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The extraction of aluminium from dilute phosphoric acid with di-2-ethylhexyl phosphoric acid (DEHPA) was optimized using response surface methodology. The optimization was based on the experimental three-level central composite face-centred design (CCF) and was conducted on real-life samples. The three variables included were pH, extractant concentration and aqueous to organic phase ratio (AO). Under the optimized conditions (pH 2.5, 0.6 M DEHPA and AO ratio 1:2), extraction efficiency of 99% for aluminium in four extraction stages is achieved. The purified phosphoric acid solution can then be utilized by the fertilizing industry. Stripping tests for organic phase loaded with aluminium were conducted with sulphuric acid. Extremely high stripping efficiency was obtained with 0.9 M sulphuric acid resulting in the recovery rate of 88% in one stage. After stripping, the aluminium sulphate solution can be reused as a precipitation agent for phosphorus in the wastewater treatment process.

Solvent extraction of rare earths from nitrate leach liquor of apatite using mixtures of tributyl phosphate (TBP) and di-(2-ethylhexyl) phosphoric acid (D2EHPA) was studied. The effects of nitrate and hydrogen ion concentration of the aqueous phase as well as the composition and concentration of extractants in the organic phase on the extraction behavior of lanthanum, cerium, neodymium, and yttrium were investigated. The distribution ratio of REEs increases by increasing the nitrate concentration in aqueous phase and concentration of extractants in organic phase, but the hydrogen ion concentration in aqueous phase has a decreasing effect. Yttrium as a heavy rare earth is more sensitive to these parameters than light rare earth elements. Although the composition of organic phase has a minor effect on the extraction of light rare earths, the percent of extraction of yttrium decreases dramatically by increasing the TBP content of organic phase. Mixtures of TBP and D2EHPA can show either synergism or antagonism extraction depending on the concentration and composition of extractants in organic phase. The best condition for separating rare earth elements in groups of heavy and light REEs can be achieved at high nitrate concentration, low H+ concentration, and high concentration of D2EHPA in organic phase. Separation of Ce and La by TBP and D2EHPA is practically impossible in the studied conditions; however, low nitrate concentration and high hydrogen ion concentration in aqueous phase and low concentration of extractants in organic phase favor the separation of Nd from other light rare earth elements.

Copper extraction from malachite ore by leaching and solvent extraction was examined. The leaching experiments were performed by sulphuric acid, hydrochloric acid and mixed reagent system. The iron impurity in the leach liquor had adverse effects on the copper extraction, therefore, iron separation from sulphate and mixed sulphate/chloride leach liquors was done using Tri-n-butyl-phosphate (TBP) and methyl-iso-butyl-ketone (MIBK). This indicated that it was possible to remove more than 95 % of iron content using 70 % TBP and 30 % MIBK. After iron removal, copper extraction was performed for various temperatures at different pH values from aqueous acetate buffer solutions with di-(2-ethylhexyl) phosphoric acid 20 % (V/V) dissolved in hexane. The results indicated that acetate ion had the maximum effect at pH 4.5. Thus, it could be mentioned that pH was the most important factor and that it was possible to recover more than 90 % of the copper from leach liquor under the optimum leaching condition.

The preparation of nuclear-grade zirconium and hafnium is very important for nuclear power. The separation of hafnium from zirconium in a hydrochloric acid solution by solvent extraction was investigated with di(2-ethylhexyl)phosphoric acid (D2EHPA). The effects of hydrochloric acid concentration, extractant concentration, diluents, and temperature on the distribution coefficient of hafnium and zirconium were studied. The species extracted were ZrOA2·2HA and HfOA2·2HA. In this process, the separation factors varied with different diluents and followed the order octane > hexane > toluene > chloroform. A high separation factor value of 4.16 was obtained under the conditions of a solution containing 0.05 mol/L HCl and 0.01 mol/L D2EHPA for the separation of hafnium from zirconium. The extraction reaction was endothermic.

