Extraction of certain actinide and lanthanide elements from different acid media by polyurethane foams loaded with di(2-ethylhexyl)phosphoric acid (HDEHP)

The extraction of uranium(VI) from an aqueous HNO₃ phase into an organic phase consisting of a polyurethane foam immobilizing a solution of di(2-ethylhexyl)phosphoric acid (HDEHP) in o-dichlorobenzene has been investigated at varying concentrations of nitric acid and HDEHP. The mechanism of the extraction is discussed on the basis of the results obtained. The aggregation number of HDEHP immobilized on the foam was obtained from the analysis of data obtained for the extraction of cerium(III) from acidic perchlorate solutions of constant ionic strength.     

Role of Cyanex-272 as an extractant for uranium in the determination of rare earths by ICP-AES

A chemical separation procedure has been developed for the extraction of uranium from some of the crucially important rare earths using a novel extractant viz. Cyanex-272 (2,4,4-trimethyl pentyl phosphinic acid). The near total extraction of uranium and quantitative separation of rare earth elements has been validated using inductively coupled argon plasma - atomic emission spectrometry (ICP-AES). The recovery of some of the representative elements has been confirmed by radioactive tracer studies. The back extraction of uranium from the organic phase was carried out using a solution of 0.5M Na₂CO₃ which resulted in a near total recovery of uranium into the organic phase. These studies have enabled determination of sub ppm amounts of the analyte elements with a precision of 5% RSD utilizing prior chemical separation of rare earths from 1 g uranium samples in just three extractions with Cyanex-272.     

Extraction Kinetics of Uranium(VI) with di(2-ethylhexyl) Phosphoric Acid Using a Hollow Fiber Membrane Extractor

The kinetics of solvent extraction of U(VI) with di(2-ethylhexyl) phosphoric acid (HDEHP) using a microporous hydrophobic hollow fiber membrane extractor has been investigated. The effects of U(VI) and hydrogen ion concentrations in aqueous phase, HDEHP concentration in organic phase, flow velocities of aqueous and organic phase and temperature on extraction rate of U(VI) were examined. The experimental results suggest that the extraction rate of U(VI) is controlled by diffusion.     

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.     

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.     

Determination of major,minor and trace elements in Iraqi vegetable samples by INAA

Our aim was to discover a method of separating zirconium(IV) and uranium(VI) from solutions. It is known that Zr(IV) and U(VI) are effectively extracted by tertiary amines from weak acidic sulfate solutions but the possibility of extraction decreases with increasing acidity. The transition from tertiary amine to primary amine Primene JMT enables the extraction of Zr also from more acidic solution. If both Zr and U are present in an aqueous solution, Zr is extracted preferentially and only the free part of the amine can convert uranium to an extract. The separation described below was carried out by preferentially stripping zirconium from the organic phase. The application of nitrate solution (2M HNO₃) to eliminate Zr from the solvent was tested. This method does not demand any special regeneration of the extraction agent and the amine nitrate, formed in the organic phase, can be used for further extraction of Zr without modification. Using this method of separation, a solution for producing pure ZrOCl₂·8H₂O was obtained.     

Characterization of hot particles in surface soil around the Chernobyl NPP

An ICP-AES method for the analysis of trace amounts of lanthanides and yttrium in sodium or magnesium diuranate samples (yellow cake) and other beneficiation product generated during the uranium extraction process (hydrometallurgy) from its ores is described. Most of the matrix elements are removed by an initial oxalate precipitation of lanthanides using calcium as carrier. A solvent extraction procedure using a mixture of mono 2-ethylhexyl dihydrogen phosphate (H₂MEHP) and bis (2-ethylhexyl) hydrogen phosphate (HDEHP) is used for the removal of calcium, iron and the occluded uranium. A combination of oxalate precipitation and solvent extraction procedure is applied for the selective separation and preconcentration of traces of lanthanides from yellow cake and iron cake samples. The solvent extraction procedure is directly applied for the separation of lanthanides from the uranium leach liquor and lime cake. The accuracy of the method is checked by analyzing synthetic mixture containing known amounts of traces of lanthanides and also by comparing with another standard separation procedure like ion exchange method, and the recovery was better than 95%. The method is rapid, simple, accurate and suitable for the separation of lanthanides from uranium, iron and calcium rich materials. The precision of the method is characterized by an RSD of 2 to 4%.     

Extraction of rare earth elements with organophosphorus extractants as carriers in supported liquid membranes

The membrane extraction of Y, Ce, Eu, Tm and their binary mixtures Ce–Y, Ce–Eu, Ce–Tm with supported liquid membranes containing TBP and HDEHP as carriers in decanedodecane hydrocarbon solvent, has been studied. Upon extraction with TBP aqueous nitrate solutions of rare earth elements (REE) were used as feed phase. In some cases they also contained EDTA or DCTA. In most cases, the receiving phase was an aqueous solution of EDTA. Extraction with HDEHP was performed from nitrate and chloride solutions and the receiving phase was the corresponding dilute acid. Pertraction of an element through a membrane was studied as a function of time and of initial composition of phases. The results are presented in the following forms: flux of metal through membrane, coefficients of permeability, separation factors and effective diffusion coefficients.     

