P.K. Khopkar

Synergistic extraction of some trivalent actinides and lanthanides by thenoyltrifluoroacetone and aliquat chloride

Abstract Extraction of some trivalent actinides and lanthanides from chloride solutions by mixtures of thenoyl trifluoroacetone and Aliquat-336-S has been investigated. High synergistic effects are obtained in these extraction systems wherein the extracted species is the mixed complex [M(TTA)3·Cl]− A+, A+ being the cation of the quaternary amine. Equilibrium constants (β) for the organic phase synergistic reactions have been calculated. These are found in general to decrease with increasing Z of the trivalent lanthanides. β values for Eu(III) and Yb(III) are abnormally low, the reasons for which have been discussed.

Thiocyanate complexing of some trivalent actinides and lanthanides

Abstract Stability constants of thiocyanate complexes of La(III), Eu(III), Tb(III), Lu(III), Pu(III), Am(III) and Cm(III) have been determined in an ammonium ion medium at 30 ± 0·1°C and unit ionic strength by a solvent extraction method. The extraction data indicate the presence of only the first two thiocyanate complexes in solution in all cases. The second thiocyanate complexes of trivalent actinides are found to have a higher stability as compared to that of the second lanthanide thiocyanate complexes. Enthalpy and entropy values of Eu(III), Am(III) and Pu(III) thiocyanate complexes have been determined by the temperature variation method and indicate some inner-complex character for the trivalent actinide complexes possibly involving partial covalent bonding. The order of stabilities of the first thiocyanate complexes of the trivalent actinides Pu(III) > Am(III) ∼ Cm(III) is confirmed by an extraction chromatographic study. A similar order is suggested for higher thiocyanate complexes of the trivalent actinides from their extraction behaviour with a quaternary ammonium thiocyanate. Probable reasons for the observed order of stabilities for the actinide complexes are discussed.

EFFECT OF IONIC MEDIA ON THE STABILITY CONSTANTS OF CHLORIDE, NITRATE, AND THIOCYANATE COMPLEXES OF AMERICIUM(III) AND EUROPIUM(III).

Stability constants of Am(II) and Eu(III) complexes with chloride, nitrate and thiocyanate ions have been determined in lithium, hydrogen, sodium and ammonium ion media at 30±0·1°C and unit ionic strength, by a solvent extraction method. For chloride complexes, the first stability constant K1 has been found to increase regularly with decreasing hydration of the medium cations. The effect of medium cations on the stabilities of nitrate and thiocyanate complexes has been found to be much smaller.

Extraction of plutonium(IV), uranium(VI) and some fission products by di-n-hexyl sulphoxide

The extraction of nitric acid, plutonium, uranium and fission products such as zirconium, ruthenium and europium has been investigated using di-n-hexyl sulphoxide in Solvesso-100. Results indicate that Pu(IV), U(VI), Zr(IV) and Ru NO(III) are extracted as disolvates, whereas Eu(III) is extracted as the trisolvate. The absorption spectra of the plutonium(IV) and uranium(VI) complexes extracted are similar to those of the species extracted by TBP which indicate the similarity of the species involved. Preliminary studies show that irradiated di-n-hexyl sulphoxide extracts zirconium to a smaller extent than irradiated TBP suggesting the use of long chain aliphatic sulphoxides as promising extractants for the recovery of plutonium in high radiation fields.

Extraction of some trivalent lanthanides and americium(III) by neutral organophosphorous extractants from thiocyanate solutions

Abstract Extraction of La(III), Eu(III), Lu(III) and Am(III) from 1M NH4SCN at pH ∼ 2·8 by tri-n-octyl-phosphine oxide (TOPO), tri-n-butyl phosphine oxide (TBPO), and tri-n-butyl phosphate (TBP) in xylene medium has been studied. In this connection extraction of thiocyanic acid from 1M NH4SCN in the pH range of ∼ 2 to ∼ 3 by the three extractants in xylene has also been investigated. It has been found that thiocyanic acid is extracted as HSCN . R3PO by the three extractants and equilibrium constants for this extraction have been calculated. The metal ions are extracted as neutral, solvated, probably anhydrous species M(SCN)3.XR3PO, X in general having the values of 4 and 3 for the lighter and the heavier lanthanides respectively. The complexes Nd(SCN)3. 4TOPO and Er(SCN)3. 3TOPO have been prepared and their absorption spectra has been recorded.

