THE EQUILIBRIUM REACTION OF THE EXTRACTION OF URANIUM(VI) WITH DI-(2-ETHYLHEXYL) PHOSPHORIC ACID FROM NITRIC ACID SOLUTIONS

The equilibrium reactions for the extraction of uranium(VI) with di(2-ethylhexyl)phosphoric acid from nitric acid solutions is investigated. In this work, proton NMR technique was used to verify that the nitrate ligand in the resulting complexes originated from the complexing of nitric acid. Organic solutions of 0.05 M (dimeric HDEHP, the upper bar denotes the species in the organic phase) in kerosene were used to extract aqueous solutions containing various concentrations of uranyl nitrate and nitric acid. The concentrations of nitric acid and uranium(VI) in the organic phase were measured, and used to determine the composition of the resulting complex. Which were found to be varied with the uranium(VI) loading and the nitric acid loading of HDEHP. Parallel reactions of forming UO were proposed to describe this extraction system. The proposed reactions elucidate the equilibrium behavior consistently, for the loadings of uranium(VI) and nitric acid ranging from very low value to the vicinity of saturation.     

POLYNITROGEN REAGENTS IN METAL SEPARATION. PART 1. DITERTIARY AND DIQUATERNARY AMMONIUM EXTRACTANTS FOR COBALT(II) AND COPPER(II) IN HCl MEDIUM.

Abstract

A variety of alkyldiammonium extractants (tertiary and quaternary)were prepared, characterised and used to extract cobalt(II) and copper(II) from HCl medium. These extractants were compared with Aliquat-336 and Alamine-336. The diammonium derivatives of ethylene diamine proved to be superior to their mono analogues.     

DILUENT EFFECT ON THE EXTRACTION OF URANIUM(VI) FROM HYDROCHLORIC ACID SOLUTIONS BY TRIOCTYLMETHYLAMMONIUM CHLORIDE

ABSTRACT

The extraction of uranium(VI) from hydrochloric acid solutions by trioctylmethylammonium chloride (TOMAC) has been examined using various diluents such as benzene, chlorobenzene, o-dichlorobenzene, toluene, m-xylene, nitrobenzene, carbon tetrachloride, chloroform and 1,2-dichloroethane. It was found that by assuming a regular solution, the distribution coefficient and the enthalpy change associated with the metal extraction can be expressed in terms of the solubility parameter of TOMAC, diluent and the complex formed in the organic phase and their molar volumes. Additionally an empirical relation holds between distribution coefficient and the viscosity of diluent. Further results for the extraction of divalent manganese, cobalt, copper, zinc and cadmium from hydrochloric acid solutions by TOMAC are investigated in comparison with those of uranium(VI).     

SOLVENT EXTRACTION OF URANIUM( VI) AND THORIUM( IV) FROM NITRATE MEDIA BY CARBOXYLIC ACID AMIDES

ABSTRACT

A series of nineteen N-alkyl carboxylic acid amides (R.CO.NHR') has been prepared, in which the alkyl groups R and R' have been varied in order to introduce different degrees of steric complexity into the compounds. A smaller number of N,N-dialkyl amides (R.CO.NR₂) and non-substituted amides (R.CO.NH₂) has also been prepared for comparison purposes. These amides were characterized by measurement of their boiling points, melting points, refractive indices and densities.|The solvent extraction of uranium(VI) and thorium(IV) from sodium nitrate media by solutions of the amides in toluene was studied. Increasing steric bulk of the alkyl groups R and R' was found to cause a marked decrease in the extraction of thorium, with a much smaller effect on the extraction of uranium, thus considerably enhancing the separation between these metals. Vapour pressure osmometry studies indicate that the N,N-alkyl amides are self-associated in toluene solution, with aggregation numbers up to about 2.5 for 0.6 M solutions at 35°C. In contrast, the N,N-dialkylamides behave as monomers under these conditions. The distribution ratios for the extraction of uranium and thorium show second- and third-order dependences, respectively, on the extractant concentration for both the N-alkyl and N,N-dialkyl amides.     

NITROGEN REAGENTS IN METAL ION SEPARATION. PART IX. EXTRACTION OF COBALT AND NICKEL USING IMIDAZOLE DERIVATIVES

ABSTRACT

The extraction capability of derivatives of imidazole towards Co(II) and Ni(II) has been investigated in dilute acid medium in the presence of each of chloride, perchlorate and thiocyanate ions. The influence of the stereochemistry of the substituted imidazole on the extraction behaviour has been investigated. Two-phase potentiometric titrations were employed to determine the nature of the metal species extracted into the organic phases. The electronic spectra of the extracted metal species have been employed to provide information of the nature of such species.     

