T. Sekine

Solvent extraction of metal ions with mixed ligands—I: Adduct formation of Cu(II) and Zn(II) chelate complexes of thenoyltrifluoroacetone and β-isopropyltropolone

Abstract The following equilibria have been studied by distribution measurements with radioisotopes: The formation of MA2 M2+(aq) + 2HA(org) ⇌ MA2(org) + 2H+(aq) The adduct formation between MA2 and L MA2(org) + nL(org) ⇌ MA2Ln(org) where M  Cu or Zn HA = thenoyltrifluoroacetone (TTA) or β-isopropyltropolone (IPT) L = tributyl phosphate (TBP), methyl isobutyl ketone (hexone) or undissociated IPT (HA) org = hexone, chloroform or carbon tetrachloride aq = 0·1 M (H, Na)ClO4 The experimental results are shown in Figs. 1–12. Stability constants have been determined for the different systems and are summarized in Table 1. The experiments show the presence of both MA2 complexes and MA2L complexes. Some indications of ZnA2L2 are found. The relative strengths of complexes (values of the stability constants) show that the TTA complexes form more stable adducts than the IPT complexes, and that CuA2 has a smaller tendency to form an adduct than ZnA2. TBP forms more stable adducts than hexone.

Solvent extraction of metal ions with mixed ligands—V: Adduct formation of some tris-TTA complexes☆

Abstract The adduct formation of the tris-TTA complexes of In 3+ , Sc 3+ , La 3+ , Lu 3+ and Am 3+ ions have been studied by liquid-liquid distribution. The following equilibrium constants for the distribution and adduct formation have been determined at 25°C: M 3+ (aq) + 3HA (org) ⇌ MA 3 (org) + 3H + (aq); K ex MA 3 (org) + n L (org) ⇌ MA 3 L n (org) ; β n where the chelating acid, HA, is 2-thenoyltrifluoroacetone (TTA), and the neutral ligands, L, are tributylphosphate (TBP), dibutylsulfoxide (DBSO) and methylisobutylketone (hexone). The organic solvent was carbon tetrachloride and the aqueous phase was 1 M (H, Na)ClO 4 . The values of K ex and β x are given in Tables 1 and 2. InA 3 does not form adducts. ScA 3 adds one TBP but no hexone, LaA 3 , EuA 3 , LuA 3 and AmA 3 add two molecules of TBP forming adducts which are more stable than the ScA 3 adduct. The formation constants of the MA 3 (TBP) 2 adducts showed an order of stability LaA 3 > EuA 3 ≅ LuA 3 . DBSO gives similar results to TBP, but the adducts with hexone are less stable than those with TBP.

Solvent extraction of metal ions with mixed ligands—III: Adduct formation of Eu(III) and Th(IV) chelates with TTA and IPT

Abstract Adduct formation by Eu(III) and Th(IV) chelate complexes of 2-thenoyltrifluoroacetone (TTA) and β-isopropyltropolone (IPT) with tributylphosphate (TBP) and methylisobutylketone (hexone) has been studied by the distribution method using chloroform and carbon tetrachloride as organic solvent. The distribution curves showed that aqueous chelate complexes were formed in most cases. In the extraction of Eu(III) with TTA and IPT the formation of an adduct with the undissociated chelating acid was observed at high ligand concentrations M 3 + (aq) + 4 Ha (org) ⇌ MA 3 HA (org) + 3 H + (aq) where HA denotes chelating acid. In most cases an increase in the metal extraction was observed when TBP or hexone was added to the organic solvent and this effect, which is especially large for the TTA chelates, could be explained by the formation of adducts. MA N (org) + n L (org) ⇌ MA N L n (org) where L denotes the neutral, adduct-forming ligand. The overall adduct formation constants, βn = [MANLn]org[MAN]org−1[L]org−1 were determined graphically, The formation consultants were larger for the Eu(III) chelates than for the Th(IV) chelates and larger for TBP than hexone; they were also larger in CCl4 than in CHCl3.

SOLVENT EXTRACTION OF METAL IONS WITH MIXED LIGANDS. IV. EXTRACTION OF Eu(III) WITH CHELATING ACIDS AND NEUTRAL ADDUCT-FORMING LIGANDS.

Abstract The distribution of Eu(III) has been studied with various mixtures of ligands. The following results have been obtained. 1. (a) The addition of 0·1 M tributylphosphate (TBP) shifted the distribution ratio of Eu(III) between chloroform with various chelating acids and 0·1 M (H, Na)ClO 4 . The shifts (given as log DD 0 −1 ) for the different chelating acids were: 2-thenoyltrifluoroacetone (+ 3·4), 1-naphtholic acid (+1·1), β-isopropyltropolone (+0·5), 5,7-dichloro-oxine (+0·4), N-benzoylphenylhydroxylamine (no shift), dioctylphosphate (−0·3) and N-2,4-dichlorobenzoylphenylhydroxylamine (−0·4). 2. (b) The extraction of the europium(III)-TTA chelate into chloroform and carbon tetrachloride was increased by the addition of the following ligands: trioctylphosphine oxide > tributylphosphate > quinoline > coumarin > hexone > α-napthol. The adduct formation constants for EuA 3 L and in some cases EuA 3 L 2 were obtained graphically and are summarized in Table 2. The formation constants are larger in carbon tetrachloride than in chloroform. 3. (c) An increase in the distribution of Eu(III) was also observed by the addition of other chelating acids to 0·1 M TTA in chloroform (Fig. 3).

