Synergistic Extraction of U(VI), Th(IV), and Lanthanides(III) from Nitric Acid Solutions Using Mixtures of TODGA and Dinonylnaphthalene Sulfonic Acid

The extraction of U(VI), Th(IV), and lanthanides(III) from aqueous nitric acid solutions with mixtures of N,N,N′,N′-tetra(n-octyl)diglycolamide (TODGA) and dinonylnaphtalene sulfonic acid (HDNNS) in n-decane has been investigated. The extraction efficiency of U(VI), Th(IV), and Ln(III) ions is greatly enhanced by addition of HDNNS to an organic phase containing TODGA. The synergistic effect arises from the higher hydrophobicity of U(VI), Th(IV), and Ln(III) extracted species formed by TODGA and DNNS^? anions as compared to those formed by TODGA and NO₃^? ions as counter anions. The synergistic effect for U(VI), Th(IV), and Ln(III) extraction from aqueous nitric acid solutions with mixtures of TODGA and HDNNS becomes weaker when the acidity of the aqueous phase increases. A high synergistic enhancement is accompanied with a high selectivity of Ln(III) extraction from nitric acid solutions.     

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).     

Adsorption of Uranium(VI) and Zirconium(IV) from Acid Solutions on Silica Gel

Abstract

Adsorption of uranium(VI) and zirconium(IV) from aqueous solutions on silica gel was investigated by the batch equilibration method. The influence of shaking time and concentrations of nitric acid (i.e., pH of solution) and metal ions in solution were studied. Adsorption of uranium(VI) and zirconium(IV) increases with an increase of pH (decrease of nitric acid concentration) and ion concentrations. The adsorption mechanism of uranium(VI) and zirconium(IV) from aqueous solutions on silica gel is proposed. It is shown that zirconium(IV) and uranium(VI) can be separated if the concentration of nitric acid in solution is higher than 0.01 mol/dm³.     

Selective Separation of Uranium using Alizarin Red S (ARS)-Modified Anion-Exchange Resin or by Flotation of U-ARS Chelate

ABSTRACT

An alizarin red S (ARS)-modified anion-exchange resin was prepared by a simple reaction of ARS with the anion exchanger Doulite A101 and used for the efficient sorption of uranium from aqueous media. The effect of various parameters on the sorption of U(VI) (pH effect, sorption kinetics, resin capacity and breakthrough curves) was investigated. The modified resin sorbs U(VI) over a wide range of pH (2·8–5) with a maximum sorption capacity of 0·68 mmol.g^?1 at pH 3·2 to 4·0. Iron (III), Zr(IV), Ti(IV), Cu(II), and Th(IV) ions are also sorbed to different extents, but Be(II), Bi(III), Ca(II), Mg(II), Pb(II), Hg(II), Zn(II), Cd(II), AI(III), Mn(II), Co(II) and Ni(II) are not sorbed; thus, conditions for separating U(VI) from these metal ions have been identified. For eluting U(VI) from the resin, 0·2 mol.L^?1 HCl was used and the recovery recorded was as high as 99.9%. The use of ARS is extended to float uranium quantitatively and selectively from aqueous media at pH = 4 by using oleic acid as a surfactant. The different parameters affecting the flotation process have also been investigated. Uranium(VI) has been effectively separated from natural water samples and certified uranium ores using both procedures.     

EXTRACTION OF PLUTONIUM (III) BY TBP IN PRESENCE OF URANIUM

ABSTRACT

The distribution ratio (D) values for the extraction of plutonium (III) from nitric acid medium into 30% TBP in n-dodecane saturated with uranium(VI) (0% to 80%) were determined. For a fixed saturation of TBP with uranium, the D values for Pu(III) were found to increase with increase in nitric acid concentration (1M to 5M). At a fixed nitric acid concentration, the D values were found to decrease with increase in loading of TBP with uranium. The D values for the extraction of Pu(III) using 20% TBP in n-dodecane and 30% TBP in n-paraffin at 80% uranium saturation were also determined The distribution data was least squares analysed against concentration of HNO₃ as well as percentage saturation of TBP with uranium and the coefficients obtained are reported. For all these extraction systems, D values for U(VI) were also determined.     

Adsorption of Eu(III), Th(IV), and U(VI) by mesoporous solid materials bearing sulfonic acid and sulfamic acid functionalities

ABSTRACT

SBA-15 mesoporous materials modified by sulfonic acid and sulfamic acid functionalities, abbreviated as SBA-15/SO₃H and SBA-15/NHSO₃H, were synthesized and applied for the removal–separation of Eu(III), Th(IV), and U(VI). SBA-15/NHSO₃H showed an excellent selectivity toward U(VI), while SBA-15/SO₃H was more efficient adsorbent for Eu(III) and Th(IV). It was found that in the presence of KNO₃ (1 mol L^?1), the separation of Eu(III)/Th(IV) from their mixtures is possible. The results of the sorption behavior indicated a high adsorption capacity toward U(VI) and Th(IV) ions (140.5 and 106.7 mg g^?1, respectively) and ultrafast kinetics (15 min) in Eu(III) adsorption.     

