Metal Extraction by Sulfur‐Containing Symmetrically‐Substituted Bisphosphonic Acids. Part I. P,P′‐di(2‐ethylhexyl) Methylenebisthio‐Phosphonic Acid

Abstract

P,P′‐dialkyl methylenebisphosphonic acids are powerful metal extraction reagents exhibiting strong affinity for a variety of metal ions, especially lanthanides and actinides. While the affinity of gem‐bisphosphonic acids is generally high for most metal ions because of their relative high acidity and ability to form six‐member chelate rings, the selectivity often is low. Thus, a strategy of incorporating soft‐donor atoms such as sulfur into gem‐bisphosphonic acids has been adopted to obtain enhanced metal selectivity while retaining high extraction efficiency. To this end a new class of sulfur‐containing gem‐bisphosphonic acid solvent extraction reagents was designed, synthesized, and evaluated for heavy element separations. Specifically, the novel sulfur‐containing P,P′‐di(2‐ethylhexyl) methylenebisthiophosphonic acid, H₂DEH[MBTP], was synthesized, characterized and its aggregation, metal extraction and acid‐base behavior assessed. Vapor phase osmometry measurements indicate that H₂DEH[MBTP] is less aggregated than its P,P′‐di(2‐ethylhexyl) methylenebisphosphonic acid analogue, H₂DEH[MBP], existing in toluene primarily as an equilibrium mixture of monomer and dimer in the concentration range studied. The acid dependency data for the extraction of Am³⁺ and Eu³⁺ from aqueous perchlorate solutions by H₂DEH[MBTP] in o‐xylene exhibit slopes close to ?3 at low acidity, consistent with extraction of a trivalent metal ion. The extractant dependency data exhibit pH dependent slopes, suggesting different stoichiometry of metal extraction under different acidities.     

Extraction of lanthanides(III) from Perchlorate Solutions with Carbamoyl- and Phosphorylmethoxymethylphosphine Oxides and Tetrabutyldiglycolamide

The solvent extraction of Ln(III) ions from perchlorate aqueous solutions into an organic phase containing neutral polyfunctional organophosphorus ligands R₂P(O)CH₂OCH₂C(O)NBu₂ R = Bu (I), R = Ph (II) and R₂P(O)CH₂OCH₂P(O)R¹₂ R = R¹ = Bu (III); R = Bu, R¹ = Ph (IV); R = R¹ = Ph(V) has been studied. Their extraction behavior was compared with that of tetrabutyldiglycolamide (TBDGA), tetrabutylmethylenediphosphine dioxide (VI), P,P-dibutyl-P’P’-diphenylmethylenediphosphine dioxide (VII), tetraphenylmethylenediphosphine dioxide (VIII), dibutyl-N,N-dibutylcarbamoylmethylphosphine oxide (IX) and diphenyl-N,N-dibutylcarbamoylmethylphosphine oxide (X). The extraction equilibrium was investigated, and the equilibrium constants were calculated. It was found that the lanthanide(III) ions are extracted with the studied extractants from perchlorate solutions as LnL₃(ClO₄)₃ complexes. In the NaClO₄ media, TBDGA was found to possess a higher extraction efficiency towards Ln(III) ions than other neutral donor ligands studied. A successive replacement of the C(O)NBu₂ groups in the diglycolamide extractant molecule by phosphoryl ones leads to a decrease in the extraction efficiency of Ln(III) ions. In the NaClO₄ media, compounds II, IV and V with phenyl radicals at the P(O) group demonstrate a lower extraction efficiency towards Ln(III) ions than their butyl-substituted analogs. In contrast, phenyl-substituted diphosphine dioxides VIII, VII and carbamoylmethylphosphine oxide (X) extract Ln(III) ions more effectively than their butyl-substituted analogs VI and IX. The extraction of Ln(III) ions from HClO₄ solutions is accompanied by HClO₄ interaction with neutral donor extractants, which leads to a decrease of the free extractant concentration in the organic phase. By this reason, an increase in the HClO₄ concentration higher than 0.1 M is accompanied by a decrease of the Ln(III) extraction with TBDGA. In the 3 M HClO₄ system, diphosphine dioxide VIII outperforms TBDGA at the Ln(III) extraction.     