Studies on the hydrolysis of metal ions—XLIV: Extraction study of the hydrolysis of vanadium (V) at very low concentration in acid perchlorate media

The distribution of carrier-free 48V between methyl isobutyl carbinol (hexol) and 0·5 M (H,NaClO4) has been measured radiometrically at 25°C as a function of −log [H+]. Both curvefitting and letagrop adjustment with a high-speed computer were used to evaluate constants for the following equilibria: VO2++H2O⇌HVO3+H+; logK1=−3·20±0·09 HVO3⇌VO3−+H+; logK2=−3·78±0·09 HVO3(aq)⇌HVO3(hexol); logλ=1·99±0·09

Separation of europiumIII and americiumIII by solvent extraction of their metal chelate complexes

Abstract Separation of Eu 3+ and Am 3+ by solvent extraction has been studied. The distribution of chelate complexes of these metal ions between 0.1 M sodium perchlorate and chloroform or methylisobutylketone with nineteen chelating acids has been determined. Among these acids it was observed that some extract Eu 3+ into the organic phase better than Am 3+ , some extract Am 3+ better, and some extract them equally well. The separation factor, SF = D Eu / D Am , was determined for twelve of these acids by the extraction of Eu 3+ and Am 3+ from 0.1 M (H,Na)ClO 4 . The values of log SF are as follows: dibutylphosphate (DBF), + 1.36; dioctylphosphate (DOP), +1.15; 1-phenyl-3-methyl-4-acetylpyrazolone-5, + 0.54; 2-thenoyltrifluoracetone(TTA), +0.48; neocupferron,+0.24; N -benzoylphenylhydroxylamine, +0.22; N -2,4-dichlorobenzoylphenylhydroxylamine, + 0.12; β-isopropyltropolone (IPT), −0.01; 1-hydroxy-2-naphthoic acid, +0.03; 2-hydroxy-1-naphthoic acid, + 0.01; 3-hydroxy-2-naphthoic acid; −0.02; 5,7-dichloroxine, −0.99. From these results it follows that dialkylhydrogenphosphates and 5,7-dichloroxine are the most suitable chelating acids for the separation of Eu 3+ and Am 3+ by solvent extraction.

Solvent extraction of metal ions with mixed ligands—II: Mixed chelates of Cu(II) and Zn(II)

Abstract The formation of mixed chelate complexes was studied by distribution measurements in solvent extraction systems which contained both 2-thenoyltrifluoroacetone (TTA) and β-isopropyltropolone (IPT) as the chelating ligands. The extraction constants of the following reaction were determined for Cu(II) and Zn(II): M 2+ (aq) + HA(org) + HB(org) = MAB(org) + 2H + (aq) K 1 exp = [MAB] org [H + ] 2 [M 2+ ] −1 [HA] org −1 [HB] org −1 The statistical value of K 1stat was estimated from K 2 and K 0 : K 2 = [MA 2 ] org [H + ] 2 [M 2+ ] −1 [HA] org −2 K 0 = [MB 2 ] org [H + ] 2 [M 2+ ] −1 [HB] org −2 as K 1stat = 2√ ( K 2 K 0 ) The ratios K 1exp / K 1stat were calculated as in CCl 4 in CHCl 3 in hexone Cu(II) 3·6 2·7 1·5 Zn(II) ∼3 1·6 0·7 Thus, except for ZnAB in hexone, mixed complexes are more stable than statistically calculated. The stabilization decreases with the polarity of the solvent in the order CCl 4 > CHCl 3 > hexone.

Solvent extraction of metal ions with mixed ligands—VI: Extraction of In(III) and Eu(III) with mixtures of thenoyltrifluoroacetone (TTA) and β-isopropyltropolone (IPT)

Abstract Solvent extraction of In(III) and Eu(III) has been studied at 25°C in perchlorate media with mixtures of thenoyltrifluoroacetone (TTA = HA) and β-isopropyltropolone (IPT = HB) in chloroform. The distribution of In(III) into chloroform was explained by the extraction of InAaB3−a (0 ≤ a ≤ 3) BbHa+b−3 (type B), but the addition of 1M tributylphosphate (TBP = L) changes the species to EuAaB3−aL2 complexes (type C). The following equilibrium constants were calculated for types A and C: K a,3−a = [MA a B −3a ] org [H + ] 3 /[M 3+ ][HA] org a [HB] org 3−a and it was concluded that the stabilities of the mixed complexes, MA2B and MAB2, are almost the same as those statistically calculated (Table 1). Constants were calculated for the equilibria of type B only when [HA]org was kept at 0·1 M where the main species were considered to be adducts between EuA3 and HB. β n = [EuA 3 B n H n ] org/[EuA 3 ] org [HB] org n These constants seem to indicate that IPT in the undissociated form, HB, is a rather strong donor to the EuA3 chelate.

The solvent extraction of alkali metal tetraphenylborates

Abstract The extraction of sodium and small amounts of potassium, rubidium and cesium from aqueous solutions containing sodium tetraphenylborate (TPB), sodium perchlorate and perchloric acid has been studied for nitromethane, nitroethane, nitrobenzene, methyl isobutyl ketone and tributyl phosphate. Nitromethane gives the highest distribution ratio (org/aq) for the perchlorates, and nitrobenzene gives the highest distribution ratio and separation factor for the tetraphenylborates. Most distribution data could be explained by assuming that the tetraphenylborates were fully dissociated in both phases. The equilibrium constants and distribution ratios increase in the order sodium