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).     

Solvent Extraction of Plutonium(IV), Uranium(VI), and Some Fission Products with Di-n-octylsulfoxide

Abstract

Extraction behavior of plutonium(IV), uranium(VI), and some fission products from aqueous nitric acid media with di-n-octylsulfoxide (DOSO) has been studied over a wide range of conditions. Both the actinides are extracted essentially completely, whereas fission product contaminants like Zr, Ru, Ce, Eu, and Sr show negligible extraction. The absorption spectra of sulfoxide extracts containing either Pu⁴⁺ or UO₂ ²⁺ indicate the species extracted from nitric acid into the organic phase to be Pu(NO₃)₄. 2DOSO and UO₂(NO₃)₂. 2DOSO, respectively. Extraction of these actinides decreases with increasing temperature, indicating the extraction to be exothermic. DOSO extracts plutonium and uranium better than di-n-hexylsulfoxide (DHSO) under all condition and is also more soluble in aromatic diluents than the latter. The effect of gamma radiation on the extraction properties of DOSO is found to be similar to that of DHSO.     

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.     

Pseudo-Emulsion Based Hollow Fiber Strip Dispersion Technique (PEHFSD): Optimization,Modelling and Application of PEHFSD for Recovery of U(VI) from Process Effluent

Abstract

Pseudo emulsion based hollow fiber strip dispersion technique (PEHFSD) is the first of its kind ever explored in radioactive environment for the extraction of uranium from acidic process streams. Permeation of U(VI) was investigated as a function of various experimental variables such as hydrodynamic conditions (flow rates of pseudo-emulsion and feed phase), concentration of U(VI) in the feed phase, concentration of tri-n-butylphosphate (TBP), HNO₃ concentration in feed phase, O/A ratio and 0.01 M HNO₃ as stripping agent in pseudo-emulsion phase. The mass transfer coefficient was calculated from the experimental results and a model has been presented for determining mass transfer characteristics. PEHFSD has been demonstrated for separation/recovery of uranium from oxalate supernatant waste generated during plutonium precipitation by oxalic acid. PEHFSD and HFSLM (hollow fiber supported liquid membrane) performance has been compared in order to analyze the efficiency of the technique.     

Effect of an electric field on the transport of Th(IV) in the presence of Eu(III) and U(VI) through supported liquid membrane containing di‐2‐ethylhexylphosphoric acid

This paper investigates the transport of Th(IV) ions in nitric acid media through a supported liquid membrane (SLM) impregnated with di‐2‐ethylhexylphosphoric acid (HDEHP) in kerosene using an electric field. The transport was carried out in a three compartment cell fitted with microporous cellulose nitrate (SLM) and cation exchange membrane (Nafion). The effect of different parameters including nitric acid concentration in the feed solution, HDEHP concentration in the membrane, and HCl concentration were studied. The optimal conditions for Th(IV) transport were 0.1 mol dm^?3 HDEHP, 10^?3 mol dm^?3 HNO₃ in the feed solution, 1 mol dm^?3 HCl in compartment 2 and 1 mol dm^?3 HCl in compartment 3 at 25 °C. Under the optimal conditions of Th(IV) transport the recovery factor after 90 min was 0.25 without applying an electrostatic field, compared with 0.9 when the electric field was applied. The effect of electric current on the flux of Th(IV) through the membrane was also studied. The flux increased as the current density increased from 10 to 30 mA cm^?2 to reach a maximum value at 30 mA cm^?2 (8 × 10^?9 g eq cm^?2 s^?1). The transport percentages of 0.3 g dm^?3 Th(IV) in the presence of 0.1 g dm^?3 Eu(III) and 1 g dm^?3 U(VI) were 66, 84 and 15%, respectively. The determined selectivities of U(VI)–Th(IV) and Th(IV)–Eu(III) were 0.12 and 0.3, respectively, after 90 min. Therefore, the order of selectivity of this system is Eu(III) > Th(IV) > U(VI). © 2001 Society of Chemical Industry     

Extraction of Uranium(VI) and Thorium(IV) from Nitric Acid Solution by N,N,N′,N′ – Tetraoctylglutaricamide

