Synthesis and copolymerization of methacryloyl hydroxamic acids

Three methacryloyl hydroxamic acids were prepared and homopolymerized yielding polymers which readily formed complexes with Fe³⁺. The amount of hydroxamic acid available for complexation was found to be low (29–32% of theoretical). Copolymers of methacryloyl hydroxamic acid with methyl methacrylate were also synthesized. The low amount of free hydroxamic acid functionality in the copolymers was ascribed to transfer reactions in the radical polymerization which resulted in branching and deactivation of the hydroxamic acid functionality. In addition, methacryloyl hydroxamic acid was copolymerized with N‐isopropyl acrylamide to yield thermotropic polymers capable of complexing with metal ions. At low concentrations of hydroxamic acid functionality, the lower critical solution temperature of the copolymers remained similar to that reported for poly(N‐isopropyl acrylamide). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 751–758, 2000     

Recovery of Plutonium(IV) from Aqueous Solutions Using Emulsion Liquid Membrane Containing 2‐Ethylhexyl Phosphonic Acid Mono‐2‐Ethylhexyl Ester as Ion Transporter

Abstract

An emulsion liquid membranes (ELMs) containing 2‐ethylhexyl phosphonic acid mono‐2‐ethylhexyl ester (H₂A₂) was tested for the extraction of plutonium(IV) from aqueous nitrate solutions of different compositions. Span 80 was used as the surface‐active agent and a mixture of 0.05 mol dm^?3 HNO₃+0.3 mol dm^?3 H₂C₂O₄ was used as the internal phase. Influence of some important experimental parameters such as exterior phase nitric acid concentration, ionic impurities in the exterior phase, concentration of H₂A₂ in ELM phase, and organic solvents on the ELM permeation process were systematically studied. The maximum efficiency of Pu extraction among group of experiments was 98% with permeability coefficient=0.508 min^?1, and the corresponding concentration factor of Pu in the receiving phase was ca. 10. The stability of the emulsions was tested in the presence of different organic solvents and at different concentrations of Span 80 in LM phase. The extractions of Pu by ELM from actual and simulated waste solutions as well as in presence of some added ionic impurities were investigated. Rate of Pu extraction by ELM was studied at different treatment ratios and under repeat extractions by the same emulsion. The repeat extraction experiments showed that a concentration factor of more than 80 for Pu could be achieved.     

Studies on the Extraction of Actinides Using a Solvent Containing D2EHiBA in Room Temperature Ionic Liquids: Unusual Extraction of the Tetravalent Ions

The extraction behavior of U(VI), Pu(IV), and Np(IV) from nitric acid medium has been studied using branched chain di(2-ethylhexyl)isobutyramide (D2EHiBA) dissolved in different room temperature ionic liquids (RTILs) [C_nmim][NTf₂] (where n = 4, 6, or 8). Uranium extraction (D_U) increased gradually with aqueous phase acidity for the three RTILs used in this study suggesting solvation mechanism. There was a reversal in the extraction behavior of Pu(IV) and Np(IV) from nitric acid medium using D2EHiBA dissolved in RTILs as solvents as compared to the behavior reported in the molecular diluent, n-dodecane, which shows negligible extraction of these metal ions. The extraction of Pu(IV) increased with aqueous phase acidity in different RTILs in the order: [C₈mim][NTf₂] > [C₆mim][NTf₂] > [C₄mim][NTf₂]. The distribution ratio values of these metal ions followed the order: D_Pu(IV) ≥ D_Np(IV) > D_U(VI) using D2EHiBA as extractant suggesting that RTILs can modify the extraction behavior of extractants.     

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.     