SYNERGISTIC EFFECTS IN SOLVENT-EXTRACTION SYSTEMS BASED ON ALKYLSALICYLIC ACIDS. IV. EXTRACTION OF THE TRIVALENT RARE-EARTH METALS IN THE PRESENCE OF BIFUNCTIONAL C=0, P=0 AND S=0 COMPOUNDS

ABSTRACT

Several bifunctional compounds of different types (diamides, diphosphonates and disulphoxides) were synthesized, and their effect on the extraction of the trivalent rare-earth metals from chloride media by solutions of some alkylsalicylic acids (HA) in xylene was investigated. Appreciable synergistic shifts in the individual pH₅₀ values were observed in most cases, the shifts generally increasing in the order S=0 ≤ C=0 < P=0 for comparable bifunctional compounds containing these donor groups. For compounds with C=0 or P=0 groups, the synergism is greater when the two groups are separated by a one-carbon bridge (-CH₂-) than by a two-carbon bridge (-CH₂-CH₂-), whereas the opposite is true for compounds containing S=0 groups. For a given bifunctional compound, the synergistic shifts were found to increase with increasing steric bulk of the alkylsalicylic acid

The synergistic shifts produced by the addition of a given bifunctional compound generally decrease across the lanthanide series (La to Lu), which suggests that coordination of the neutral ligand is somewhat dependent on steric factors. For the diamides and diphosphonates containing a -CH₂- bridge, the synergistic effects in the extraction of neodymium (and lanthanum) are substantially greater than for their monofunctional analogues, which suggests that these bifunctional compounds may be coordinated to these metals in a bidentate mode. Slope analysis studies and measurements of the solubility of the neodymium-alkylsalicylic acid complex in xylene solutions of the bifunctional ligands (L) are consistent with the formation of complexes of stoichiometry NdA₃L.     

Synergistic Solvent Extraction of Lanthanides(III) with Mixtures of 4-benzoyl-3-methyl-1-phenylpyrazol-5-one and Some Novel Carbamoyl- and Phosphorylmethoxymethylphosphine Oxides

The solvent extraction of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y from weak acidic hydrochloric acid solutions into an organic phase containing 4-benzoyl-3-methyl-1-phenylpyrazol-5-one (HP) and neutral tridentate organophosphorus ligands R₂P(O)CH₂OCH₂C(O)NBu₂ R = Bu (I), R = Ph (II) and R₂P(O)CH₂OCH₂P(O)R¹₂ R = R¹ = Bu (III); R = Bu, R¹ = Ph (IV); R = R¹ = Ph(V) has been studied. A considerable synergistic effect was observed in the presence of HP in the organic phase containing tetraoctyldiglycolamide (TODGA) and neutral organophosphorus ligands I - V. A successive replacement of C(O)NAlk₂ groups in the diglycolamide extractant molecule by P(O)Ph₂ groups leads to an increase in the extraction efficiency of Ln(III) ions when toluene was used as diluent. Phosphoryl-containing podand I possess a higher extraction efficiency towards Ln(III) ions than TODGA. The extraction equilibrium was investigated and the equilibrium constants were calculated. It was found that the lanthanide(III) ions are extracted as LnLP₃ and LnL₂P₃ complexes with mixtures of HP and I in toluene from weak acidic solutions.     

