Extraction of micro- and macroconcentrations of rare earth ions with the mixture of D2EHPA and TBP in n-hexane and cyclohexane

The synergistic solvent extraction of Eu(III) and some other rare earth elements from nitrate solutions (HNO₃+LiNO₃) by a mixture of (TBP+D2EHPA) in n-hexane and cyclohexane has been investigated at 22 °C. Antagonism found in europium extraction from 0.1M HNO₃ transforms into a synergistic effect. The synergistic effects existing for all investigated metals in extraction from 0.1M HNO₃+3M LiNO₃ were caused by formation of mixed complexes of the type Ln(D2EHPA)_2nH_2n–3+1(NO₃)₁TBP_m, where 1=1 or 2. The selectivity of the extraction in a synergistic system is lower for the La–Yb pair than in the case of D2EHPA extraction under the same conditions. On the other hand, the application of the synergistic mixture is more suitable for Eu–Ho separation. Thus the synergistic effect can be used for the separation or refining of some lanthanides.     

Synergic extraction of lanthanoid(III) with 2-thenoyltrifluoroacetone and triphenylarsine oxide in benzene

The synergic extraction of La(III), Eu(III), and Lu(III) with 2-thenoyltrifluoroacetone (Htta) and triphenylarsine oxide (tpao) in benzene has been studied. The extractability of lanthanoids, Ln(III), is significantly affected by the association of Htta with tpao in the organic phase. The associated species is Htta·tpao and the association constant is determined as 10^1.63. The intrinsic extraction equilibrium of Ln(III) is analyzed using the free concentration of Htta and tpao. The synergic enhancement is ascribable to the formation of the adduct complexes shown as Ln(tta)₃tpao and Ln(tta)₃(tpao)₂ in the present extraction system. The adduct formation constants determined are very large as expected from the high basicity of tpao.     

Synergistic extraction of uranium(VI) and thorium(IV) with mixtures of Cyanex272 and other organophosphorus ligands

The extraction of thorium(IV) and uranium(VI) from nitric acid solutions has been studied using mixtures of bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex272 or HA), and synergistic extractants (S) such as tri-butylphosphate (TBP), tri-octylphosphine oxide (TOPO) or bis(2,4,4-trimethylpentyl)thiophosphinic acid (Cyanex301). The results showed that these metallic ions are extracted into kerosene as Th(OH)₂(NO₃)A·HA and UO₂(NO₃)A·HA with Cyanex272 alone. In the presence of neutral organophosphorus ligands TBP and TOPO, they are found to be extracted as Th(OH)₂(NO₃)A·HA·S and UO₂(NO₃)A·HA·S. On the other hand, Th(IV), U(VI) are extracted as Th(OH)₂(NO₃)A·HA·2S and UO₂(NO₃)A·HA·S in the presence of Cyanex301. The addition of neutral extractants such as TOPO and TBP to the extraction system enhanced the extraction efficiency of both elements while Cyanex301 as an acidic extractant has improved the selectivity between uranium and thorium. The effect of TOPO on the extraction was higher than other extractants. The equilibrium constants of above species have been estimated by non-linear regression method. The extraction amounts were determined and the results were compared with those of TBP. Also, it was found that the binding to the neutral ligands by the thorium–Cyanex272 complexes follows the neutral ligand basicity sequence.     

The effect of diluents on extraction of copper(II) with di(2-ethylhexyl)phosphoric acid

The liquid–liquid extraction of copper(II) from sulfate medium with di(2-ethylhexyl)phosphoric acid (D2EHPA, HL) at 25°C is studied with the following parameters: pH, concentration of the extractant, and the nature of diluent. The effect of the diluent using polar and nonpolar solvents in the extraction of copper(II) is discussed. The extracted copper(II) species were CuL₂ in 1-octanol and methyl isobutyl ketone and CuL₂ · 2HL in toluene, carbon tetrachloride, and cyclohexane. The extraction constants are evaluated for different diluents.     

Extraction of Lanthanide Nitrates in Multicomponent Aqueous-Organic Two-Phase Systems with D2EHPA

Lanthanum nitrate distribution in three-component aqueous-organic systems with D2EHPA from acetate or acetic acid–acetate solutions has been studied, it has been shown that variation in sodium acetate concentration or composition of CH₃COONa–CH₃COOH mixture can affect metal distribution ratios. It has been found that extraction in three-component mixture of 1: 1: 1 composition (aqueous solution Ln(NO₃)₃ + CH₃COONa + CH₃COOH–D2EHPA in hexane–isopropyl alcohol) can provide lanthanide separation, which is dependent on the ratio of sodium acetate and acetic acid in aqueous phase and on D2EHPA concentration in organic phase. Lanthanide–lanthanum separation factors have been calculated for the extraction of lanthanide nitrates from acetic acid–acetate solutions.     