Synergistic Extraction of Plutonium (IV) from Nitric Acid Medium by Mixtures of TOPO and HTTA

Abstract

Synergistic solvent extraction of Pu(IV) from nitric acid medium by mixtures of thenoyltrifluoroacetone (HTTA) and tri-n-octylphosphine oxide (TOPO) in benzene was investigated by a method developed for such studies. The species involved in the extraction were identified as Pu(NO₃)₄ · 2TOPO, Pu-(N0₃)₃(TTA) · 2TOPO, Pu(NO₃)₂(TTA)₂ · TOPO, and Pu(NO₃)(TTA)₃ · TOPO. The concentration equilibrium constants for the extraction of all the suggested species from 1.0 M nitric acid were calculated from the data obtained, and the concentration equilibrium constants for their formation in the organic phase were estimated.     

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).     

Extraction of Benzene and Naphthalene Carboxylic Acids Using Quaternary Ammonium Salts As a Model Study for the Separation of Coal Oxidation Products

Abstract

The ion‐pair solvent extraction of benzene‐ and naphthalene‐carboxylic acids has been investigated as a model study for the separation of coal oxidation products, which are formed by treatment with alkaline solutions at high temperatures. It was possible that benzene‐ and naphthalene‐dicarboxylic acids are extracted into several types of organic solvents with quaternary ammonium ions. The extraction equilibrium constants (K_ex) for benzoic acid, 1,2‐benzenedicarboxylic acid, 1,3‐benzenedicarboxylic acid, 1‐naphthoic acid, 2‐naphthoic acid, 2,3‐naphthalenedicarboxylic acid, and 2,6‐naphthalenedicarboxylic acid into chloroform were determined at 20°C. The difference of K_ex among the aromatic acids was sufficiently large for designing a separation method for these aromatic acids. It was unexpected that the extraction of dicarboxylic acids was slower than that of monocarboxylic acids, although the ion‐pair formation of aromatic carboxylate ion with quaternary ammonium ion is normally considered as a diffusion control reaction in aqueous phase. Thus, this fact suggests that the phase transfer of the ion‐pair from aqueous to organic phase is the rate‐determining step. Liner‐free‐energy relationship was observed for the monocarboxylic acids using different quaternary ammonium salts while that was ambiguous for the dicarboxylic acids. This is due to the steric influence of the counter ions for the magnitude of K_ex.     

Heterocyclic Hydroxamic Acids. VI. Microdetermination of Cerium(IV) with N-p-Chlorophenyl-2-furohydroxamic Acid

Abstract

N-p-Chlorophenyl-2-furohydroxamic acid is presented as the most sensitive and selective of the hydroxamic acids reported so far for the separation-spectrophotometric determination of cerium(IV). Cerium was determined in lanthanum oxide.     

Small‐Angle Neutron Scattering Study of Plutonium Third Phase Formation in 30% TBP/HNO3/Alkane Diluent Systems

Abstract

Third phase formation in the extraction of Pu(IV) nitrate by 30% tri‐n‐butyl phosphate (TBP) dissolved in n‐dodecane or in the highly branched diluent hydrogenated polypropylene tetramer (HPT), which may also be known as 4,4 dipropyl heptane or tétrapropylène hydrogéné, was investigated through small‐angle neutron scattering (SANS) measurements. The SANS data were interpreted using the Baxter model for hard‐spheres with surface adhesion. According to this model, the increase in scattering intensity observed when increasing amounts of Pu(NO₃)₄ are extracted into the organic phase, is due to interactions between small reverse micelles containing three to five TBP molecules. In n‐dodecane, the micelles interact through attractive forces between their polar cores with a potential energy of up to ?2.6 k_BT. This strong intermicellar attraction leads to organic phase splitting with the separation of most of the solutes of the original organic phase into a distinct phase containing interspersed layers of n‐dodecane. When HPT is the diluent, the intermicellar attraction energy calculated from the SANS data is much lower, and no third phase formation is observed under comparable chemical conditions. However, when a significant amount of the initial aqueous plutonium is in the form of plutonyl ions, PuO₂ ²⁺, the critical energy potential is reached even in HPT. A potential explanation of the effect of Pu(VI) involves the formation of a plutonyl trinitrato complex.     