METAL EXTRACTION BY ALKYL SUBSTITUTED DIPHOSPHONIC ACIDS. PART 4 P,P′-DI(2-ETHYLHEXYL) BUTANEDIPHOSPHONIC ACID

ABSTRACT

As part of an ongoing investigation of the properties of dialkyl substituted diphosphonic acids as solvent extraction reagents for metal cations, we have studied the extraction of alkaline earth cations, Fe(III) and representative actinides (Am(III), U(VI) and Th(IV)) at tracer-level concentration by o-xylene solutions of P,P′-di(2-ethylhexyl) butanediphosphonic acid, H₂DEH[BuDP]. The extractant and acid dependencies of these metal ions exhibited significant differences from those of the previously investigated analogous extractants in which the two phosphonate groups are separated by a methylene or an ethylene bridge. The aggregation of H₂DEH[BuDP] was investigated in toluene at 25° C by vapor pressure osmometry. H₂DEH[BuDP] was found to exist predominantly as a trimeric species in the 0.1-0.005 molal concentration range. Osmometric measurements and infrared spectra indicate that Ca(II) is extracted into H₂DEH[BuDP] solutions with little disruption of the structure of the extractant. Iron(III) causes significant deprotonation of the ligand and dramatically changes the apparent aggregation number. A comparison of the extraction of Ca(II), Am(III) and Fe(III) by H₂DEH[BuDP] with data obtained using bis(2-ethylhexyl) phosphoric acid (HDEHP) or 2-ethylhexyl 2-ethylhexylphosphonic acid (HEH[EHP]) as the extractant indicates that H₂DEH[BuDP] has characteristics similar to these monofunctional analogs. Infrared spectra of the Ca(II) and Fe(III) salts of H₂DEH[BuDP] show a shift of both v_asym (POO?) and v_sym (POO?) to lower frequencies relative to their values in the sodium salt. This indicates a symmetrical interaction between the metal ion and the phosphonate groups through chelate and/or bridging interactions.     

Solvent Extraction of Copper from Nitrate Media with Chelating LIX‐Reagents: Comparative Equilibrium Study

Abstract

Comparative experimental studies were carried out on extraction of copper(II) cations from aqueous acid nitrate media using four LIX‐reagents, representatives of different extractant classes: LIX 984N‐I, LIX 860N, LIX 84‐I and LIX 65N. As a diluent, liquid hydrocarbon undecane was used. The extraction behavior of the LIX‐reagents was compared based on an analysis of the influence of the main factors on the two‐phase mass transfer process: aqueous pH‐value, initial copper and extractant concentrations, and temperature. The experimental data received were used in the calculation of important parameters characterizing the efficiency of copper extraction from nitrate media with different LIX reagents: distribution ratios D, concentration extraction constants K _ex, pH_0.5‐values, and thermodynamic parameters such as enthalpy, entropy, and free energy changes (ΔH ⁰, ΔS ⁰, ΔG ⁰‐values).     

ACIDS. PART 1. P,P"-DI(2-ETHYLHEXYL) METHANEDIPHOSPHONIC ACID

ABSTRACT

Two novel extractants, P,P'-di(2-ethylhexyl) methanediphosphonic acid (H2DEH[MDP]) and P.P'-dioctyl methanediphosphonic acid (H2DO[MDP]) have been synthesized at high purity and yield. H₂DEH[MDP] was selected for metal extraction studies because of its better physical properties. An investigation of the extraction of alkaline earth cations, Fe(III) and representative tri-, tetra- and hexavalent actinide ions from nitric acid solutions into o-xylene solutions of H₂DEH[MDP] at different concentrations was performed. With a few exceptions, the acid dependencies of the extraction of the above metal species strongly resembles those measured in the uptake of the same metals by the chelating ion exchange resin Diphonix®, which contains gem-diphosphonic acid groups chemically attached to a polymeric matrix. H₂DEH[MDP] exhibits practically no selectivity among the alkaline earth cations. The almost lack of acid dependency observed with Fe(lll) and tetra- and hexavalent actinides indicates that these ions are chelated by H₂DEH[MDP] mostly through the P=0 groups of the extractant. With Fe(lll) and the actinides, variable slopes of the extractant dependencies were measured, their values being strongly dependent on the acidity of the aqueous phase. Typically, the slope of the extractant dependency has a value of about two if the metal is extracted from high acidity solutions. This value becomes progressively lower as the aqueous acidity is reduced, tending to almost zero for acidities around 0.1 M. This phenomenon has been attributed to the formation of metal complexes having different stoichiometrics, ligand protonation and solubility in the aqueous phase.

