Synergistic Solvent Extraction Research Articles

The thermodynamics of synergistic solvent extraction of zinc(II)

The thermodynamics of the synergistic solvent extraction of zinc(II) by HTTA-TBP mixtures were studied using radiochemical techniques. The thermodynamic values of the extraction equations indicate that the mechanism of adduct formation by TBP with the Zn(TTA) 2 chelate involves expansion of the coordination number of the central metal ion from 4 to 5. The extraction of zinc(II) by HDEHP-TBP mixtures was also studied but no synergistic effect was seen in this extraction system.

Thio-β-diketonates of lanthanides—III synergistic solvent extraction behavior of neodymium(III) with 1,1,1-trifluoro-4(2-thienyl)-4-mercaptobut-3-en-2-one (HSTTA) and some neutral donors

The synergistic solvent extraction behavior of Nd(III) with HSTTA and the neutral donors dipyridyl, tributylphosphate (TBP) and tri- n-octylphosphine oxide (TOPO) (≡L) have been investigated using benzene as the organic solvent and an ionic strength 0.1 (NaClO 4). The extraction process is governed by the following reaction equilibrium Nd 3+ 3HSTTA (O)+n L (O)⇆ Nd(STTA) 3 (L) n(O)+ 3H + The extraction constants ( K 3,n ∗ ) and the adduct formation constants ( β 3, n ) have been evaluated. With dipyridyl, only mono adduct formation takes place, whereas, with TBP and TOPO, both mono and bis adducts are formed. The β 3, n values for HSTTA systems are higher than for the corresponding HTTA systems.

Synergic extraction of zinc, cadmium and lead with hexafluoroacetylacetone and di-n-butylsulphoxide and tri-n-butyl phosphate, and the gas chromatography of the zinc adduct

The synergic solvent extraction of zinc(II), cadmium(II), and lead(II) with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione, H(HFA), and tri-n-butyl phosphate (TBP) or di-n-butylsulphoxide (DBSO) as neutral donors, into cyclohexane has been investigated. Quantitative extraction occurs at pH 4.5–6.0 in extraction times of 10–30 min, depending on the metal species. The optimum pH, equilibration time, stoichiometry and stability of the extracted species, as well as the effect of fluorinated β-diketone concentration, metal concentration and neutral donor concentration on the extraction are reported. The extracted species was found to be M(HFA) 2.2DBSO or M(HFA) 2.2TBP by mass-action studies. Thermogravimetric analysis of the complexes is reported. The gas chromatographic behaviour of the ternary complexes of the three metals has also been studied. A calibration plot of peak area vs. the amount of zinc injected was linear over the range 40–900 ng of zinc for the Zn(HFA) 2. 2DBSO species; the cadmium and lead species apparently decomposed on the column and useful chromatographic peaks were not observed. The calibration plot for zinc was determined on the basis of the averages of 3–5 replicate determinations for 14 different concentrations over the range stated. The average relative standard deviation was 2.9%.

Synergistic solvent extraction of adducts formed by Di- n-butyl sulphoxide and rare-earth tris-thenoyltrifluoroacetonates

Extraction equilibrium constants, K 3,n ∗ , and organic phase adduct formation constants, β 3, n , have been determined by liquid-liquid distribution of radioactive rare-earth tracers between 1 M (H, Na)ClO 4 and CCl 4 with 0·2 M HTTA and ⪯0·2 M DBSO at (23±2)°C. A comparative study on the synergistic extraction with DBSO and TBP as neutral ligands is reported. Tetravalency of Ce and Tb is discussed in connection with their extraction properties.