Studies on mixed ligand complexes of samarium(III), europium(III) and dysprosium(III) with 1-nitroso-2-naphthol and trioctylphosphine oxide

The extraction behavior of Sm(III), Eu(III) and Dy(III) with 1-nitroso-2-naphthol (HA) and trioctylphosphine oxide (TOPO) in methyl isobutyl ketone (MIBK) from aqueous NaClO₄ solutions in the pH range 4–9 at 0.1M ionic strength has been studied. The equilibrium concentrations of Sm and Dy were measured using their short-lived neutron activation products,¹⁵⁵Sm and^165mDy, respectively. In the case of Eu, the concentrations were assayed through the^152,154Eu radiotracer. The distribution ratios of these elements were determined as a function of pH, 1-nitroso-2-naphthol and TOPO concentrations. The extractions of Sm, Eu and Dy were found to be quantitative with MIBK solutions in the pH range 5.9–7.5, 5.6–7.5 and 5.8–7.5, respectively. Quantitative extraction of Eu was also obtained between pH 5.8 and 8.8 with chloroform solutions. The results show that these lanthanides (Ln) are extracted as LnA₃ chelates with 1-nitroso-2-naphthol alone, and in the presence of TOPO as LnA₃(TOPO) and LnA₃(TOPO)₂ adducts. The extraction constants and the adduct formation constants of these complexes have been calculated.     

The intensity of spontaneous surface convection in di-(2-ethylhexyl)phosphoric acid systems

The dependence of the rate of the arising and evolution of spontaneous surface convection (SSC) on various effects during the extraction of rare-earth metals (REMs) with heptane (or toluene) solutions of di-(2-ethylhexyl)phosphoric acid (D2EHPA) (HA) was studied. The intensity of SSC in heptane was higher than in toluene systems. In the same solvent, it was higher for the elements from the cerium subgroup. At low concentrations of a REM salt in the starting aqueous solution, the modulus of the surface rate of liquid flow in the dynamic interphase layer (DIL) was high because low-solubility salt particles experienced sedimentation, and the interphase surface was renewed. It was concluded that, at higher REM concentrations in the aqueous phase, the modulus of the surface flow rate was considerably higher because of the accumulation of LnA₃ and structure formation in the interphase layer. For comparison, we give the moduli of surface flow rates of liquids during the re-extraction of acids in a toluene, HNO₃/water system, in which the rate is higher than in aqueous REM(III) salt/D2EHPA solution in an organic diluent. Original Russian Text ? N.F. Kizim, E.N. Golubina, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 7, pp. 1384–1390.     

Synergistic extraction behavior of samarium(III), europium(III) and dysprosium(III) with 1-nitroso-2-naphthol and 1,10-phenanthroline

The equilibrium extraction behavior of Sm(III), Eu(III) and Dy(III) from aqueous NaClO₄ solutions in the pH range of 4–9 at 0.1 M ionic strength into organic solutions of 1-nitroso-2-naphthol (HA) and 1,10-phenanthroline (Phen) has been studied. The equilibrium concentrations of Eu were assayed through the 344 keV photopeak of the¹⁵²Eu radiotracer used. The concentrations of Sm and Dy were measured by irradiating one mL portions of the organic extract and analyzing the 104 and 108 keV photopeaks of the short-lived neutron activation products,¹⁵⁵Sm and^165mDy, respectively. Quantitative extraction of Eu with 5×10^–2 M HA alone was obtained in the pH range of 6.7–7.8 with n-butanol, 7.4–8.5 with chloroform, 8.0–8.7 with ethyl acetate, 7.7–8.5 with isoamyl alcohol and 6.1–8.0 with methyl isobutyl ketone (MIBK). But, Eu was extracted only to a maximum of 78% and 83% in the pH range of 8.3–8.9 and 7.4–8.1 with carbon tetrachloride and xylene, respectively. The extraction of Sm and Dy were found quantitative in the pH range of 6.3–7.0 and 6.6–7.1, respectively, with 5×10^–2 M HA alone in MIBK solutions. The synergistic extraction of Eu was quantitative in the pH range of 6.6–9.8 with chloroform, 7.8–8.9 with ethyl acetate, 7.7–8.5 with isoamyl alcohol and 6.0–9.6 with MIBK when 1×10^–2 M each of HA and Phen were employed. Sm and Dy were quantitatively extracted into MIBK solutions containing 5×10^–2 M each of HA and Phen in the pH range 6.0–7.5 and 6.1–7.5, respectively. The distribution ratios of these lanthanides (Ln) were determined as a function of pH, and HA and Phen concentrations. The analysis of the data suggests that these Ln are extracted as LnA₃ chelates when HA alone is used. In the presence of HA and Phen, both LnA₃(Phen) and LnA₃(Phen)₂ adducts are formed only in the MIBK system while LnA₃(Phen) complexes are the predominant ones in all other solvent systems studied. The extraction constants and the adduct formation constants of these complexes have been calculated.     