H₂DEH[MDP] possesses an extraordinary affinity for actinides and Fe(III). In analogy with the Diphonix resin, this property can be exploited for actinide preconcentration and separation from complex matrices of analytical interest and from mixed waste solutions.     

Selektivitätsstudien: OH-, NH- und SH-gruppenspezifische Reagentien – ihre Anwendung in der organischen Analytik und als Schutzgruppen in der Synthese

Selectivity: OH-, NH- and SH-Groupspecific Reagents. The Application in Organic Analysis and as Protective Groups Phosphylhalides and -pseudohalides R¹R²P(O)X (X = Cl, F, CN, N₃, OC₆H₄NO₂(p)) reactdepending on X- with a different selectivity with OHNH- and SH-groups. Vinylsulfones ArSO₂CH = CH₂ are SH-selective. Silanes R₃SiH are OH-selective. By exchange of one ligand bound on P, SO₂ or Si by the 5-dimethylamino resp. the 5-methoxynaphthalinogroup reagents are formed, which combine group selectivity with fluorescence. The fluorescence is quenched if a ligand or the leaving group is substituted by a NO₂-group. The fluorescence appears again if after the group selective fixation the ligand with the nitrogroup is split off. In serine enzymes (α-chymotrypsine, trypsin, butyryl- and acetylcholinesterase, subtilisine) and insuline (after the reductive opening of the S-S bridges) the primary OH-groups in the active site in the enzymes resp. the SH groups in the reduced insuline were substituted with fluorescing groups using group selective fluorescing reagents.     

SOLVENT EXTRACTION OF Ni(ll) WITH THE ACTIVE COMPONENT OF LIX 54

ABSTRACT

The solvent extraction of Ni(II) with the active component of the commercial extractant Lix 54 in different synergic mixtures, using tri-n-octylphosphine oxide (TOPO), tri-n-laurylamine (TLA), di-(2-ethylhexyl)phosphoric acid (HDEHP), tributylphosphate (TBP) and 4-methylpyridine as synergic reagents is compared in this work, the highest synergic effects corresponding to the presence of TOPO and 4-methylpyridine. For this reason, the extraction of Ni(ll) from a 1.0 mol.dnr³ KN0₃media by the mixture of the active component of Lix 54 and 4-methylpyridine has been extensively studied in this work. The results have been treated both graphically and numerically in order to find a suitable chemical model of the species responsible for the extraction as well as their extraction constants.     

SELECTIVE EXTRACTION OF PALLADIUM(II) FROM CHLORIDE SOLUTIONS WITH NONYLTHIOUREA DISSOLVED IN CHLOROFORM

ABSTRACT

The extraction of Palladium(II) [Pd(II)] from hydrochloric acid solutions with nonylthiourea (NTH) dissolved in chloroform at a constant ionic strength of 1.0?M has been studied. The extraction of Pd(II) has been investigated as a function of the concentration of the extractant, chloride ion, and proton concentrations as well as extraction temperature. The distribution data have been treated graphically and numerically. The analysis of the experimental data has shown that Pd(II) is extracted as PdCl₂·(NTH) and PdCl₂·(NTH)₂ species with the respective extraction constants of log?K ₁₁=5.0±0.1 and log?K ₁₂=9.1±0.1. The back-extraction of Pd(II) from the organic phase using different stripping reagents has been examined. The selectivity of NTH for Pd(II) against Pt(IV), Rh(III), Cu(II), Fe(III), and Zn(II) has also been investigated.     

TETRA-BUTYL-MALONAMIDE AND TETRA-ISOBUTYL MALONAMIDE AS EXTRACTANTS FOR URANIUM(VI) AND PLUTONIUM(IV)

ABSTRACT

Two new symmetrical diamides, namely straight-chain alkyl substituted neutral tetra-butyl-malonamide(TBMA) and sterlcally hindered branched-chain alkyl substituted tetra-isobutyl malonamide(TIBMA) were synthesised, characterised and used for the extraction of U(VI) and Pu(IV) from nitric acid media into n-dodecane. Both the cations were found to be extracted as their disolvates. Interestingly TBMA extracted more efficiently than TIBMA but afforded poor selectivity for Pu/U separation. The thermodynamic parameters involved in the extraction, determined by the temperature variation method, indicated the reactions in all cases to be enthalpy favoured. Entropy was found to be counteracting the extraction of U(VI) and favouring the extraction of Pu(IV). The recovery of diamides from the loaded actinides could be easily accomplished by using dilute oxalic acid or dilute U(IV) as the strippant for Pu(IV) and using dilute Na₂C0₃ as that for U(VI).     