SOLVENT EXTRACTION OF NITRIC,HYDROCHLORIC AND SULFURIC ACID AND THEIR URANYL SALTS WITH TRI-n-OCTYLPHOSPHINE OXIDE

ABSTRACT

The equilibrium constants of the extraction of nitric, hydrochloric and sulfuric acid and of their uranyl salts with trl-n-octylphoophlne oxide (TOPO), dissolved In different diluents, have been determined. Obtained extraction constants have been correlated with the corresponding dissociation constants of mineral aclda used. The more mineral acid dissociated, the less undlssoclated molecules of acid available and, as a consequence, the extraction process is less expressed.     

NITROGEN REAGENTS IN METAL ION SEPARATION. PART VIII SUBSTITUTED IMIDAZOLES AS EXTRACTANTS FOR Cu3+

ABSTRACT

A number of derivatives of imidazole have been synthesized. Their extraction behaviour towards Cu²⁺ in dilute acid medium have been investigated in both chloride and perchlorate media. The influence of electronic and stereochemical effects are discussed. Two-phase potentiometric titrations were employed to determine the two-phase protonation constants and Cu(II) complex species present in the organic phases. The N-decylimidazole derivative has a higher extraction efficiency than the other C-ring substituted imidazoles in spite of their greater protonation constants.     

EXTRACTION MECHANISM OF Sc(III) AND SEPARATION FROM ThUV).Fe(III) AND Lu(III) WITH BIS(2,4,4-TRIMETHYLPENTYL)PHOS- PHINIC ACID IN N-HEXANE FROM SULPHURIC ACID SOLUTIONS

ABSTRACT

The extraction equilibrium data of sulphuric acid and scandium(III) with bis(2,4,4-trimethylpenty)phosphinic acid (H[BTMPP]) from sulphuric acid solutions have been obtained. There are two extraction mechanisms of scandium(III) with H[BTMFP] at different ranges of aqueous acidity. The extraction of Sc(III) proceeds according to a cation exchange reaction at lower aqueous acidity and to a solvating reaction at higher acidity. The practicability of separating Sc(III) from Th(IV),Fe(III) and Lu(II) by controlling the aqueous acidity was discussed. The effect of temperature on extraction of Sc(III) was observed and thermodynamic, functions were caculated. IR and NMR spectra were made for organic extracts. The extraction characteristics of H[BTMPP] and di(2-ethylbexyl)phosphinic acid (H[DEHP]) were contrasted to obtain more information about extraction with H[BTMPP].     

EXTRACTION OF URANIUM(IV,VI), PLUTONIUM(III) AND NITRIC ACID BY 30% TRIBUTYL PHOSPHATE (TBP) IN DODECANE

Abstract

Data on the distribution of uranium(IV,VI), plutonium(III) and nitric acid between 30 vol.% TBP in dodecane and aqueous nitrate solutions also containing hydrazine nitrate were mathematically described by empirical equations. This made it possible to present distribution ratios of the extracted components as functions of concentrations and temperature at a single variable being varied and other variables being kept constant. Salting-out and self-salting-out action of the electrolytes present in the system as well as mutual replacement of the extracted components from the organic phase are shown.     

DISTRIBUTION BEHAVIOUR OF U(VI), Th(IV) AND Pa(V) FROM NITRIC ACID MEDIUM USING LINEAR AND BRANCHED CHAIN EXTRACTANTS

ABSTRACT

The extraction behaviour of 1M solutions of tri-2-ethylhexyl phosphate (TEHP), di-2-ethyl hexyl isobutyramide (D2EHIBA), tri-n-butyl phosphate (TBP) and di-n-hexyl hexanamide (DHHA) in n-dodecane towards U(VI), Th(IV) and Pa(V) in the presence of 220 g/L of Th from nitric acid medium has been studied. The limiting organic concentrations (LOC) of thorium (g/L) for 1 M TBP and 1 M DHHA are evaluated as 31, 20 ( at 1 M HNO₃) and 25,13 (at 4 M HNO₃) respectively. The distribution ratio (D) values of U(VI), Th(IV) and Pa(V) in the presence of thorium (220 g/L) at. 1 M HNO₃ suggest that branching in the alky group of amides suppresses the extraction considerably. In view of the selective extraction of U over Th by 5 % TBP in THOREX process at 4 M HNO₃, distribution behaviour is also studied employing a lower concenfration (0·18 M) of extractant for comparison purpose, Separation factor (S. F.) values for U(VI) over Th(IV) under different experimental conditions consistently varied in the order: D2EHIBA > DHHA > TEHP > TBP. The quantitative extraction of ²³³U from a synthetic mixture containing ²³³U (10^?5 M). ²³³Pa (10^?11 M) and thorium (220 g/L) at 1 M HNO₃ using 1 M solution of D2EHIBA in n-dodecane is achieved in three stages, Stripping and reusability studies of D2EHIBA have also been carried out.     