Separation of trivalent lanthanides (Ln(III)) and actinides (An(III)) is a key issue in the advanced spent nuclear fuel reprocessing. In the well-known trivalent actinide lanthanide separation by phosphorus reagent extraction from aqueous komplexes (TALSPEAK) process, the organophosphorus ligand HDEHP (di-(2-ethylhexyl) phosphoric acid) has been used as an efficient reagent for the partitioning of Ln(III) from An(III) with the combination of a holdback reagent in aqueous lactate buffer solution. In this work, the structural and electronic properties of Eu3+ and Am3+ complexes with HDEHP in nitric acid solution have been systematically explored by using scalar-relativistic density functional theory (DFT). It was found that HDEHP can coordinate with M(III) (M=Eu, Am) cations in the form of hydrogen-bonded dimers HL2 - (L=DEHP), and the metal ions prefer to coordinate with the phosphoryl oxygen atom of the ligand. For all the extraction complexes, the metal-ligand bonds are mainly ionic in nature. Although Eu(III) complexes have higher interaction energies, the HL2 - dimer shows comparable affinity for Eu(III) and Am(III) according to thermodynamic analysis, which may be attributed to the higher stabilities of Eu(III) nonahydrate. It is expected that this work could provide insightful information on the complexation of An(III) and Ln(III) with HDEHP at the molecular level.

The presence of calcium and magnesium affects the purity of the final product MnCl2 in hydrometallurgical treatment processes. The solvent extraction method can be used to separate Ca2+ and Mg2+ from Mn2+ solutions containing impurity ions such as Ca2+ and Mg2+. This article aims to investigate the single-stage extraction equilibrium of Ca2+, Mg2+, and Mn2+ in chloride medium using di(2-ethylhexyl)phosphoric acid in kerosene (O:A = 1:1). The results show that the pH0.5 values are 1.11, 1.56, and 2.18 for Ca2+, Mn2+, and Mg2+, respectively. The mechanism of extraction and stoichiometries of metal-containing extracted species were illustrated based on a slope analysis. The composition of the extracted species in the organic phase is proposed to be MnR2·R2H2, CaR2·R2H2, and MgR2·(R2H2)2, respectively.

This paper reports on the supported liquid membrane (SLM) based transport studies of U(VI) from sulphate medium using di-(2-ethylhexyl) phosphoric acid/n-dodecane as carrier. Polytetrafluoroethylene membrane was used as solid support and H2SO4 as receiver phase. The effects of various parameters such as receiver phase concentration, feed acidity, carrier concentration, U(VI) concentration, membrane thickness and membrane pore size on U(VI) transport had been investigated. With increase in H2SO4 concentrations and pH of feed solution there is an increase in U(VI) transport across the SLM. Similarly with increase in membrane thickness the U(VI) transport decrease whereas in case of pore size variation reverse results are obtained. The membrane thickness variation results showed that the U(VI) transport across the SLM is entirely diffusion controlled and the diffusion coefficient the D (o) was calculated as 1.36 × 10−7 cm2 s−1. Based on optimized condition, a scheme had been tested for selective recovery of U(VI) from ore leach solution containing a large number of other metal ions.

To go through the first stage of industrial solvent extraction process in order to recover uranium from phosphate rocks by liquid membrane techniques, as a simple model, the kinetics of facilitated transport of uranium(VI) from a dilute phosphoric acid medium into more concentrated phosphoric acid media as a receiving phase through a bulk liquid membrane containing di-2-ethylhexyl phosphoric acid as a carrier was studied. The influence of phosphoric acid concentration in the source and receiving phases, carrier concentration, type of solvent, stirring speed and temperature were investigated. The kinetic parameters (k e, k s, t max, J max) were calculated for the interface reactions assuming two consecutive, irreversible first-order reactions. The activation energy values were calculated as 29.40 and 19.51 kJ mol−1 for extraction and stripping, respectively. The values of calculated activation energy indicated that both the extraction and stripping processes were controlled by mixed regime (both kinetic and diffusion). In addition, the influence of adding trioctyl-phosphine oxide into the membrane phase as a synergic agent on the transport kinetics was determined.