Solvent Extraction Investigations on Pu(IV) and Th(IV) Complexes with Hydrophilic SO3-Ph-BTP and SO3-Ph-BTBP Ligands

ABSTRACT

Complexation of Pu(IV) and Th(IV) cations by the title ligands – hydrophilic sulfophenyl triazinyl derivatives of bis-triazinyl-pyridine and -bipyridine – was studied in solvent extraction systems containing a TODGA extractant and one of these hydrophilic ligands. Stoichiometries and stability constants of the complexes formed in an acidic (HNO₃) aqueous phase have been determined. The Pu(IV) complexes are significantly stronger than their Th(IV) analogues. Only two complexes of each metal with SO₃-Ph-BTP (1:1 and 1:2) have been detected, and only one (1:1) with SO₃-Ph-BTBP; both numbers being less than expected based on the coordination numbers of the metal ions and on the denticities of the ligands. Possible reasons of this discrepancy are discussed.     

Solvent Extraction and Spectrophotometric Studies on Synergistic Extraction of Plutonium(IV) by Mixtures of Thenoyltrifluoroacetone (HTTA) and Tri-n-butylphosphate (TBP) in Benzene

Abstract

The synergistic extraction of Pu(IV) from perchloric acid solutions into mixtures of thenoyltrifluoroacetone (HTTA) and tri-n-butylphosphate (TBP) in benzene was investigated by solvent extraction methods. The adduct responsible for synergism was found to be Pu(TTA)₄·TBP. The adduct formation between Pu(TTA)₄ and TBP in the benzene phase was also investigated by spectrophotometry. The equilibrium constants for the equilibria involved were obtained both by solvent extraction and by spectrophotometric methods.     

UPTAKE OF METAL IONS BY A NEW CHELATING ION-EXCHANGE RESIN. PART 1: ACID DEPENDENCIES OF ACTINIDE IONS*

ABSTRACT

The uptake of several actinide ions [U(VI), Pu(IV), Np(IV), Th(IV] and Am(DI)) from nitric and hydrochloric acid solutions, and of U(VI) from near-neutral solutions by the new chelating ion-exchange resin, Diphonix^TM, has been investigated. Diphonix is a polyfunctional resin containing sulfonic and gem-diphosphonic acid groups chemically bonded in a styrene-divinylbenzene polymeric network. Comparison of the acid dependencies of the actinide ions uptake measured with Diphonix with those obtained using a commercial sulfonic -type resin and a resin containing both sulfonic and monophosphonic aCid groups, hat Shown that Diphonix binds the actinides via a different kind of chemical interaction, involving the.formation of chelate complexes through the phosphoryl groups of the gem-diphosphonic acids. As a consequence, Diphonix is superior to other resins in extracting actinide ions from very acidic solutions. A better performance of Diphonix is also observed with the uptake of uranium from neutral solutions. Conditions for efficient stripping of actinide species from the resin have been found.     

Synthesis and characterization of poly(hydroxamic acid) chelating resin from poly(methyl acrylate)‐grafted sago starch

A new chelating ion‐exchange resin containing the hydroxamic acid functional group was synthesized from poly(methyl acrylate) (PMA)‐grafted sago starch. The PMA grafted copolymer was obtained by a free‐radical initiating process in which ceric ammonium nitrate was used as an initiator. Conversion of the ester groups of the PMA‐grafted copolymer into hydroxamic acid was carried out by treatment of an ester with hydroxylamine in an alkaline solution. The characterization of the poly(hydroxamic acid) chelating resin was performed by FTIR spectroscopy, TG, and DSC analyses. The hydroxamic acid functional group was identified by infrared spectroscopy. The chelating behavior of the prepared resin toward some metal ions was investigated using a batch technique. The binding capacities of copper, iron, chromium, and nickel were excellent and the copper capacity was maximum (3.46 mmol g⁻¹) at pH 6. The rate of exchange of the copper ion was very fast that is, t_1/2 < 5 min. It was also observed that the metal ion‐sorption capacities of the resin were pH‐dependent and its selectivity toward the metal ions used is in the following order: Cu²⁺ > Fe³⁺ > Cr³⁺ > Ni²⁺ > Co²⁺ > Zn²⁺ > Cd²⁺ > As³⁺ > Pb²⁺. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1256–1264, 2001     