Two-phase potentiometric metal extraction titrations of silver(I), copper(II) and cadmium(II) using some cation-exchangers as extractants

The use of two-phase potentiometric metal extraction titrations to study solvent extraction equilibria is described. The method provides a highly reproducible and convenient manner by which to determine extraction behaviour. The system was tested on a number of acidic extractants, namely D2EHPA, Ionquest 801, Cyanex 272, naphthenic acid and Versatic 10 acid. The extraction from an aqueous nitrate medium of silver(I), copper(II) and cadmium(II) was studied. The potentiometric data were used to obtain extraction curves and elucidate the nature of the extracted complexes by slope analysis and non-linear least squares treatment. In general, the following extraction order was obtained: D2EHPA > Ionquest 801 > Cyanex 272 and naphthenic > Versatic 10 for copper(II) and cadmium(II). Organophosphorus acids were shown to form complexes of the nature of Cu(HA(2))(2) with copper(II) and carboxylic acids formed dimeric complexes (CuA(2)(HA))(2). With cadmium octahedral complexes of the form CdA(2)(HA)(4) occurred. The extraction of silver(I) by Versatic 10 gave a dimeric complex (AgA(HA))(2). HA denotes the extractant in the acid form.     

Selective separation of trace nickel(II) and gold(I) ions via hollow fiber supported liquid membrane enhanced by synergistic extractants D2EHPA/TBP

This work presents the selective and simultaneous separation of nickel (Ni²⁺) and gold ([Au(CN)₂]⁻) ions, in trace amounts, from alkaline solution via hollow fiber supported liquid membrane (HFSLM) technique. HFSLM is challengingly carried out in real rinse wastewater generated by the ENIG plating process. The influence of various chemical parameters, including the type of extractant and their concentrations, molar ratios of mixed extractant as well as type of strippant, are also studied. The organophosphorus extractant mixtures of D2EHPA and TBP provide a synergistic effect for target Ni²⁺ ions but has an antagonistic effect as regards the extraction of non-target [Au(CN)₂]⁻ ions. Compared to other inorganic acids, HCl is seen to be the most suitable strippant for the selective stripping. Results demonstrate that percentages of extraction and stripping of Ni²⁺ ions achieved 85.7 and 83.2%, respectively. In contrast, percentages of extraction and stripping of non-target [Au(CN)₂]⁻ ions attained 15.6 and 1.94%.     

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.     

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.      

The Extraction of U(VI) with N-Octanoyl-2-Methylpiperidine in Toluene

A new extractant, N-octanoyl-2-methylpiperidine (OMPPD) has been synthesized. The extraction of U(VI) with N-octanoyl-2-methylpiperidine (OMPPD) in nitric acid has been studied. The dependence of the partition reaction of U(VI) on the concentrations of nitric acid, extractant, salting-out agent LiNO₃, and temperature has been studied. In the light of the results, the extraction mechanism is discussed. The synergistic extracted complexes may be presented as UO₂(NO₃)₂(OMPPD)₂ . The related thermodynamic functions were calculated.     

Synergistic solvent extraction of zirconium(IV)

The extraction of Zr(IV) by 2-thenoyltrifluoroacetone (TTA) in carbon tetrachloride from aqueous hydrochloric acid solutions is a slow process. The addition of a neutral extractant, di-n-pentyl sulfoxide (DPSO) enhances considerably the rate as well as the percentage of extraction. The species extracted appears to be ZrCl₂(TTA)₂·2 DPSO. An increase in temperature results in a further increase in the rate and percentage of extraction. Studies have also been carried out on the extraction of the metal by mixtures of various neutral extractants. Thermodynamic parameters associated with the formation of the synergistic adducts have been evaluated.     