The synergistic effect of five 8-quinolinol derivatives (HQs) on the extraction of gallium(III) with di(2-ethylhexyl)-phosphoric acid (D2EHPA or HA) from weak nitric acid into supercritical carbon dioxide (SC-CO(2)) was investigated. 8-Quinolinol (Hq), 5-ethoxymethyl-8-quinolinol (HO(2)q), 5-hexyloxymethyl-8-quinolinol (HO(6)q), 5-(2,2,2-trifluoroethoxymethyl)-8-quinolinol (HFO(2)q), and 5-chloro-8-quinolinol (5-Cl-Hq) were used as synergists. Synergism was observed for all of the HQs. The synergistic effect increased in the following order: Hq < HO(2)q < HFO(2)q < 5-Cl-Hq ≍ HO(6)q. The extent of synergism can be related to both the distribution constant and the acid dissociation constant of the HQ. The synergistic extraction equilibrium of gallium(III) with D2EHPA and 5-Cl-Hq into SC-CO(2) was investigated; the results suggest that the composition of the extracted complex is as GaA(2)Q·HA. The synergistic extraction mechanism was the same for both SC-CO(2) and n-heptane. The synergistic extraction equilibrium constants in both cases were calculated based on the experimental results.

The use of a microfluidic device in determining the extraction kinetics of CoII ions by di-(2-ethylhexyl) phosphoric acid (DEHPA) was demonstrated. Experimental data obtained using a Y-Y-shaped microchannel were modelled using a finite volume method. The contributions of diffusion and reaction transport resistances to the overall rate of mass transfer were obtained. A diffusion-controlled transfer assumption could not account for the experimental data, confirming that transport occurs under a mixed reaction–diffusion resistance regime. The reaction rate constant was determined to be $$(2.4 \pm 0.6) \times 10^{-10}$$ m/s, in good agreement with corresponding Lewis cell measurements from the literature.

The extraction of Mg2+ from ammonium dihydrogen phosphate (MAP) solution by extractant (D2EHPA) and its mixture, including acidic extractant (HEHPEHE), alkaline extractant (TOA) and neutral extractant (TBP) respectively, is investigated. The good extraction selectivity of Mg2+ with D2EHPA from ammonium dihydrogen phosphate solution is verified, which is found to be associated with the cation exchange and chelation capability of D2EHPA on the basis of its molecular structure. The related thermodynamic data are also obtained in terms of experimental results as follows: the extraction enthalpy is 2.659×10−2 (J·mol−1·K−1), the free energy is 1.501×103 (J·mol−1) and the entropy is 4.441 (J·mol−1). Meanwhile, the major influencing factors, such as the initial pH, the initial concentration of extractant, phase ratio and the extraction temperature on the extraction ratios of Mg2+, are studied, and the optimal process conditions are obtained. As shown in the extraction experiments for practical MAP solution, superior grade MAP can be obtained by three levels of extraction under optimal condition.

The extraction of rare earths from nitrate medium using three organophosphorus acids, 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (HEHEHP), di-(2-ethylhexyl) phosphoric acid (D2EHPA), bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex272), and their mixtures with sec-octylphenoxy acetic acid (CA12) has been studied in detail. The mixtures have different extraction effects on various rare earths. Synergistic extraction effects are only found when light rare earths and yttrium (III) are extracted with mixtures of D2EHPA and CA12. The possibilities of separating the rare earths with these mixtures are investigated according to the extractabilities. It is feasible and advantageous to separate yttrium (III) from the lanthanoids (III) with HEHEHP + CA12 and D2EHPA+CA12 mixtures at proper extractant ratios. The separation of yttrium (III) from heavy rare earths is also possible with mixtures of Cyanex272 and CA12.

An emulsion liquid membrane (ELM) con- taining di-2-ethylhexylphosphoric acid (D2EHPA) as the carrier extractant and SPAN 80 as the surfactant was used to pre-concentrate Am 3? from dilute acid solutions. Effects of various factors such as: external phase pH, internal phase conditions, equilibration time, D2EHPA concentra- tion, SPAN 80 concentration, etc. on Am 3? mass transfer were investigated. Emulsion was broken by the addition of solvents such as acetone and the actual mass transfer obtained after breaking the emulsion agreed well with that obtained by the difference method.

The molecular interactions in the complex formation of two tartaric acid derivatives with di(2-ethylhexyl) phosphoric acid are investigated. The complex formation with a 1:1 stoichiometry between tartaric acid derivatives and D2EHPA can be obtained through UV-Vis titration, NMR chemical shifts and molecular dynamic simulations. Furthermore, the differences of the two complexes on the binding constants and strength of hydrogen bonds can also be determined. Such research will ideally provide insight into ways of regulating the complex forming properties of tartaric acid derivatives for composing or synthesizing new chiral resolving agents.