Palladium Isolation and Purification from Nitrate Media: Efficient Process Based on Malonamides

ABSTRACT

Solvents based on malonamides have been described to be very efficient and selective for liquid-liquid extraction of Pd(II) from nitrate media. The present study details the possibility to selectively extract Pd(II) over common metallic cations, Cu(II), Ni(II), Co(II), Zn(II), Nd(III), Fe(III) and Al(III) using N,N’-dimethyl,N,N’-dibutyltetradecylmalonamide (DMDBTDMA) in toluene. The lowest selectivity was obtained considering Fe(III) and Nd(III), the extraction of all other cations being negligible. Pd(II) distribution and selectivity regarding Fe(III) have been fine-tuned using the aqueous HNO₃ concentration as the sole parameter, so that extraction, scrubbing and stripping steps can be simply designed without the need for other specific metal chelating reagents and/or aqueous media and without the extensive generation of aqueous effluents. DMDBTDMA was also benchmarked with other classical Pd(II) extractants such as tributylphosphate (TBP), dihexylsulfide (DHS), tetraoctyl diglycolamide (TODGA) and bis(2-ethylhexyl)sulfoxide (BESO) in toluene and in n-heptane. Overall, this study reveals that malonamides are very well positioned and should be considered for further processing of aqueous nitrate wastes containing Pd contaminated with common base metals.     

Solvent Extraction Behavior of Plutonium (IV) Ions in the Presence of Simple Hydroxamic Acids

Abstract

Formo‐ and aceto‐hydroxamic acids are very effective reagents for stripping Pu(IV) ions from a tri‐butyl phosphate phase into nitric acid. Distribution data for Pu(IV) in the presence of these hydroxamate ions have been obtained and trends established. The affinity of aceto‐hydroxamic acid for Pu(IV) ions and its selectivity over U(VI) ions is demonstrated by the values of the stability constants in HClO₄. These data support the applications of simple hydroxamic acids in advanced Purex‐type solvent extraction systems.     

NEW XANTHIC ACID DERIVATIVES AS POTENTIAL REAGENTS IN THE SOLVENT EXTRACTION OF PRECIOUS METAL IONS: EXTRACTION OF PALLADIUM(II) WITH 13-BIS(0-BUTYLXANTHATO)PROPANE

ABSTRACT

Two series of new xanthic acid derivatives namely, the bis (O-butylxanthato) alkanes ( abbreviated as BBXAs or simply as bis-xanthates in this paper) have been synthesized in connection with the solvent extraction of precious metal ions. From an aqueous medium containing 0.1 M NaC10₄ (1 M=l mol dm^-3), these compounds exhibited high selectivity for extraction of Pd(II) and Ag(I) in dichloroethane, over most of the base metals as well as Pt(IV) and Au(III) ions. Towards Pd(II) and Ag(I) ions, the bis compounds act as SS chelating agents where the stabilities of the extractable complexes are determined by the length of the alkylene chain existing between the donor atoms. Pd(II) extraction has been studied in detail taking 13-bis(O-n-butylxanthato)propane (BnBXP) as the representative member of the series of bis-xanthates synthesized in this work. The extraction of palladium(II) was found to be quite slow in pure chloride medium. But, a mixed acid medium containing H₂SO₄ or HNO₃ in the presence of smaller amount of chloride ion provided optimum reversible extraction of palladium in dichloroethane, where Pd(II) forms 1:1 extractabic complexes with BnBXP. Pd(II) extraction is described in terms of the aqueous phase compositions, extraction and back-extraction data, extraction equilibrium, selectivity considerations and probable mechanisms of extraction.     