Thermodynamics of synergistic extraction of europium(III) by mixtures of thenoyltrifluoroacetone and some neutral oxo-donors

Abstract The synergistic extraction of europium(III) with thenoyltrifluoroacetone (HTTA) and some neutral oxo-donors, viz. diphenyl sulphonide (DPSO), tributylphosphate (TBP) and trioctylphosphine oxide (TOPO) has been studied in benzene. Results indicate that two synergistic species having one and two oxo-donor molecules are simultaneously extracted. The thermodynamic parameters associated with the formation of these two synergistic adducts have been evaluated by the temperature coefficient method which indicate that the reactions are predominantly enthalpy stabilised. Difference in the thermodynamic behaviour of Eu(TTA) 3 ·2TOPO from that of similar adducts with TBP and DPSO has been attributed to possible steric hindrance effects of TOPO.

Synergistic Extraction of Trivalent Actinides by Mixtures of 1-Phenyl-3-methyl-4-benzoyl-pyrazolone-5 and Neutral Oxo Donors

Abstract The synergistic extraction of trivalent actinides Am, Cm, Bk, and Cf with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) and TBP or TOPO has been investigated in xylene at 30°C. With HPMBP alone, all four trivalent actinides form M(PMBP)3· HPMBP-type self-adducts. Bk(III) shows an abnormally high extraction with HPMBP alone. With TBP or TOPO(S) as neutral donor, except in the Bk/HPMBP/TBP system where Bk(PMBP)3· HPMBP·TBP was extracted, all metal ions were extracted as M(PMBP)3·S and M(PMBP)3·(S)2 into the organic phase. The equilibrium constants (β1, β2, and K 2 for the organic phase synergistic reactions have been calculated. The β1, β2 values for Bk(III)/HPMBP/TOPO system are much lower as compared to the corresponding values for other trivalent actinides. The reasons for this extraordinary behavior of Bk(III) have been discussed. The extraction behavior of the M(III)/HPMBP/S and the M(III)/HTTA/S systems has also been compared.

Complexing of californium(III) and other trivalent actinides by inorganic ligands

Stability constants of the complexes of Cf(III) with Cl−, NO3−, SCN− and SO42−: Cm(III) with Cl−, NO3− and SO42− and Am(III) with SO42− have been determined at 30°C in ammonium ion media of unit ionic strength by a solvent extraction method. Except in the Am(III)SO42− system where only the first complex exists all the other systems indicate the presence of the first two complexes. The higher stability of Cf(SCN)2+ in comparison with that of Am(SCN)2+ and Cm(SCN)2+ has been attributed to increased availability of 5ƒ orbitals for bond formation. The relative importance of inner and outer-sphere character in the complexes of trivalent actinides with inorganic ligands used has been discussed. Extraction of trivalent actinides and lanthanides by the quaternary amine Aliquat-336 from chloride, thiocyanate, nitrate and sulphate media was investigated and indicate increased stability after Cm(III)in anionic chloride, thiocyanate and nitrate complexes of trivalent actinides.

Synergistic extraction of trivalent actinides by mixtures of thenoyltrifluoroacetone and neutral oxo donors

Abstract The synergistic extraction of trivalent actinides Am, Cm, Bk, and Cf has been studied by mixtures of HTTA and TOPO as well as DOSO in xylene at 30°C. HTTA-S (TOPO, DOSO) interaction corrections have been applied to calculate the “free” S concentrations in the organic phase. In the extraction of trivalent actinides, the third-power dependence on [HTTA]org at a fixed [S]org has been observed only after applying this correction. The synergistic species M(TTA)3.S and M(TTA)3.2S were found to be extracted into the organic phase whose stability constants (β1, β2, and K 2) have been evaluated. Extraction by HTTA + S(S = TOPO, DOSO, TBP, TBTP) shows the order of extraction to be Tm > Cf > Bk > Eu > Pm > Am > Cm for the trivalent ions. The Am/Cm separation factor with the synergistic mixtures is ∼3 whereas with HTTA alone it is ∼6 when they are extracted from the chloroacetate buffer.

EXTRACTION OF AMERICIUM(III) AND EUROPIUM (III) BY DINONYLNAPTHALENE SULPHONIC ACID AND ITS SALTS.

Abstract Equilibrium constants for the exchange of monovalent cations with hydrogen ions in HDNNS dissolved in n -hexane and chloroform have been determined at an ionic strength of unity. Extraction of Am(III) and Eu(III) from various acids and salt solutions containing the monovalent cations has been studied with reference to the selectivity of DNNS − for these ions.