Neodymium-di-(2-ethylhexyl) phosphoric acid (DEHPA) species forming in the organic phase during solvent extraction of neodymium with solutions of DEHPA have been studied. Two samples were prepared: one with a low molar ratio of neodymium to DEHPA, which is liquid and clear, and the other with a high molar ratio of neodymium to DEHPA (complete loading), which has the consistency of a gel. Electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) mass spectrometric investigations show numerous compounds, in addition to the generally assumed species dimeric DEHPA and Nd(DEHP-DEHPA)3, in the liquid sample. The nuclear magnetic resonance (NMR) spectroscopic investigation of pure DEHPA and of completely loaded sample confirm the formula of pure DEHPA and of the organic part of Nd(DEHP)3. Furthermore, chemical analysis of a dried, completely loaded sample also proves the existence of the species Nd(DEHP)3. Results of X-ray powder diffraction measurements of this sample agree well with literature data.

Separation of copper(II) and platinum(IV) in extraction from binary acid chloride solutions with liquid membranes containing technical-grade di(2-ethylhexyl)phosphoric acid with addition of tri-n-octyl amine in 1,2-dichloroethane under the conditions of the galvanostatic electrodialysis was studied. The influence exerted by the current density and composition of aqueous solutions and liquid membranes on the rate and selectivity of copper(II) extraction was analyzed. The optimal conditions of metal separation were determined.

The pertraction of dysprosium (Dy) through a supported liquid membrane (SLM) system consisting of PTFE (polytetrafluoroethylene) support, D2EHPA (di-2-ethylhexyl phosphoric acid) dissolved in kerosene as membrane solution, and HNO3 solution as stripping solution, was studied. The experiments were designed by the Taguchi method in order to investigate the effects of initial Dy concentration, feed phase pH, different stripping solution concentration, and D2EHPA concentration in the membrane phase on Dy pertraction. Optimal experimental conditions for Dy pertraction were obtained using an analysis of variance (ANOVA) (feed concentration: 130 mg L−1, D2EHPA concentration: 0.90 M, feed phase pH: 5, stripping phase concentration: 2 M). In addition, the stability of the carrier in terms of its leaching from the membrane support was studied over a period of 6 days and was found to be satisfactory over that time.

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.

The selective transport of yttrium(III) in the presence of iron(III) through a supported liquid membrane (SLM) has been investigated by using di(2-ethylhexyl)phosphoric acid (DEHPA) as a mobile carrier. Yttrium(III) with fast kinetics was preferentially transported from the feed solution of dilute acid into the product solution of 1M H2SO4, while most of iron(III) with slow kinetics remained in the feed solution. The effective separation of yttrium(III) from a large amount of iron(III) was accomplished by the selective transport of yttrium(III) through the SLM.

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.

Structure and aggregates formed from cobalt-di(2-ethylhexyl)phosphoric acid (Co-HDEHP) complexes in solvent extraction systems were investigated by FT-IR, UV-Vis and photon correlation spectroscopic (PCS) techniques. Results showed that the Co-HDEHP complex displayed a dehydrated tetrahedral coordination structure of the chelate type inn-heptane and the aggregates were rather small. The addition of co-surfactant to the solvent produced a series of effect on the physicochemical nature of the molecular aggregates. In the presence of 2-octanol, a partially hydrated octahedral coordination structure was formed in equilibrium with the dehydrated tetrahedral structure for the Co-HDEHP aggregates in the organic phase and the equilibrium was found to be affected by the ionic strength of the aqueous phase. Furthermore, the FT-IR results showed that Co-HDEHP complex in the presence of 2-octanol displayed a bridge-coordination between the cobalt and the extractant molecules.

It was found that the main ionogenic radiolytical degradation products of tributylphosphate were monobutylphosphate dibutylphosphate, phosphoric acid, formic, acetic, propionic and butyric acids as the result of gamma-irradiation of two-phase water-tributylphosphate system. In the case of irradiation of two-phase water-di(2-ethylhexyl)-phosphoric acid system, the main radiolytic degradation products are 2-ethylhexylphosphoric acid and phosphoric acid. All products were determined using isotachophoresis. According two-phase theory the total and partial radiation yields of products were calculated from the results.