An effective process for the separation of U(VI), Th(IV) from rare earth elements by using ionic liquid Cyphos IL 104

Separation and recovery of U(VI) and Th(IV) from rare earth minerals is a very challenging work in rare earth industrial production. In the present study, a homemade membrane emulsification circulation (MEC) extractor was used to separate U(VI) and Th(IV) from rare earth elements by using Cyphos IL 104 as an extractant. Batch experiments were carried out using a constant temperature oscillator to investigate the extraction parameters of the single element and the results indicated that Cyphos IL 104 could reach the extraction equilibrium within 30 min for all the three elements, i.e., U(VI), Th(IV), and Eu(III). Besides, the MEC extractor possessed a strong phase separation ability. The extraction efficiencies of U(VI), Th(IV), La(III), Eu(III) and Yb (III) increased with the increase of pH. La(III), Eu(III) and Yb(III) were hardly extracted when pH ≤ 1.50, which was beneficial for effectively separating U(VI) and Th(IV) from La(III), Eu(III) and Yb(III). In the multi-stages stripping experiments, when the stripping stage number was 3, the effective separation could be achieved by using HCl and H₂SO₄, since the stripping efficiency reached 80.0% and 100.0% for Th(IV) and U(VI), respectively. Slope method and FT-IR spectra showed that Cyphos IL 104 reacted with U(VI) and Th(IV) by chelation mechanism. The extraction of multi-elements indicated that U(VI) and Th(IV) could be well separated from the solution which contains all rare earth elements, and the extraction efficiencies of U(VI) and Th(IV) both were close to 100.0%. Based on the above experimental results, a flowchart for efficient separation of U(VI) and Th(IV) from rare earth elements was proposed.     

Extractive separation of Th(IV), U(VI), Ti(IV), La(III) and Fe(III) from Zarigan ore

In this study, the effects of various extraction parameters such as extractant types (Cyanex302, Cyanex272, TBP), acid type (nitric, sulfuric, hydrochloric) and their concentrations were studied on the thorium separation efficiency from uranium(VI), titanium(IV), lanthanum(III), iron(III) using Taguchi^??s method. Results showed that, all these variables had significant effects on the selective thorium separation. The optimum separations of thorium from uranium, titanium and iron were achieved by Cyanex302. The aqueous solutions of 0.01 and 1 M nitric acid were found as the best aqueous conditions for separating of thorium from titanium (or iron) and uranium, respectively. The combination of 0.01 M nitric acid and Cyanex272 were found that to be the optimum conditions for the selective separation of thorium from lanthanum. The results also showed that TBP could selectively extract all studied elements into organic phase leaving thorium behind in the aqueous phase. Detailed experiments showed that 0.5 M HNO₃ is the optimum acid concentration for separating of thorium from other elements with acidic extractants such as Cyanex272 and Cyanex302. The two-stage process containing TBP-Cyanex302 was proposed for separation thorium and uranium from Zarigan ore leachate.     

Separation of Uranium(VI) by Extraction with Dibutylditiophosphoric Acid

The extraction of uranium(VI) from aqueous solutions with dibutylditiophosphoric acid in organic solvents was studied. The influence of different factors as pH of the aqueous phase, extractant concentration and nature of solvent was investigated in order to find the optimum conditions for separation of metal from aqueous nitrate solutions. The effect of neutral donor extractants was also searched and the efficiency of the extraction was calculated.     

Liquid-liquid extraction of uranium(VI) from nitric acid solutions with bis(octylsulfinyl)ethane (BOSE)

The liquid-liquid extraction behavior of uranium(VI) from aqueous nitric acid with bis(octylsulfinyl)ethane (BOSE) in 1,1,2,2-tetrachloroethane has been studied over a wide range of conditions. The extracted species appears to be UO₂(NO₃)₂·2BOSE. It was found that the extraction increases with increasing nitric acid concentration up to 7 mol/l and then decreased. Extraction also increases with increasing extractant concentration. The influence of temperature and salting-out agent concentration on the extraction equilibrium and stripping of uranium(VI) was also investigated and the enthalpy of the extraction reaction was obtained.     

Extraction of plutonium from sulphuric acid by TOA in toluene

The extraction of plutonium(VI) and plutonium(III) from sulphuric acid by TOA in toluene has been studied as a function of the acid and tri-octyl amine concentration. A comparison of the extraction properties of plutonium with those of uranium(VI) and uranium(IV) has been made. It was found that the extraction properties of plutonium(VI) are very similar to those of uranium(VI) and that TOA is a relatively poor extractant for plutonium(III). Uranium(IV) shows better extraction properties than plutonium(III). The results obtained are considered in the light of the stabilities of the complexes formed by these elements in the organic and aqueous phase. A method of separation of both elements by solvent extraction based on changing their oxidation states is suggested.     