Extraction Behavior of Some Actinides and Fission Products from Nitric Acid Medium by a New Unsymmetrical Diglycolamide

Abstract

A new unsymmetrical diglycolamide, N,N-di-2-ethylhexyl-N',N'-di-octyl-3-oxapentane-1,5-diamide, trivially known as di-ethylhexyl-di-octyl-diglycolamide (DEHDODGA) has been synthesized, and characterized by ¹H, and ¹³C nmr, mass, and IR spectroscopy. Extraction behavior of ²⁴¹Am(III), ^(152+154)Eu(III), ²³⁹Pu(III), ²³⁹Pu(IV), ²³³U(VI), ¹³⁷Cs(I), and ^(85+89)Sr(II) from nitric acid medium by a solution of DEHDODGA in n-dodecane was studied, at 298–333 K. The effect of concentrations of HNO₃ and DEHDODGA and of temperature on the distribution ratio (D _M) was studied. Extraction of Eu(III), Am(III), Pu(III), and Pu(IV) increased with increase in nitric acid concentration, and the distribution ratio of Cs(I) was insignificant. However, the distribution ratios of U(VI) and Sr(II), though not insignificant, but was quite less compared to trivalents, and Pu(IV). The D _Sr(II) increased with increase in the concentration of nitric acid, reaching a maximum at 4 M followed by decrease. The stoichiometry of Am(III) – DEHDODGA was determined by slope analysis of extraction data, and the enthalpy change accompanied by the extraction of Eu(III), Pu(III), and Am(III) was determined and reported in this article.     

EXTRACTION OF U(VI), Pu(IV) AND Th(IV) BY SOME TRIALKYL PHOSPHATES

ABSTRACT

This paper reports the data on the extraction of U(VI), Pu(IV) and Th(IV) from nitric acid by tri-isobutyl phosphate, tri-n-amyl phosphate, tri-isoamyl phosphate and tri-n-hexyl phosphate and provides a comparison of their extract ion behaviour with that of tri-n-butyl phosphate. Data on the third phase formation in the system Th(NO₃) ₄ ^?HNO₃ ^?1.1 M trialkyl phosphate/n-dodecane are also presented.     

UPTAKE OF METAL IONS BY A NEW CHELATING ION-EXCHANGE RESIN. PART 4 : KINETICS

Abstract

The rate of uptake of several actinide ions [Am(III), U(VI), Th(IV), Np(IV) and Pu(IV)] and of some transition-metal ions [Co(II), Zn(II), Fe(III) and Cr(III)] at tracer concentration level, from solutions of various compositions, by the new chelating ion-exchange resin, Diphonix^Tm, has been investigated. Diphonix is a polyfunctional resin containing sulfonic and gem-diphosphonic acid groups chemically bonded in a styrene-divinylbenzene polymeric network. It binds actinide and other ions through the formation of chelate complexes with the phosphoryl groups of the gem-diphosphonic acids. The experiments discussed in this work have allowed us to establish the paramount importance of the presence of the sulfonic groups in obtaining practically useful rates of metal ions uptake. Comparison of the kinetic behavior of Diphonix with that of commercial sulfonic-type resins has shown that Diphonix reacts with the investigated ions as rapidly as do the other resins. Conditions for efficient and rapid stripping of all the investigated cations, including Cr(III), have been found.     