Temperature effects in synergistic solvent extraction

Abstract The extraction of Eu(III) and Tm(III) has been studied in mixed systems of TTA + TBP and TTA + AA (TTA = 2-thenoyltrifluoroacetone; TBP = tributylphosphate; AA = acetylacetone). The formation constants of Eu(TTA) 3 , Eu(TTA) 3 (TBP) 2 , Eu(TTA) 3 ( AA), Tm(TTA) 3 , Tm(TTA) 3 (TBP) and Tm(TTA) 3 (AA) were measured as a function of temperature to obtain free energy, enthalpy and entropy changes. The thermodynamic parameters support a mechanism for synergism in which the coordination number of the lanthanide ion expands when Ln(TTA) 3 forms Ln(TTA) 3 (( S ) n where S is TBP or AA.

Synergistic solvent extraction of rare-earth metal ions with thenoyltrifluoroacetone admixed with tributylphosphate

Extraction equilibrium constants have been determined for the formation of mixed complexes of thenoyltrifluoroacetone (HTTA) and tri- n-butyl phosphate (TBP) with all the rare earths except La and Eu, but including Y. The organic diluent was carbon tetrachloride containing 0·2 M HTTA initially and the aqueous phase was kept at constant ionic strength with 1 M (H,Na)ClO 4. Equilibrations of the phases were performed at (23 ± 2)°C. The logarithms of the extraction constants, log K 3,1 ∗ and log K 3,2 ∗ , together with the calculated logarithms of the formation constants of complexes between tris-TTA chelates and TBP in the organic phase, log β 3,1 and β 3,2, are summarized. The variation of log K 3,n ∗ and log β 3, n with atomic numbers, Z, shows interesting tetrad effects.

Synergistic solvent extraction of some “4ƒ” elements from molten alkali nitrates at 160°C

Synergistic extraction of some rare earths elements Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Tm and Yb in (LiK)NO 3 eutectic at 160°C has been studied with the following mixtures: system I, Thenoyltrifluoroacetone (HTTA) + ethylene bis (diphenylphosphine oxide)(2DPO) and system II, hexamethylphosphorotriamide (HMPT) + (2-DPO). These different reagents were diluted in a eutectic of polyphenyls. At the maximum of the synergistic effect, the mixed extracted species are respectively Ln(TTA) 3(2-DPO) and Ln(NO 3) 3(HMPT)(2-DPO) for all the lanthanides. With these two systems, the synergistic effect is small. But with the system I, an enrichment of the organic phase in the heaver lanthanide is possible.

Synergic solvent extraction of divalent cations with decafluoroheptanedione and di-n-butylsulfoxide

The synergic solvent extraction of iron(II), cobalt(II), nickel(II) and lead(II) with l,l,l,2,2,6,6,7,7,7-decafluoro-3,5-heptanedione(H(FHD)) and di-n-butylsulfoxide (DBSO), is described. The divalent cations are extracted with 99.9% efficiency at pH 5.5 in extraction times of less than 15 min. The extracted species was shown to be M(FHD) 2·2 DBSO by mass action studies and elemental analyses. The extraction of copper(II) was also studied. No DBSO adduct was found in the copper extraction.

Further studies of the rate affected synergic solvent extraction of Fe(III)-TTA—II: The effect of tributyl phosphate on the solvent extraction of iron(II) with 2-thenoyltrifluoroacetone

The extraction of iron(III) from aqueous perchloroc acid into a solution of 2-thenoyltrifluoroacetone (TTA) in benzene is known to be very slow. The system does not reach equilibrium within a practical contact time of the two phases. The rate and percent of iron(III) extraction was found to increase considerably upon the addition of tributyl phosphate (TBP). An increase in temperature of 10°C results in further increase in the rate and percent of iron(III) extraction by a factor of 1·5. From the results of detailed investigation, the reason for this effect is considered to be the replacement of a slow step (the direct formation of the iron(III)-TTA complex in the aqueous phase) by a series of fast reactions (the formation of an iron(III) TBP complex in the aqueous phase, the extraction of the iron-(III)-TBP complex to the organic phase, and the replacement of TBP by TTA in the organic phase). All the observations in this system are readily explained by the previously demonstrated kinetic effect.

