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.     

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

The effect of added TBP on the extraction of uranium(VI) with a solution of di-(2-ethylhexyl)-phosphoric acid (HDEHP) in o-dichlorobenzene from nitric acid solutions has been investigated at varying concentrations of nitric acid, HDEHP, TBP and uranium(VI). The mechanism of the synergistic effect of TBP is discussed on the basis of the results and can be summarized in the following equation: UO _2(aq) ²⁺ +0.67(HX)_3(o)+2TBP_(o)UO₂X₂·2TBP_(o)+2H _(aq) ⁺ where HX denotes HDEHP and the HDEHP loaded on the foam is trimerized.     

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

The extraction of cerium(III) from weakly acidic chloride solutions by HDEHP-nitrobenzene-loaded polyurethane foams could be analyzed quantitatively in terms of the equation: log(9.056 D_c)=log K_c+2.14 log (C_d?6C_c)+3 pH+log f_c where D_c is the distribution ratio of cerium(III) between the foam and aqueous phases, C_d and C_c are the total HDEHP and Ce(III) concentrations on the foam, respectively, log f_c=[Ce³⁺]_(sq)/[ΣCe(III)]_(aq), and K_c is the equilibrium constant of the equation: Ce _(aq) ³⁺ +2.14(HX)_2.8(o) ? ? CeX₆·H_3(o)+3H _(aq) ⁺ . Values of K_c under the different extraction conditions tested are given.     

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

The partition of cerium(III) between aqueous acid perchlorate solutions and polyurethane foams loaded with solutions of di-(2-ethylhexyl)phosphoric acid (HDEHP) in nitrobenzene has been investigated and the apparent polymerization number of HDEHP on the foam has been determined. The mechanism of extraction is discussed in the light of the results. It has been found that Ce(III) is generally extracted on the foam by a cation exchange mechanism.     

Metal nanoparticle formation in oil media using di(2-ethylhexyl) phosphoric acid (HDEHP)

The metal ion extractant (HDEHP) that is commonly employed in liquid membrane extraction has been shown to stabilise Ag and Cu nanoparticles in oil media of size 5 and 10 nm, respectively. The particle are formed by reduction of the metal salts of HDEHP that are oil soluble and shown by SANS to form small reversed micelles of radius approximately 1 nm. The extractant is also effective at stabilising particles of similar size in an oil phase when the metal ion (e.g., AgNO3) is reduced in a coexisting aqueous phase.     

Extraction mechanism of Tc(IV) by Di-(2-ethylhexyl)phosphoric acid (HDEHP)

Journal of Radioanalytical and Nuclear Chemistry - Di-(2-ethylhexyl)phosphoric acid, HDEHP, is a well-known extractant used for metal ion extraction in an industrial scale and for research work....     

Extraction of actinium with di (2-ethylhexyl) phosphoric acid from hydrochloric and nitric acid solutions

The extraction of actinium with HDEHP from Cl^– and NO ₃ ^– systems has been investigated. It was found that extraction of actinium from HCl solutions is much better than from HNO₃ solutions. Stability constants of the actinium complexes Ac(X^–)²⁺, X^–=Cl^– or NO ₃ ^– , were determined. Our results show that actinium formed less stable complexes with Cl^– than with NO ₃ ^– ligands.     

Distribution of lanthanide and actinide elements between bis-(2-ethylhexyl)phosphoric acid and buffered lactate solutions containing selected complexants

With the renewed interest in the closure of the nuclear fuel cycle, the TALSPEAK process is being considered for the separation of Am and Cm from the lanthanide fission products in a next generation reprocessing plant. However, an efficient separation requires tight control of the pH which likely will be difficult to achieve on a large scale. To address this issue, we measured the distribution of lanthanide and actinide elements between aqueous and organic phases in the presence of complexants which were potentially less sensitive to pH control than the diethylenetriaminepentaacetic (DTPA) used in the process. To perform the extractions, a rapid and accurate method was developed for measuring distribution coefficients based on the preparation of lanthanide tracers in the Savannah River National Laboratory neutron activation analysis facility. The complexants tested included aceto-, benzo-, and salicylhydroxamic acids, N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), and ammonium thiocyanate (NH₄SCN). The hydroxamic acids were the least effective of the complexants tested. The separation factors for TPEN and NH₄SCN were higher, especially for the heaviest lanthanides in the series; however, no conditions were identified which resulted in separations factors which consistently approached those measured for the use of DTPA.     

Extraction equilibrium of indium(III) from nitric acid solutions by di(2-ethylhexyl)phosphoric acid dissolved in kerosene

The extraction equilibrium of indium(III) from a nitric acid solution using di(2-ethylhexyl) phosphoric acid (D2EHPA) as an acidic extractant of organophosphorus compounds dissolved in kerosene was studied. By graphical and numerical analysis, the compositions of indium-D2EHPA complexes in organic phase and stoichiometry of the extraction reaction were examined. Nitric acid solutions with various indium concentrations at 25 °C were used to obtain the equilibrium constant of InR? in the organic phase. The experimental results showed that the extraction distribution ratios of indium(III) between the organic phase and the aqueous solution increased when either the pH value of the aqueous solution and/or the concentration of the organic phase extractant increased. Finally, the recovery efficiency of indium(III) in nitric acid was measured.     