SPECTROSCOPY OF INDIUM(III) LIPOPHILIC SPECIES EXTRACTABLE FROM PERCHLORATE MEDIUM BY TWO 1-PHENYL-3-METHYL-4-ACYL-PYRAZOL-5-OLS AND TRI-N-OCTYLPHOSPHINE OXIDE*

ABSTRACT

With the aim of improving our knowledge about the extraction of indium from perchlorate media, by 1-phenyl-3-methyl-4-acyl-pyrazol-5-ols, “HL” ( acyl = benzoyl or thenoyl) and their mixtures with tri-n-octylphosphine oxide, “TOPO”, in toluene, synthetic and extraction organic phases, and extractable conplexes, have been studied by phosphorus-31 and proton NMR, and by IR spectroscopy.

As expected from the extraction equilibria, only one species is extracted by HL. It is identified as a tris-chelate by comparison with the synthesized complexes InL₃(H₂O)_z (z = 0, 2). The synergistic mixtures HL + x TOPO extract several species InL₃(TOPO)_n ( n.≥. 0, depending upon x). A coordination number of In higher than 6 is suggested.

The only way to obtain strong In ? O = PR₃ bonds is the extraction of indium, therefore, the reaction:     

Pyridinedicarboxylic Acid Diamides as Selective Ligands for Extraction and Separation of Trivalent Lanthanides and Actinides: DFT Study

This article presents a general approach to solving the urgent practical problem of separation of 4f-(lanthanides, Ln³⁺) and 5f-elements (actinides, An³⁺) very similar in properties based on the DFT quantum-chemical supercomputer simulation of Ln³⁺ and An³⁺ complexes with polydentate nitrogen-containing heterocyclic ligands. The method allows to calculate the geometry parameters of ligands and complexes and the metal to ligand binding energies with accuracy, permitting a direct comparison of calculation results with the experimental data, and estimate selectivity factors for separation of Eu³⁺/Am³⁺ model pair cations (SF_Am/Eu) in extraction experiments on a semi-quantitative level.

The applicability of the method and the approach demonstrated by DFT-modeling (nonempirical PBE functional, extended relativistic full-electron basis set) of a large series of diamides of pyridine-2,6-dicarboxylic (dipicolinic) acid (L) with different substituents at the amide nitrogen atoms and in the pyridine cycle, as well as their complexes [LM]³⁺, (H₂O)_nM(NO₃)₃ (n = 3, 4), and LM(NO₃)₃ (M = Eu, Am).

Based on the theoretical analysis a new model is proposed that describes the mechanism of Ln³⁺ and An³⁺ extraction in two-phase system highly acidic water solution-organic solvent, according to which the formation of An³⁺ and Ln³⁺ complexes occurs at the water/organic interface as a substitution reaction of hydroxonium ion in a cavity of a protonated ligand for the metal cation.

Calculation results confirm the experimentally established higher extraction ability of dipicolinic acid diamides containing one aryl and one alkyl substituent at the amide nitrogen atoms compared to the N,N,N′,N′-tetraalkyl diamides (“effect of anomalous aryl strengthening”). Based on the simulation results the structure of the modified ligand L suggested that it should ensure maximum An³⁺/Ln³separation selectivity in the series of dipicolinic acid diamides.     

Extraction Behavior of Actinides and Metal Ions by the Promising Extractant,N,N,N′,N′-Tetraoctyl-3,6-dioxaoctanediamide (DOODA)

Abstract

The extraction of actinides, fission products, some non-nuclear elements, and nitric acid by N,N,N′,N′-tetraoctyl-3,6-dioxaoctanediamide (DOODA-C₈) in dodecane was extensively studied. Also studied was the extraction of HNO₃ and Nd(III) by the tetradodecyl analog of DOODA-C₈ in dodecane. Both extractants contain two ether oxygen atoms in the backbone chain carrying the two amide groups and can thus act as tetradentate ligands. The extractability of actinides decreases in the order Pu(IV) > U(VI), Am(III) > Np(V) in the extraction from nitric acid and Pu(IV) > Am(III) >> U(VI) in the extraction from perchloric acid. Ions of di-, tri-, tetra-, hexa-, and heptavalent metals strongly differ in the extractability by DOODA-C₈ but, except for lanthanides(III), there is no visible correlation of their distribution ratios with ionic radii. Due to the efficient extraction of actinides, weak extraction of fission products, and sufficient extraction capacity, DOODA-C₈ is a promising extractant for the recovery of minor actinides from high-level radioactive wastes.     