Further studies of the rate affected synergic solvent extraction of Fe(III)-TTA—I: The effect of tri- n-octylphosphine oxide on the solvent extraction of iron(III) with 2-thenoyltrifluoroacetone

The extraction of iron from aqueous perchloric acid into a solution of TTA in benzene is known to be very slow. The system does not reach equilibrium within a practical contact time of the two phases. The addition of tri- n-octylphosphine oxide (TOPO) and a mixture of tri- n-octylphosphine oxide with chloride ion was found to increase the rate considerably. From the results of detailed investigation, the reason for this effect is considered to be the replacement of a slow step, the direct formation of the Fe(TTA) 3 in the aqueous phase, by a series of fast reactions — the formation of an iron-tri- n-octylphosphine oxide species in the aqueous phase, followed by its extraction into the organic phase and its reaction with TTA in the organic phase.

Synergic solvent extraction of lanthanides with mixtures of aliphatic fluorinated β-diketones and organophosphorus donors

The extraction of lanthanides from an aqueous acetatechloride medium into cyclohexane solutions of trifluoroacetylacetone, hexafluoroacetylacctone, 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione and tri-n-butyl phosphate was studied. The extraction properties of other fluorinated aliphatic β-diketones and fluoroorganophosphates were also investigated. The efficiency of the extraction of the lanthanides, the composition of the complexes transferred to the organic phase and the extraction and stability constants for the synergic reactions were determined. Synergic extraction, as a technique for the preparation of lanthanide species, was evaluated for compatibility with subsequent gas chromatography. The lanthanides were found to be rapidly and quantitatively transferred into organic phases containing mixtures of fluorinated aliphatic β-diketones and TBP. The resulting mixed complexes that contained fully fluorinated β-diketones had a distinct stoichiometry and were thermodynamically more stable dan similar mixed complexes of partially fluorinated β-diketones. These properties of the synergic systems allow precise control of the formation of anhydrous complexes in the organic phase and are compatible with the use of these systems for gas chromatography.

Acetylacetone adducts of rare earth tris-thenoyltrifluoroacetonates in synergistic solvent extraction

The synergistic effect of acetylacetone (Hacac) in the extraction of rare earth thenoyltrifluoroacetonates (Mtta 3) was attributed to the formation of the species Mtta 3 · Hacac. The adduct was isolated and identified by chemical analyses and i.r. spectra.

The Synergic Solvent Extraction of Rare Earths. II. The Absorption Spectra of Neodymium-, Holmium-, and Erbium-TTA-TOPO Complexes with ClO4−, CNS− , NO3−, and Cl− Ions

Abstract The synergic solvent extraction behavior of neodymium, holmium, and erbium in Ln3+/X−/HTTA/TOPO systems (X−=ClO4−, CNS−, NO3−, and Cl−) have been investigated. When the rare earths are completely extracted into an organic layer, the following equation is assumed: Ln(TTA)3(TOPO)2(0)+3TOPO(0)+H(a)++X(a)−\ightleftharpoons(Ln(TTA)2(TOPO)5)+X(0)−+HTTA(0) for which the mixed equilibrium constant is defined by k3=[(Ln(TTA)2(TOPO)5)+X−](0) [HTTA](0)/[Ln(TTA)3-(TOPO)2](0)[TOPO]3(0) [H+](a)[X−](a). The logk3 value for the holmium/ClO4−, /CNS−, /NO3−, and /Cl− systems are about 8.3, 6.5, 5.3, and 3.6 respectively. An obvious difference between Ln3+/SO42−/HTTA/TOPO and Ln3+/ClO4−/HTTA/TOPO systems is observed in the order of the distribution ratio on the extraction of a series of rare earths with an increase in the atomic number.

Synergistic solvent extraction of rare earths by mixtures of thenoyltrifluoroacetone and acetylacetone

The synergistic extraction of the thenoyltrifluoroacetonates of neodymium, samarium, gadolinium, dysprosium, and erbium by acetylacetone was studied using mixtures of the two β-diketones. The synergistic shift of the extraction curves decreases the separability of the rare earth chelates.

