-酸性磷萃取剂对铀(VI)的协同萃取

本文研究了螯合-酸性磷协同萃取体系─1-苯基-3-甲基-4-(2'-氯苯甲酰基)-5-吡唑啉酮(PMCBP)与磷酸二(2-乙基己基)酯(HDEHP)和2-乙基己基膦酸-单-2-乙基己基酯(HEHEHP)的氯仿溶液从硫酸介质中对铀(VI)的萃取。实验发现均有明显的协同效应存在。采用斜率法测定了协萃配合物的组成为UO2HA2X和UO2HA2HXX'的混合物, 计算了它们的萃取平衡常数, 讨论了协萃机理。     

Concurrent adsorption and complex formation in reversed-phase liquid-liquid chromatography with tri-n-octylphosphine oxide

Summary Reversed-phase liquid-liquid chromatographic systems consisting of an aqueous mobile phase and an organic liquid stationary phase of the proton acceptor tri-n-octylphosphine oxide (TOPO) inn-decane, coated on LiChrosorb RP-8, have been studied. The solutes were hydrophilic aromatic carboxylic acids and phenol. The retention of the carboxylic acids shows a minimum at 10 mM of TOPO, whereas increasingly tailing peaks have been obtained with decreasing concentrations of TOPO. This behaviour is due to a concurrent complex formation by hydrogen bonding with TOPO in the liquid stationary phase and adsorption at the interface between the support and the liquid stationary phase. The adsorption of TOPO, ketones and aromatic acids from hexane on Li-Chrosorb RP-8 has been studied, and seems to be due to residual silanol groups. The adsorption isotherm of TOPO has been determined and can be described by a two-site Langmuir adsorption model. Non polar solutes are not adsorbed. The influence of TOPO on the retention and the peak symmetry of carboxylic acids in the liquid-liquid chromatographic system appears to be due to a competition between TOPO and the acids for the same adsorption sites. No competition was found for phenol.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Synergistic extraction of uranium(VI) with tri-n-butyl phosphate and i-butyldodecylsulfoxide

Summary The synergistic extraction of uranium(VI) from aqueous nitric acid solution with a mixture of tri-n-butyl phosphate (TBP) and i-butyldodecylsulfoxide (BDSO) in toluene was investigated. The effects of the concentrations of extractant, nitric acid, sodium nitrate and sodium oxalate on the distribution ratios of uranium(VI) have been studied. The values of enthalpy change for the extraction reactions with BDSO, TBP and a mixture of TBP and BDSO in toluene were -23.2±0.8 kJ/mol, -29.2±1.4 kJ/mol and -30.6±0.6 kJ/mol, respectively. It has been found that the maximum synergistic extraction effect occurs when the molar ratio of TBP to BDSO is close to 1. The composition of the complex of the synergistic extraction is UO₂(NO₃)₂ ^. BDSO ^. TBP.     

Uranium(VI) extraction by Winsor II microemulsion systems using trialkyl phosphine oxide

Summary The parameters affecting the formation of the microemulsion were investigated and the microemulsion region was determined. The extraction of uranium(VI) from HNO₃ solution into a water in oil microemulsion was studied. The effects of the concentration of extractant (TRPO), the volume ratio of oil to water and the acidity of outer water phase on the extraction equilibrium of uranium(VI) are discussed and the appropriate conditions are obtained. The result showed the microemulsion has great efficiency for uranium(VI) extraction.