Synthesis and characterization of N,N,N′,N′-tetraoctylglutaricamide (TOGA) was carried out and used for extraction of U(VI) and Th(IV) from nitric acid solutions. The processes of extraction were determined by the slope analysis and by analyzing a function that allows the simultaneous treatment of all the experimental points obtained in different conditions. The different factors affecting the extraction distribution ratio(D) of U(VI) and Th(IV) (extraction concentration, concentrations of nitric acid, salting-out agent NaNO₃ concentration, equilibration time, temperature, and types of diluents) were investigated. The results obtained indicated that the extraction species of U(VI) and Th(IV) are mainly extracted as UO₂(NO₃)₂·1.0TOGA and Th(NO₃)₄·1.5TOGA. The apparent equilibrium constant of U(VI) and Th(IV) extraction determined are 3.35 ± 0.03 L³/mol³ and 1.87 ± 0.01 L⁵/mol⁵ at 298 ± 1 K. Thermodynamic parameters such as the free energy(ΔG), enthalpy(ΔH), and entropy(ΔS) changes associated with the extraction processes could be evaluated. Back-extraction of U(VI) and Th(IV) from organic phases was also studied.     

Development of New Cationic Exchangers for the Recovery of Uranium (VI) from Concentrated Phosphoric Acid

The extraction of uranium (VI) from 5.3 mol.L^?1 phosphoric acid with a series of phosphoric, phosphinic, dithiophosphoric, or dithiophosphinic acid derivatives (0.5 mol.L^?1) in mixture with 0.125 mol.L^?1 TOPO in Isane IP 185 has been investigated. In the frame of the present work, eight acidic phosphorus and thiophosphorus compounds have been synthesized: bis(1,3-diisobutoxypropan-2-yl) phosphoric acid, bis(1,3-bis-(butylthio)propan-2-yl) phosphoric acid, bis(5,8,12,15-tetraoxanonadecan-10-yl) phosphoric acid, bis(1-butoxyheptan-2-yl) phosphoric acid, bis(undecan-6-yl) phosphoric acid, bis(2-(1,3-dibutoxypropan-2-yloxy)ethyl) phosphoric acid, bis(3-butoxy-2-(butoxymethyl)-2-methylpropyl) phosphinic acid, bis(1,3-dibutoxypropan-2-yl) dithiophosphoric acid. The properties of these molecules in mixtures with TOPO have been compared with those of other extractants such as bis(2-ethylhexyl) phosphoric acid, bis(2-ethylhexyl) dithiophosphoric acid, bis(2-ethylhexyl) phosphinic acid, Cyanex® 272, and Cyanex® 301. The replacement of phosphoric acid-type extractant by their phosphinic homologues dramatically decreases the affinity for uranium (VI) whereas the replacement of the phosphoric and phosphinic acid-type extractants by their dithio homologues affects positively the distribution coefficient of uranium (VI). It also appears that the steric hindrance effect is responsible for a significant decrease of the distribution coefficient of uranium (VI). Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science and Technology to view the free supplemental file.     

Uranium and Plutonium Extraction from Nitric Acid by N,N-Di(2-Ethylhexyl)-2,2-Dimethylpropanamide (DEHDMPA) and N,N-Di(2-Ethylhexyl)Butanamide (DEHBA) using Mixer-Settler Extractors

Extraction properties of N,N-di(2-ethylhexyl)-2,2-dimethylpropanamide (DEHDMPA) for nitric acid, U(VI), and Pu(IV) were studied by a batch method using various nitric acid concentrations. The distribution ratio equations for nitric acid, U(VI), and Pu(IV) were derived. A continuous counter-current experiment was performed using mixer-settler extractors to determine the performance of a process that uses two types of monoamides, DEHDMPA and N,N-di(2-ethylhexyl)butanamide (DEHBA), as extractants. This process consisted of two cycles: one dedicated to extraction of U(VI) by DEHDMPA, and the other dedicated to the co-extraction of U(VI) and Pu(IV) by DEHBA. The feed solution used for the continuous counter-current experiment was 4 mol/dm³ nitric acid containing U(VI), Pu(IV), and simulated fission products. DEHDMPA exclusively extracted U(VI) from the feed at the 1st cycle, and the ratio of U recovered in the U fraction stream was 99.93%. The residual U and almost all Pu were extracted by DEHBA in the 2nd cycle, and the recovery of Pu in the U-Pu fraction stream was 99.94%. Concentration profiles of U and Pu in mixer-settlers were calculated using a simulation code, which confirmed that the calculation was effective for estimating the U concentration in the U fraction stream, and the U and Pu concentrations in the U-Pu fraction stream.     