Synergic solvent extraction of rare earths—I Spectrophotometric investigation of holmium-and erbium-TTA-TOPO complexes with perchlorate ion

Synergic solvent extraction behavior of holmium and erbium in Ln 3+/ClO 4 −/HTTA/TOPO system have been investigated spectrophotometrically. The formulae of these complexes with perchlorate ion were estimated to be (Ln(TTA) 2(TOPO) 5) +ClO 4 − which gave a strong band with a maximum of 445 mμ for holmium and 518 mμ for erbium, respectively, and showed a considerable electric conductivity in a polar organic solvent. When the rare earth is completely extracted into an organic layer, the following equation is assumed. Ln( TTA) 3( TOPO) 2(0)+3 TOPO (0)+H + (a)+ CIO − 4(a)⇌ ( Ln( TTA) 2( TOPO) 5)+ CIO − 4(0)+ HTTA (0) for which the mixed equilibrium constant is defined by κ 3 = [(Ln(TTA) 2(TOPO) 5) +ClO 4 +] (0) −[HTTA] (0)/[Ln(TTA) 3(TOPO) The log κ 3 increases linearly with increase in the dielectric constant of the organic solvent used. The discrepancy in the distribution coefficient of rare earths between ClO 4 −/HTTA/TOPO and Cl −/HTTA/TOPO systems also increases with increase in the dielectric constant.

Synergic solvent extraction of europium(III) into mixtures of 2-thenoyltrifluoroacetone with various alkylphosphine oxides

The synergic solvent extraction of tracer europium(III) from chloride medium into mixtures of thenoyltrifluoroacetone (HTTA) with methylenebis(di-n-hexylphosphine oxide), MHDPO; trimethylenebis(di-n-hexylphosphine oxide), PHDPO; tetramethylenebis(di-n-hexylphosphine oxide), BHDPO; or tri-n-octylphosphine oxide, TOPO, in cyclohexane was studied. The europium-containing species in the organic phase were shown to be Eu(TTA) 3(TOPO) 2, Eu(TTA) 3(TOPO) 2, Eu(TTA) 3(MHDPO), Eu(TTA) 3(PHDPO), and Eu(TTA) 3(BHDPO). A solvent extraction-molar ration study using an acetate aqueous medium confirmed these stoichiometries and showed the formation of Eu(TTA) 3(TOPO). The formation of Eu(TTA) 3(TOPO) was confirmed with a loading capacity study. The synergic solvent extraction of tracer europium(III) from perchlorate medium into mixtures of HTTA and TOPO or HTTA and MHDPO in cyclohexane was also studied. The europium-containing species in the organic phase were shown to be Eu(TTA) 3(TOPO) 2 and Eu(TTA)-(ClO 4) 2(MHDPO) 3. Equilibrium constants for the formation of all of the above complexes were calculated.

Spectrophotometric Investigation and Analytical Application of the Synergic Solvent Extraction of Rare Earths with Mixtures of 2-Thenoyltrifluoroacetone and Tri-n-octyl Phosphine Oxide.

Spectrophotometric Investigation and Analytical Application of the Synergic Solvent Extraction of Rare Earths with Mixtures of 2-Thenoyltrifluoroacetone and Tri-<i>n</i>-octyl Phosphine Oxide.

Use of the Synergic Solvent Extraction System for the Determination of the Stability Constants of Metal Complexes

Use of the Synergic Solvent Extraction System for the Determination of the Stability Constants of Metal Complexes

A spectrophotometric investigation of the synergic solvent extraction system uranyl ion/tri-(n-octyl) phosphine oxide (TOPO)/di(2-ethylhexyl) phosphoric acid (D2EHPA)

A spectrophotometric investigation of the synergic solvent extraction system uranyl ion/tri-(n-octyl) phosphine oxide (TOPO)/di(2-ethylhexyl) phosphoric acid (D2EHPA)