The extraction of Na3+, Eu3+ and Tm3+ by di-(2-ethylhexyl)phosphoric acid, HDEHP has been studied from various aqueous acidic solutions. The extraction of these elements is inversely proportional to the third power of the hydrogen ion concentration. Antagonistic effects were observed when the extraction was studied by mixtures of HDEHP and tributyl phosphate, TBP, or trioctylphosphine oxide, TOPO. The presence of water-miscible alcohols and acetone generally increases the extraction of these three elements from HCl solutions. Reaction mechanisms have been suggested and discussed in the light of the data obtained.

The aggregation equilibria of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH(EHP)) and di(2-ethylhexyl)phosphoric acid (HDEHP) dissolved in toluene has been investigated by vapor-pressure osmometry at different temperatures. The experimental data have been treated both graphically and numerically, and the average aggregation number n of organophosphorus acids, as well as the aggregation constants, has been determined. The results suggest that dimers are formed and the dimerization constant decreases with temperature. Finally, an estimated enthalpy value for the aggregation of organophosphorus acids in toluene has been calculated by using the van′t Hoff equation.

The extraction of uraninm(VI) from an aqueous HNO 3 phase into an organic phase consisting of a polyurethane foam immobilizing a solution of di(2-ethylhexyl)phosphoric acid (HDEI-1P) 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(IID from acidic perehlorate solutions of constant ionic strength.

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.

Except for conditions of low acidity and low ratios of di(2-ethylhexyl) phosphoric acid (HDEHP) to U(VI) the data obtained for the distribution of U(VI) between sulfuric acid solutions and polyurethane foams loaded with solutions of HDEHP in nitrobenzene could be analyzed

The extraction of cerium (III) from weakly acidic chloride solutions by HDEHP-nitro-benzene-loaded polyurethane foams could be analyzed quantitatively

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.

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.

The extraction of actinium by HDEHP solutions in n-heptane as a function of mineral acids and some lanthanides (Ln) in the aqueous phase has been studied. It was found that the actinium extraction coefficient in the absence of Ln decreased linearly with acid concentration with the slope of −3 in the whole investigated range of its concentration. In the presence of Ln the extraction coefficient decreased with a smaller slope than in the absence of Ln. This slope decreased with the Ln salt concentration. The extraction coefficient of Ac decreased with a slope of −3 at acid concentrations above 0.1N, regardless of the Ln concentration in the extraction system.

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.

The equilibrium data show that indium can be quickly extracted from acidic aqueous solutions by di-(2-ethylhexyl)phosphoric acid in methyl isobutyl ketone. In this polar solvent the species ML3·HL is extracted. The overall extraction constant is higher than that for other tervalent metals. The extraction process can be combined with AAS determination of the indium. The method is fast because stripping is not necessary, and the organic phase can be analysed directly by AAS. Use of a 5∶1 v/v aqueous: organic phase ratio increases the sensitivity. In the pH-range used the method has good selectivity.

In order to clarify the influence of radiation degradation of DEHPA upon the extraction of lanthanides, the extraction of neodymium(III) was studied using DEHPA, MEHPA, 2-ethylhexanol and γ-ray irradiated DEHPA. The most significant effect of DEHPA radiolysis on the extraction was found to be the enhacement of extraction capability mainly due to the primary radiolysis product MEHPA. 2-Ethylhexanol, another radiolysis product, showed a depressant effect on DEHPA-Nd(III) extraction. However, the mixture of MEHPA and 2-ethylhexanol improved the extraction. The mixed solvent DEHPA-MEHPA was found to be more effective than the individual components for lanthanide extraction.

The following extraction systems have been studied: (Ce3++Eu3+) (NO3)-(EDTA, DCTA, DTPA)/TBP in n-alkane and (Ce3++Eu3+)(NO3)/DEHPA in n-alkane at concentration ratios as follows: [Ce3+]=trace −1 mol·dm−3, [Eu3+]=trace −0.1 mol·dm−3. [TBP]=(0.183−1.83) mol·dm−3, [DEHPA]=(5·10−3−0.1) mol·dm−3, [(H, Na)NO3]=(0.1−6) mol·dm−3, [Eu3+]: [EDTA, DCTA, DTPA]=1∶1−1∶10. The initial concentration of Eu3+ in aqueous phase in the extraction system containing a mixture of Ce3+ and Eu3+ was trace, 1% and 10% compared with the Ce3+ concentration. The distribution of the elements between the phases was observed radiometrically using141Ce,152Eu and154Eu. The results are documented by the distribution ratios DCe, DEu and separation factor α=DEu/DCe as functions of variable parameters of the systems.