Extraction of lanthanoids and some associated elements by mono-(2-ethylhexyl)phosphoric acid and their separations

Mono-(2-ethylhexyl)phosphoric acid (H₂MEHP) has been used to study the extraction of some lanthanoids and other associated elements from nitric acid medium. Effect of various variables like kind of diluent, concentration of metal ion, nitric acid and extractant has been investigated. Based on distribution data, it was possible to achieve some separations of lighter lanthanoids from metals like titanium, zirconium, thorium and uranium with high separation factors.     

Enantioseparation of amino acids by co-extractants with di(2-ethylhexyl)phosphoric acid and tartaric acid derivatives

A co-extraction method using di(2-ethylhexyl)phosphoric acid (D2EHPA) with each of the two tartaric acid derivatives, O,O′-dibenzoyl-(2S,3S)-tartaric acid [(+)-DBTA] and O,O′-dibenzoyl-(2S,3S)-4-toluoyl-tartaric acid [(+)-DTTA] was developed for the enantioseparation of four amino acids: racemic tryptophan (rac-Trp), racemic phenylalanine (rac-Phe), racemic p-hydroxyphenylglycine (rac-Hpg) and racemic tyrosine (rac-Tyr). The extractants were prepared in various proportions and diluted in n-octanol. The influence of the extractant composition, concentration of amino acid enantiomers, molecular structure of the solutes and extractive equilibrium temperature were studied. The maximum enantioselectivities of the four amino acids were 4.02, 1.37, 1.52 and 2.06 for Trp, Phe, Hpg and Tyr, respectively. The effects of the molecular structure of the solutes and amino acids along with the equilibrium temperature on the distribution ratio and enantioselectivity were examined, which is helpful for optimizing the extraction systems and realize the large-scale production of pure enantiomer.     

Determination of cerium in fission products by extraction with di(2-ethylhexyl)phosphoric acid

Summary The extraction of cerium, oxidized to the tetravalent state, from nitric acid medium by di(2-ethylhexyl)phosphoric acid in hexane was studied. The effect of nitric acid concentration, agent concentration, oxidizer amount, and carrier concentration on the yield of cerium extraction was investigated and the optimum conditions of the extraction were found. Under these conditions, the reproducibility of the method was determined and the extraction of other fission products (Sr, Cs, Zr, and Ru) was also tested. The procedure was verified by the determination of cerium in artificial and real mixtures of fission products.

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Zusammenfassung Es wurden Untersuchungen angestellt über die Extraktion von vierwertigem Cer aus salpetersaurer Lösung mit Hilfe von Di-(2-äthylhexyl)-phosphorsäure in Hexan. Im einzelnen wurde der Einfluß der Konzentration an Salpetersäure, Reagens, Oxydationsmittel und Träger auf die Extraktionsausbeute geprüft und die optimalen Bedingungen festgelegt. Weiterhin wurde die Reproduzierbarkeit des Verfahrens bestimmt und bei der Anwendung auf künstliche und natürliche Gemische von Spaltprodukten das Verhalten der anderen Elemente (Sr, Cs, Zr, Ru) untersucht.

     

Adsorption of lanthanides(III) from aqueous solutions by fullerene black modified with di(2-ethylhexyl)phosphoric acid

Fullerene black (FB) - a product of electric arc graphite vaporization after extraction of fullerenes - was modified with the di(2-ethylhexyl)phosphoric acid (D2EHPA). The distribution of D2EHPA between FB and aqueous HNO₃ solutions has been studied. The effect of HNO₃ concentration in the aqueous phase and that of D2EHPA concentration in the sorbent phase on the adsorption of microquantities of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y nitrates from HNO₃ solutions by D2EHPA-modified FB are considered. The stoichiometry of the sorbed complexes has been determined by the slope analysis method. The efficiency of lanthanides’ adsorption increases with an increase in the element atomic number. A considerable synergistic effect has been observed upon the addition of the neutral bidentate tetraphenylmethylenediphosphine dioxide ligand to D2EHPA in the sorbent phase.      

Extraction recovery of vanadium(IV) from acid sulfate solutions with di-(2-ethylhexyl)phosphoric acid

Extraction of vanadium(IV) with di-(2-ethylhexyl)phosphoric acid from acid sulfate solutions in the presence of sodium sulfate was studied. The composition of the complex being extracted was found, and the equation of the extraction reaction was determined. The equilibrium constant of the reaction by which vanadium(IV) is extracted with di-(2-ethylhexyl)phosphoric acid was found by taking into account the complexation of vanadium(IV) in acid sulfate solutions.     