EXTRACTION OF Am FROM NITRIC ACID BY CARBAMOYL-PHOSPHORYL EXTRACTANTS: THE INFLUENCE OF SUBSTITUENTS ON THE SELECTIVITY OF Am OVER Fe AND SELECTED FISSION PRODUCTS

A number of neutral extractants containing the P(0)(CH₂)_nC(0)N raolety were evaluated for their ability to extract Am from nitric acid and their selectivity for Am over Fe and selected fission products. Extractants containing alkoxy, alkyl, and aryl substltuents were evaluated. Tetrachloroethylene was used as a diluent. Fission products selected for study were Y, Zr, Mo, Tc, Ru, Rh, Pd, La, Ce, Pr, Nd, Sra, and Eu. The conclusions drawn were that the most efficient and selective Am extractant contains a single carbon bridging group, one or two phenyl groups attached to the phosphorus atom and l9obutyl groups attached to the amide nitrogen.     

EFFECT OF EXTRACTANT STRUCTURE ON THIRD PHASE FORMATION IN THE EXTRACTION OF URANIUM AND NITRIC ACID BY N,N-DIALKYL AMIDES

The influence of the molecular structure of amides on the third phase formation in the extraction of uranium and nitric acid was investigated. Nine amides namely, dibutyl hexanamide (DBHA), diisobutyl hexanamide (DiBHA), dibutyl octanamide (DBOA), dihexyl hexanamide (DHHA), dibutyl dodecanamide (DBDA), diiso-octyl butanamide (DiOBA), di n-octyl isobutanamide (DOiBA), di n-octyl butanamide (DOBA), and di n-octyl hexanamide (DOHA) were synthesized and used. The limiting organic concentration (LOC) of uranium (VI) for third phase formation was studied as a function of nitric acid concentration using 0.5 M solutions of these amides in dodecane. The LOC for extraction from neutral medium (with near zero free acidity) was also measured at four different temperatures. The LOC values were found to increase in general with an increase in the total number of carbon atoms in the amide from 14 to 22. The LOC values of DBHA (C. No. 14), DiBHA (C. No. 14), DBOA (C. No. 16) were lower compared to that of DHHA (C. No. 18), DBDA (C. No. 20), DOHA (C. No. 22), which have relatively longer carbon chain length. Further it was observed that introduction of branching at the nitrogen side increases the LOC value as compared to the straight chain analogue, as in the case of DiOBA and DiBHA. In the latter case, however, this effect is not very pronounced perhaps due to the smaller carbon chain length. Introduction of branching at the position alpha to the carbonyl group was found to sharply decrease the LOC value due to steric hindrance as can be seen in the case of DOBA and DOiBA. Further, by varying the carbon chain length on both acyl and nitrogen sides, keeping the total carbon number invariant, it was found that the LOC increases considerably on increasing the chain length on the acyl side. On the contrary, the LOC for nitric acid extraction was not influenced significantly by the structure of the amide. Nevertheless, the distribution ratio at the point of dissolution of the third phase was found to decrease with introduction of branching on either end of the amide and more so, if branching was introduced on the acyl end of the amide.     

REMOVAL OF NITRIC ACID FROM CONCENTRATED PHOSPHORIC ACID BY EXTRACTION WITH METHYL ISOBUTYL KETONE IN AROMATIC DILUENTS

The extraction of nitric acid from concentrated phosphoric acid solutions by methyl isobutyl ketone (MIBK) dissolved in aromatic diluent has been studied. Nitric acid can be effectively removed by MIBK from the solutions containing 50–75% H₃P0₄. With increasing the concentration of either H₃PO₄ or MIBK, the distribution coefficient of HN0₃ increases but the separation factor for HN0₃ against H₃PO₄ decreases. However, it is possible to achieve a complete removal of HN0₃ in a few of stages and the coextraction of H₃PO₄ can be limited to less than 1%.     

EXTRACTION OF GOLD fill) FROM HYDROCHLORIC ACID SOLUTIONS BY TRI-ISOBUTYL PHOSPHINE SULFIDE IN TOLUENE.