Ionic Liquid Extractants in Molecular Diluents: Extraction Behavior of Plutonium (IV) in 1,3-Diketonate Ionic Liquids

Abstract

Room temperature ionic liquids (RTILs) containing β-diketonate anions have been prepared and studied for the extraction of ²³⁹Pu(IV), ²³³U(VI), and ²⁴¹Am(III) from nitric acid medium. The ionic liquids such as alkylquaternaryammonium thenoyltrifluoroacetonate (R₄NTTA), and 1-alkyl-3-methylimidazolium thenoyltrifluoroacetonate (amimTTA), with methyl, butyl, hexyl, heptyl, and octyl moieties have been prepared and characterized by ¹H and ¹³C nmr and IR spectroscopy. The distribution ratio of plutonium(IV) (D _Pu(IV)) in a solution of tri-n-octylmethylammonium thenoyltrifluoroacetonate (TOMATTA) present in tri-n-octylmethylammonium bis(trifluoromethylsulfonyl)imide (TOMANTf₂) and amimTTA in amimNTf₂ was studied as a function of various parameters. The unique property of β-diketonate ionic liquids, namely, the miscibility in molecular diluents, was exploited to elucidate the mechanism of Pu(IV) extraction in these ionic liquids.     

Synthesis and Evaluation of N,N′-dimethyl-N,N′-dicyclohexyl-Malonamide (DMDCMA) as an Extractant for Actinides

A malonamide based extractant, i.e., N,N′-dimethyl-N,N′-dicyclohexyl-malonamide (DMDCMA) was synthesized in a single step and tested for the extraction of several actinide ions such as Am(III), U(VI), Np(IV), Np(VI), Pu(IV), Pu(VI), etc., from nitric acid medium. The extractant was soluble in phenyltrifluoromethylsulphone (PTMS or FS-13) unless stated otherwise. The effect of various experimental parameters, such as the aqueous phase acidity (0.01–3 M HNO₃), nature of the acid, oxidation states of the metal ions, ligand concentration, nature of the diluent and temperature on the extraction behavior of metal ions was studied. The extracted Am(III) species was determined from slope analysis method as [Am(NO₃)₃(DMDCMA)₂]. The extraction of the metal ions was found to increase with the aqueous phase acidity. The temperature variation studies allowed the calculation of the heat of the two-phase extraction reaction as well as the corresponding extraction constants. These studies revealed that DMDCMA showed good extraction for all the actinide metal ions investigated, and have the advantage of single stage synthesis and easier purification protocol.     

Studies on the Extraction of Actinides by Diamylamyl Phosphonate

Abstract

Diamylamyl phosphonate (DAAP) was synthesised by the Michealis Becker reaction, and was characterized by elemental analysis, IR, and ³¹P NMR. The extraction of U(VI), Th(IV), Pu(IV) and Am(III) by 1.1 M DAAP in n‐dodecane as a function of nitric acid concentration was studied and the results are compared with the extraction behavior of these ions by tributyl phosphate (TBP) and triamyl phosphate (TAP) in n‐dodecane. Some important physical properties of the extractant that have to be met for its use in industrial scale liquid‐liquid extraction such as density, surface tension, viscosity and phase disengagement time with 1.1 M DAAP/n‐dodecane have been measured and compared with those of 1.1 M TBP/n‐dodecane. Studies on the third phase formation behavior of DAAP/n‐dodecane with U(VI) and Th(IV) nitrates in nitric acid medium have been carried out and the results are reported. The breakthrough and elution behavior of U(VI) using a column packed with 50% (w/w) DAAP impregnated on Amberlite XAD‐7 was studied and reported.     

The Role of Hydroxamic Acids in the Retention of Fission Products in TBP Diluents. A Quantitative Study in a Model System

Abstract

The degradation with nitric acid of kerosene-type diluents of TBP in the reprocessing of nuclear fuel leads to the formation of primary nitroalkanes. These, under acid conditions, may hydrolyze to hydroxamic acids, HA, which are well-known complex-ing agents of many metal ions, including ⁹⁵Zr. The formation of very stable HA-⁹⁵Zr complexes has been proposed as a rationale for the retention of ⁹⁵Zr in the diluents. However, the results of this study carried out in a model system, the acid-catalyzed conversion of 1-nitropropane to propanhydroxamic acid, and the subsequent hydrolysis to carboxylic acid and hydroxylamine—easily extensible to the actual reprocessing processes—indicate that in these systems the equilibrium concentration of hydroxamic acids attainable is too low (10^?8 to 10^?9 M) to account for the “zirconium retention” phenomenon.