THE SYNERGISTIC SOLVENT EXTRACTION OF RADIUM FROM ALKALINE NITRATE MEDIA BY DICYCLOHEXANO-21-CROWN-7 COMBINED WITH 2-METHYL-2-HEPTYL NONANOIC ACID EQUtUBRIUM REACTIONS AND METAL ION COMPETITION∗

The equilibria in the solvent extraction of radium from aqueous sodium nitrate/sodium hydroxide solutions by toluene solutions of dicyclohexano-21-crown-7 (DC21C7). 2-methyl-2-heptylnonanioc acid (HMHN). and mixtures of the two reagents are examined. The mixed reagents are synergistic in the extraction of radium and selective for radium over other alkali and alkaline earth elements. The dependencies of the extraction on pH and reagent concentration were utilized in computer modeling to estimate the stochiometry of the extracted complexes and equilibria involved the extraction. Three organic-phase species were identified in the extraction under basic (pH 11-13) conditions. With A = MHN^?. B = DC21C7 and assuming NaA is a 10-fold aggregate they are. RaA₂B.NaA. Log K = 3.57: RaA NaA. Log K = 0.99: and B 2NaA. Log K = ? 0.41. The effect of the presence of various concentrations of sodium     

STUDIES ON EXTRACTION AND COORDINATION OF RARE EARTHS WITH β-KETOPHOSPHONATES

The rare earth extraction and coordination by three β-ke-tophosphonates with various structure, dibutyl 2-keto-2-phenyl-ethylphosphonate, (C₄H₉O)₂P(O)CH₂C(O)C₆H₅, (I), dibutyl 2-keto-pentylphosphonate, (C₄H₉O)₂P(O)CH₂C(O)C₃H₇, (II) and dibutyl 2-keto-3-methylbutylphosphonate, (C₄H₉O)₂P(O)CH₂C(O)CH(CH₃)CH₃, (III) from nitric acid medium have been described in this paper. The regularity of rare earth extraction with these β-ketophos-phonate reveals the same manner and resembles that of the common extractant, tributylphosphate (TBP). The extracted species has been deduced as Nd(NO₃)₃.3L and HNO₃-L by the slope method. By investigating the shift of P=0 and C=0 in IR spectra of the coordination compound prepared by saturated method, the predomination of P=0 has been established which coincides with the estimation from their extraction behavior.     

PARAFFIN WAX - TOPO,AN EXTRACT ANT FOR ACTINIDES AND LANTHANIDES

ABSTRACT

Paraffin wax - TOPO has been used for the extraction of Eu³⁺, Pu⁴⁺, and U0₂ ²⁺ from HN0₃ solutions at 65^° C. The extraction of Eu³⁺ increased with increasing TOPO percent in the wax phase but it decreased with increasing HNO₃ or Eu³⁺ carrier concentrations. The extraction of Pu4+ at tracer and U022+ between 2 to 10 mg (U)/ml from 0.5 to 1.0 M HN0₃ was almost quantitative while using 10 or 15% TOPO/wax at an aqueous to wax phase ratio of 1:1. In presence of uranyl ion, the extraction of Eu³⁺ decreased under all conditions. The best possible condition has been established and a scheme has been proposed for the separation of trivalent actinides and lanthanides, Pu⁴⁺ and U0₂ ²⁺ from their mixtures in laboratory wastes by using non-preequilibrated 15% TOPO/wax. The metal ions were individually stripped using various reagents. The easy phase separation from use of paraffin wax as the diluent makes the separation technique very simple.