Emulsion liquid membrane extraction of Ni(II) and Co(II) from acidic chloride solutions using bis-(2-ethylhexyl) phosphoric acid as extractant

An emulsion liquid membrane process using bis-(2-ethylhexyl) phosphoric acid (D2EHPA) to extract and separate Ni(II) and Co(II) from acidic chloride solutions is described. Liquid membrane consists of a diluent, a surfactant (Span 80), and an extractant (D2EHPA). Hydrochloric acid was used as the stripping solution. The important parameters governing the permeation of nickel and their effect on the separation process have been studied. These parameters are stirring speed, feed phase pH, surfactant concentration, extractant concentration, stripping phase concentration, phase ratio, initial concentration of metal, and treatment ratio. The optimum conditions have been determined. The separation factors of Ni(II) with respect to Co(II), based on initial feed concentration, have been experimentally determined. Furthermore, the extraction selectivity for Co(II) over Ni(II) has been improved by using D2EHPA during the initial minutes.     

Extraction of californium/III/ from aqueous pyrophosphate and tripolyphosphate solutions with D2EHPA

Extraction of californium/III/ with di-/–2-ethylhexyl/ phosphoric acid /D2EHPA/ in heptane from pyrophosphate media is almost quantitative between pH 4 and 5. From tripolyphosphate media, however, two to three extractions are needed in the pH range of 3–5 to isolate Cf³⁺ completely. Reextraction experiments show that 1M H₂SO₄ can back-extract Cf³⁺ completely while two to three reextractions with 5M HNO₃ can only separate californium/III/. Reverse phase partition chromatography experiments were performed to recover 300 g of californium/III/. From slope analysis of the extraction data the composition of the extracted species has been found to be Cf/H₂P₂O₇/A.HA and Cf/H₄P₃O₁₀/.A₂.2HA from pyrophosphate and tripolyphosphate solutions, respectively, where D2EHPA is abbreviated as /HA/₂.     

Synergistic extraction of uranium from acidic sulfate leach liquor using D2EHPA mixed with TOPO

Uranium extraction from sulfate leach liquor acid by D₂EHPA and TOPO mixture in kerosene was investigated. The effect of different factors affecting the extraction mechanism such as sulfate leach liquor acid, D₂EHPA and TOPO concentrations and temperature have been studied. The mathematical treatment for the obtained date suggested that the composition of synergistic extraction species is (UO₂(D)₂T). The logarithm of the apparent equilibrium constant, log Kex, of synergistic extraction reaction has been evaluated, to be 3.35 ± 0.1. The effect of temperature on extraction process was investigated and the apparent values of the thermodynamics parameters (?H, ?G and ?S) were 38.2 kJ/mol, ?19.1 kJ/mol and 192.5 J/mol respectively.     

Extraction of uranium(VI) with bis(octylsulfinyl)methane

The liquid-liquid extraction of uranium(VI) from aqueous nitric acid with bis(octylsulfinyl)methane (BOSM) has been studied over a wide range of conditions. The extracted species appear to be UO₂(NO₃)₂·2BOSM. It was found that the extraction increased with increasing nitric acid concentration up to 8.5 mol/l and then descreased. Extraction also increased with increasing extractant concentration. The influence of temperature and salting-out agent concentration on the extraction equilibrium has also been investigated, and the enthalpy of the extraction reaction was estimated.     

The Extraction of Uranium(VI) with n-Octyldecylsulfoxides (ODSO)-Toluene

The liquid-liquid extraction of uranium(VI) from aqueous nitric acid with n-octyldecylsulfoxide (ODSO) in toluene has been studied over a wide range of conditions. The extracted species appears to be UO₂(NO₃)₂·2ODSO. The extraction increased with increasing nitric acid concentration up to 2.0 mol/l and then decreased. Extraction also increased with increasing extractant concentration. The influence of temperature, salting-out agent concentration and complex anion concentration on the extraction equilibrium were also investigated, and the enthalpy of the extraction reaction was calculated.     

Extraction of uranium(VI) from nitric acid solution with hexyloctylsulfoxide (HxOSO)

The thermodynamic extraction of uranium(VI) with hexyloctylsulfoxide (HxOSO) has been studied. It was found that the distribution ratio increases with increasing nitric acid concentration up to 2.3 mol/l and then decreases. The distribution ratio also increases with increasing extractant concentration. The extracted species appears to be UO₂(NO₃)₂ ^.2HxOSO. The influences of temperature, sodium nitrate and oxalate concentrations on the extraction were also investigated, and the thermodynamic functions of the extraction reaction were obtained.