Note: Effect of Temperature in the Extraction of Uranium and Plutonium by Triisoamyl Phosphate

Abstract

The extraction of uranium(VI) by triisoamyl phosphate (TiAP) has been studied to derive the thermodynamic parameters such as entropy change and the free-energy change. The extraction of U(VI) and Pu(IV) has also been studied with 1.1 M solutions of tri-n-butyl phosphate (TBP), tri-n-amyl phosphate (TAP), and TiAP as a function of temperature. While the enthalpy of U(VI) extraction was found to be exothermic, the enthalpy for the extraction of Pu(IV) was always found to be endothermic. The temperature at which the distribution ratios of U(VI) and Pu(IV) cross each other (the temperature of inversion) has been derived for TBP, TAP, and TiAP, and the results reveal the lowest temperature of inversion occurs for TiAP. The results indicate the advantage of TiAP as an extractant in avoiding plutonium reflux during the PUREX process involving high plutonium feed solutions, in addition to lower aqueous solubility, freedom from the third-phase formation problem, lower degradation, and better economics.     

Solvent Extraction of Uranium (VI) from Chloride Solutions using Cyphos IL-101

The solvent extraction of uranium (VI) from chloride solutions by Cyphos IL-101 in xylene has been studied. Distribution coefficients were found to increase with aqueous chloride concentration and extractant concentration. The enthalpy of extraction is endothermic with ΔH = +24 ± 2 kJ·mol^?1. Based upon slope analysis, an anion exchange extraction mechanism is proposed, with formation of a UO₂Cl₄ ^2- complex in association with 4 Cyphos IL-101 ligands. The extraction kinetics were fast, with complete equilibration occurring within 30 seconds. An isotherm for uranium extraction from 1.0 mol·L^?1 chloride solution by 0.1 mol·L^?1 Cyphos IL-101 in xylene shows that 45 mmol·L^?1 uranium can be loaded into the organic phase in equilibrium with 2.1 mmol·L^?1 in the aqueous phase. The absorption spectrum of the uranium loaded solvent between 350 and 550 nm is indicative of the UO₂Cl₄ ^2- complex with only chlorides present in the inner coordination sphere, unlike the more strongly hydrogen bonded Alamine 336 extracted uranium complex. Subject to the same experimental conditions, distribution coefficients for Cyphos IL-101 were significantly greater than for Alamine 336 or Aliquat 336.     

Tuning the Extractive Properties of Purex Solvent using Room Temperature Ionic Liquid

An Aliquat-336 based ionic liquid, namely, tri-n-octylmethylammonium bis(2-ethylhexyl)phosphate ([A3636]⁺[DEHP]^?) was prepared and studied for the extraction of U(VI), Pu(IV), and Am(III) from nitric acid medium. Since the ionic liquid, [A336]⁺[DEHP]^? was miscible in n-dodecane (n-DD), the extraction of these actinides in the PUREX solvent, 1.1 M tri-n-butylphosphate (TBP) in n-dodecane (n-DD), was investigated in the presence of small concentrations of ionic liquid. The distribution ratio of U(VI) and Am(III) in 0.03 M [A336]⁺[DEHP]^?/n-DD decreased with increase in the concentration of nitric acid; whereas the extraction of Pu(IV) initially increased, it reached a maximum at 4 M nitric acid followed by the decrease. The extraction of actinides in ionic liquid medium decreased in the order Pu(IV) > U(VI) >> Am(III), indicating the feasibility of modifying the extractive properties of TBP/n-DD to favor Pu(IV) extraction. Therefore, the extraction of Pu(IV) in a solution of TBP – [A336]⁺[DEHP]^? in n-DD was also studied. The distribution ratio of Pu(IV) increased with increase in the concentration of ionic liquid and decrease in the concentration of TBP in organic phase. The distribution ratio of Pu(IV) determined in the presence of small concentration of ionic liquid in 1.1 M TBP/n-DD was always much higher than that observed in 1.1 M TBP/n-DD. In contrast to this, the distribution ratio of U(VI) decreased by the addition of ionic liquid and Am(III) was inextractable even in the presence of ionic liquid.     

Extraction of U(VI), Th(IV), and Lanthanides(III) from Nitric Acid Solutions with CMPO-Functionalized Ionic Liquid in Molecular Diluents

The extraction of microquantities of U(VI), Th(IV), and lanthanides(III) from nitric acid solutions with CMPO-functionalized ionic liquid 1-[3[[(diphenylphosphinyl)acetyl]amino]propyl]-3-tetradecyl-1H-imidazol-3-ium hexafluorophosphate, CMPO-FIL(I) in molecular organic diluents has been studied. The effect of HNO₃ concentration in the aqueous phase and that of extractant concentration in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes was determined. CMPO-FIL(I) demonstrates greater extraction ability towards Ln(III) than its neutral CMPO analog, diphenylphosphorylacetic acid N-nonylamide. This inner synergistic effect increases with a decreasing organic diluent polarity. The partition of CMPO-FIL(I) between the equilibrium organic and aqueous phases is the dominant factor governing the extractability of Ln(III) ions in the extraction system.     

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.