Kinetic studies on the solvent extraction of uranium(VI) from phosphoric acid solution with HDEHP using laser-induced optical fiber fluorimetry

Laser-induced optical fiber fluorimetry has been first used to analyze uranium(VI) concentration in the kinetic studies on the extraction of uranium(VI) between 0.5 mol/l H₃PO₄ solution and HDEHP-cyclohexane system with a Lewis cell. The effects of stirring speed, temperature and concentrations of uranium(VI) and HDEHP on the rate of extraction were examined. These data show that the extraction rate of uranium(VI) in this system is controlled by the chemical reaction at the interface. The rate equations and the rate constants of forward and reverse extraction are obtained. The mechanism of the extraction is discussed.     

The application of extraction chromatography for analysis of alkali and alkaline earth uranates

A method for rapid analysis of alkali and alkaline earth uranates is proposed. The method is based on the use of an HDEHP extraction chromatographic column, which makes possible quantitative separations of alkali or alkaline earth ions from macroamounts of uranium (VI).     

Kinetic studies on the solvent extraction of uranium(VI) from phosphoric acid solution with HDEHP using laser-induced optical fiber fluorimetry

The laser-induced optical fiber fluorimetry has been used for the first time to analyse the concentration of uranium(VI) in the kinetic studies on the extraction of uranium(VI) between 0.5 mol L H₃PO₄ solution and HDEHP-cyclohexane system with Lewis cell. The effects of stirring speed, temperature and concentration of uranium(VI) and HDEHP on the rate of extraction were examined. These data show that the extraction rate of uranium(VI) in this system is controlled by the chemical reaction process at the interface. The rate equations and the rate constants of the forward and reverse extractions were obtained. The mechanism of the extraction has been discussed.     

Solvent extraction of uranium(VI) and separation of vanadium(V) from sulfate solutions using Alamine 336

The present scientific study on uranium(VI) solvent extraction and vanadium(V) separation from sulfate solutions using Alamine 336 as an extractant diluted in kerosene was established. The preliminary experiments indicating the uranium extraction process will follow the solvation as well as ion-exchange mechanisms. In the present acid region (0.1–1.0 mol dm⁻³ H₂SO₄) it showing the ion-exchange type mechanism. Time (1–120 min) and temperature (25–55 °C) not influencing the present extraction system. Other experimental parameters like loading capacity of Alamine 336, stripping of uranium from loaded organic phase, recycling of Alamine 336 and separation of uranium(VI)/vanadium(V) was studied.     

Separation and Extraction of Uranium from Leach Liquor Containing Uranium and Molybdenum by Solvent Extraction with LIX 622N

The leach liquor (0.5 g/L Mo, 0.05 g/L U) obtained from the leaching process of molybdenum-uranium ore material was treated using solvent extraction to recover U(VI) by LIX 622N, which is a salicylaldoxime derivative. The influence of various basic variables such as pH, concentration of LIX 622N, temperature, different stripping reagents, phase ratio, and diluents was examined. Using 10% LIX 622N with the aqueous solution of equilibrium pH 6.0 and a phase ratio organic phase:aqueous phase (O:A) = 1:1, a two-stage McCabe-Thiele plot was constructed, which showed 99.9% of U extraction with no co-extraction of molybdenum. This was confirmed by a 6-cycle counter current simulation (CCS) study. The obtained data of temperature on the extraction of uranium showed that the extraction process is exothermic with enthalpy change of ?20.949 kJ mol^?1. The stripping of U(VI) was quantitative using 4 M H₂SO₄. The stable complex UO₂(HSO₄)R_org formed during extraction, which supports the cation exchange mechanism, and was confirmed by FTIR spectral analysis.      

Complexation of uranium(VI) with acetohydroxamic acid

The advanced separation extraction process based on tri-n-butyl phosphate organic phase called UREX is being developed to separate uranium from fission products and other actinides, and the acetohydroxamic acid (AHA) is employed to reduce and complex plutonium and neptunium in order to decrease their distribution to the TBP-organic phase. In this study, the extraction of uranium was performed from various aqueous matrices with different concentrations of HNO₃, LiNO₃, and AHA. Extraction of uranium increases with increasing both initial HNO₃ and total nitrate concentration. UV-VIS spectrophotometry confirmed that AHA is involved in the complex of uranium with TBP.     

Extraction of uranium(VI) and thorium(IV) from nitric acid solution by N-alkylcaprolactam

Extraction of uranium(VI), thorium(IV) from nitric acid has been studied with N-octylcaprolactam and N-(2-ethyl)hexylcaprolactam. Distribution coefficients of U(VI), Th(IV) and HNO₃ as a function of aqueous NHO₃ concentration, extractant concentration and temperature have been studied. The compositions of extracted species, thermodynamic parameters of extraction have been evaluated. Third phase formation in extraction of U(VI) has been studied. Back extraction behavior of U(VI) and Th(IV) from the organic phase has also been tested. The results obtained are compared with those obtained by using TBP under the same experimental conditions.