A mass spectrometric study on DEHPA was carried out and compared with radiolysis data on DEHPA for γ-irradiation in the liquid phase. The mass spectra of DEHPA show an extremely low intensity of parent ion and the presence of double rearrangement ions of (RO)P(OH)3+ and P(OH)4+, where R is the 2-ethylhexyl group. The appearance potentials of the principal ions in the mass spectrum were determined and the dissociation processes of DEHPA in the phase discussed. The fragment ions show good agreement with the results in the liquid phase where the mono-ester, orthophosphoric acid, octane and heptane were formed by the dealkylation, however, the peak intensities of some fragment ions in the mass spectrum differ from the radiolytic yields of the corresponding products. These differences imply the significant role of neutralization and recombination reactions in the liquid phase radiolysis.

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.

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).

An elution scheme has been developed for obtaining separate fission product and uranium fractions using extraction chromatographic techniques with di-(2-ethylhexyl)phosphoric acid as a stationary phase and HCl of varying concentration as eluting agent. The investigations have been concentrated on the fission products cerium, europium, molybdenum and zirconium. The elution of zirconium by oxalic acid is characterized by a peak broadening and has been explained by considering extraction kinetics. Experiments on column performance with different support materials have proved Ftoroplast-4 and Celite Hyflo Super Cel to be capable of giving column fillings with equal separation ability.

The radiolysis of di(2-ethylhexyl)phosphoric acid causes deterioration of the extraction of Sr(II) at about pH 5. This effect is attributed to the main radiolysis product, mono(2-ethylhexyl)phosphoric acid. However, MEHPA shows an ability of extracting Sr(II) in an acid medium. The presence of TBP prevents MEHPA from extracting Sr(II) in acidic solutions. The decrease of Df due to γ-irradiation is almost consistent with that estimated from the G values for the decomposition of DEHPA and formation of MEHPA. The diluent effect of radiolysis on the extraction was also determined.

A solvent extraction procedure for the separation of niobium and tantalum has been developed. The method consists of extracting tantalum from its aqueous mixture with niobium, with the help of di(2-ethylhexyl)phosphoric acid (HDEHP) in n-heptane. The aqueous feed consists of niobium and tantalum in an aqueous medium containing hydrochloric and oxalic acids. The concentrations of niobium and tantalum were raised to 1 mg/ml in the aqueous solution. The extraction efficiency of tantalum under these conditions was found to be ∼85%. Effects of chloride and oxalate ions as well as those of the concentration of HDEHP on the extraction efficiency were studied and discussed in detail.

The extraction equilibria of the lanthanide chloride systems MC13-HC1-H2O-1 M D2EHPA (in mineral spirits), where M designates Sm, Nd, and trivalent Ce cations, was studied over an extensive range of concentrations. The metal aqueous concentration was varied from 0.05 to 2.0 M and the aqueous acidity ranged from 0.3 to 1.0 M. The equilibrium curves, with the aqueous acidity as a parameter, exhibit a behavior typical of other lower lanthanides. Further, trivalent cerium behaves the same as other trivalent rare earths. A study of the binary extraction systems Sm-Nd, Sm-Ce, and Nd-Ce indicate that the separation factor remained nearly constant for all conditions studied. The arithmetic averages were βsm.Nd ∼ 8.4, βNd.Ce ∼ 2.0, and βsm.Ce∼ 18.9. In the ternary system Sm-Nd-Ce, the separation factor of each combination pair of elements remained essentially constant for all conditions studied. Furthermore, the separation factor of each pair of elements in the ternary system remained the same as in the case where each pair of elements is extracted together.

The extraction of yttrium from the system YCl3-Di(2-ethylhexyl) phosphoric acid (D2EHPA) has been reported previously.1,2 The extraction equilibrium in the system Y(NO3)3-HNO3-H2O-D2EHPA in Amsco as the solvent was studied as a function of the D2EHPA concentration, acidity and aqueous yttrium concentration, and the results were compared to the choride system. The ratio of the distribution ratios for nitrate and chloride system was found to vary from 0.5 to 7.0.