Extraction of amino acids with di(2-ethylhexyl)phosphoric acid in the presence of dicyclohexyl-18-crown-6

Extraction of amino acids from aqueous solutions into chloroform with di(2-ethyl-hexyl)phosphoric acid was studied. The extraction efficiency decreases in the sequence Trp>Phe>Leu>Arg>Lys>He>Ala>Gly. The addition of dicyclohexyl-18-crown-6 improves the efficiency and kinetics of extraction of most amino acids. The extraction degree depends on the concentration of the crown ether. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 952–955, May, 2000.     

Extraction of neodymium and europium by bis-(2-ethylhexyl) phosphoric acid from aqueous diamine solutions

The extraction of Nd³⁺ and Eu³⁺ from aqueous media containing selected diamine ligands by HDEHP solution in benzene has been investigated. It is found that the presence of the diamine in the aqueous phase enhances the extraction of both Nd³⁺ and Eu³ in the organic phase. The possible explanation for this behaviour is presented and a mechanism based on extraction of an adduct of the type MH₃(DEHP)₆. B is found to be the most probable.     

Solvent extraction of Fe(III) by di-(2-ethylhexyl)phosphoric acid from phosphoric acid solutions

The extraction of iron(III) from aqueous phosphoric acid was studied using di-(2-ethylhexyl)phosphoric acid and trioctylphosphine oxide in nonaromatic hydrocarbon diluent. Distribution ratios have been investigated as a function of concentration of iron(III), phosphoric acid concentration, extractant concentration and extraction temperature. The apparent enthalpy change for the extraction reaction has been calculated from the temperature dependence data. It was found that the extractant dependency for iron(III) is first power indicating hydrolysis of iron(III) in the aqueous phase.     

Recovery of manganese(II) by electrodialysis with liquid membranes based on di(2-ethylhexyl)phosphoric acid

Electrodialysis membrane extraction of manganese(II) from sulfuric acid solutions with liquid membranes containing di(2-ethylhexyl)phosphoric acid and tri-n-octylamine in 1,2-dichloroethane was studied. The effect of the electrodialysis conditions and the composition of the organic phase and aqueous solutions on the transport rate of manganese(II) ions was examined. The conditions of quantitative recovery of the metal from a 0.01 M MnSO₄ solution were determined.     

Radiation effects on the extraction of americium(III) with di(2-ethylhexyl) phosphoric acid

Radiation effects on the extraction of Am(III) with di (2-ethylhexyl) phosphoric acid (DEHPA) was studied by exposing DEHPA to gamma rays under various conditions. Gamma irradiation of undiluted DEHPA causes an enhancement of extraction of Am(III) due to the formation of mono (2-ethylhexyl) phosphoric acid (MEHPA) similarly to that of Nd(III). The presence of diluent during irradiation brought about a slight difference from the results in the absence of a diluent. The marked change occurred in Df when the organic solvent was exposed to γ-ray while being mixed with nitric acid solution. An initial slight increase of Df for Am(III) and Nd(III) was followed by a subsequent decrease beyond an absorbed dose of approximately 200 Wh·1⁻¹. This phenomenon was explained by the enhanced decomposition of DEHPA and the subsequent strong hydrolytic and radiolytic decomposition of MEHPA to H₃PO₄ in the aqueous phase, and the complex forming nature of H₃PO₄ with Am(III) and Nd(III).     

Studies on the solvent extraction behaviour of Pu(IV) from sulfuric acid medium into di-2-ethylhexyl phosphoric acid (HDEHP)

Extraction of plutonium(IV) from aqueous sulfuric and sulfuric-nitric acid into di-2-ethylhexyl phosphoric acid (HY) in the diluents n-dodecane, toluene or chloroform has been investigated. The composition of the Pu(IV) species extracted from H₂SO₄ was found to be PuH₂Y₆, which changed to Pu(NO₃)H₂Y₅ and Pu(NO₃)₂H₂Y₄ with increasing concentration of nitrate ion in the aqueous medium. These three species can be represented as PuY₂(HY₂)₂, Pu(NO₃)Y(HY₂)₂ and Pu(NO₃)₂(HY₂)₂, respectively, where Y represents the anion of monomeric HY, and HY₂ the anion of dimeric H₂Y₂. Synergism in the extraction of Pu(IV) by the addition of thenoyltrifluoroacetone (HTTA) to HY was also investigated and attributed to extraction of the additional species, Pu(TTA)Y(HY₂)₂ and Pu(TTA)₂(HY₂)₂. The addition of the neutral extractant tri-n-octylphosphine oxide (TOPO) to HY did not result in synergism in the extraction of Pu(IV) from aqueous sulfuric acid. With aqueous nitric acid under similar conditions, however, synergism was observed. The possible equilibria in these systems were identified and the corresponding equilibrium constants were determined.