The extractant th-isobutyl phosphine sulfide (TIBPS ), Cyanex 471, in toluene has been investigated for the extraction of Au (III) from aqueous HCI solutions. Analysis of the equilibrium data shows that the extraction proceeds via a solvating type mechanism by the formation of the species AuCI3.FI and AuCl₃.2R, for which formation constants are log 677 β= 34.84 and log β= 42.04 respectively (R =TIBPS).     

THE EFFECT OF TEMPERATURE ON THE SYNERGISTIC EXTRACTION OF THORIUM( IV) AND URANIUM( VI) BY 2-ETHYLHEXYL PHENYLPHOSPHONIC ACID AND MICELLES OF DINONYL NAPHTHALENE SULPHONIC ACID

ABSTRACT

The influence of temperature in the range 15 to 75° C on the extraction of thorium( IV) and uranium( VI) from nitric acid solutions into ligroine solutions of 2-ethylhexyl phenylphosphonic acid ( HEHφ P) micellar dinonyl naphthalene sulphonic acid ( HDNNS) extractants and mixture of the two extractants is reported. From the variation of the distribution ratio with temperature, the enthalpy changes associated with the extraction were determined, and an attempt was made to estimate the free energy and entropy changes associated with the extraction process. The results indicate that the extraction of thorium is favored by both entropy change and enthalpy change when the solvent is HEHφ P and the mixture of HEHOP and HDNNS, but entropy controlled when HDNNS is the extractant. On the other hand, the extraction of uranium by HEHφ P is enthalpy controlled but favored by entropy change when the solvent is HDNNS or a mixture of the two ligands. Temperature did not affect the extraction stoichiometry.     

EXTRACTION OF STOONTIUM FROM NITRIC ACID SOLUTIONS USING DICYCLOHEXANO-18-CROWN-5 AND ITS DERIVATIVES

Dicyclohexano-18-Crown-6 (DCH18C6)and its dimethyl and di-t-butyl derivatives have been evaluated as extractants for Sr (II) from nitric acid media. As with DCH18C6, a correlation is observed between the extraction of strontium nitrate by the di-t-butyl compound dissolved in a variety of oxygenated, aliphatic solvents and the concentration of water in the organic phase. Comparison of the extractant dependencies of the three compounds using n-octanol as the diluent shows that the expected first power dependence of the strontium distribution ratio (Dsr) on crown concentration is observed only for the di-t-butyl derivative. DCH18C6 shows a marked deviation from first power dependence at crown concentrations greater -0.01 M. Dsr acid dependencies for DCHl8C6 and the di-t-butyl derivative do not exhibit the decrease in strontium distribution ratios at high acidities observed for DCH18C6 in chlorinated hydrocarbons.     

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.     

THE EFFECT OF TEMPERATURE ON THE EXTRACTION OF NITRIC ACID AND PLUTONIUM(IV) NITRATE WITH 30 VOL.% TRIBUTYL PHOSPHATE (TBP)

Abstract

Own and published data were evaluated for characterizing the effect of temperature on the distribution of nitric acid and plutonium(IV). The solutes were distributed between 30 vol.% TBP in an aliphatic diluent and aqueous solutions containing nitric acid and zero to macro amounts of plutonium(IV) and uranyl nitrates. The temperature dependence of the distribution ratios is described with empirical model equations and examples of the dependence in the absence and presence of uranium(VI) are given. Taking infinite dilution of all solutes of the system as a standard state, the enthalpy change of the extraction reaction could be estimated as ?17 kJ/mol for nitric acid but no numerical estimate was possible for plutonium(IV).     

STUDIES ON THE EXTRACTION OF PLUTONIUM(IV) FROM AQUEOUS NITRIC ACID - OXALIC ACID BY ALIQUAT-336

ABSTRACT

The extraction of Pu(IV) by Aliquat-336 from aqueous nitric acid containing oxalic acid was studied with a view to exploring the feasibility of recovery of Pu(IV) from Pu(IV) oxalate precipitation effluents. Distribution ratio data were obtained as a function of concentration of nitric acid, oxalic acid and Aliquat-336. The data obtained revealed that Pu(IV) can be extracted almost quantitatively by 20% Aliquate-336 in xylene from aqueous medium containing oxalic acid up to 0.25 M provided the nitric acid concentration is ≥ 4 M. These data suggest that Pu(IV) can be recovered directly from nitric acid - oxalic acid waste generated in Pu-oxalate precipitation by Aliquat-336 extraction.