Tetraoctyl Diglycolamide Research Articles

Silver extraction by N,N,N′,N′-tetraoctyl-thiodiglycolamide

The novel tridentate extractant including a soft donor group or atom has developed and was examined. The extractant, N,N,N′,N′-tetraoctyl-thiodiglycolamide (TOTDGA), is analogous structure to N,N,N′,N′-tetraoctyl-diglycolamide (TODGA), but with sulfur donor instead of ether oxygen of TODGA. TOTDGA has a unique property to extract silver from acidic solutions to n-dodecane with relatively high D values. We investigated the extraction behavior of Ag in various acids, HNO3, H2SO4, and HClO4. The results suggest that TOTDGA can extract Ag from these acids.

Reprocessability of molybdenum and magnesia based inert matrix fuels

Abstract This work focuses on the reprocessability of metallic 92Mo and ceramic MgO, which is under investigation for (Pu,MA)-oxide (MA = minor actinide) fuel within a metallic 92Mo matrix (CERMET) and a ceramic MgO matrix (CERCER). Magnesium oxide and molybdenum reference samples have been fabricated by powder metallurgy. The dissolution of the matrices was studied as a function of HNO3 concentration (1-7 mol/L) and temperature (25-90°C). The rate of dissolution of magnesium oxide and metallic molybdenum increased with temperature. While the MgO rate was independent of the acid concentration (1-7 mol/L), the rate of dissolution of Mo increased with acid concentration. However, the dissolution of Mo at high temperatures and nitric acid concentrations was accompanied by precipitation of MoO3. The extraction of uranium, americium, and europium in the presence of macro amounts of Mo and Mg was studied by three different extraction agents: tri-n-butylphosphate (TBP), N,Nʹ-dimethyl-N,Nʹ-dioctylhexylethoxymalonamide (DMDOHEMA), and N,N,N’,N’- -tetraoctyldiglycolamide (TODGA). With TBP no extraction of Mo and Mg occurred. Both matrix materials are partly extracted by DMDOHEMA. Magnesium is not extracted by TODGA (D < 0.1), but a weak extraction of Mo is observed at low Mo concentration.

Solvent extraction behavior of trivalent metal ions in diglycolamides having same carbon to oxygen ratio

Various diglycolamides (DGAs), N,N,N’,N’-tetraoctyl diglycolamide (TODGA), N,N-di-2-ethylhexyl-N’,N’-di-octyl diglycolamide (DEHDODGA), N,N,N’,N’-tetra-2-ethylhexyl diglycolamide (TEHDGA), N,N-di-decyl-N’,N’-di-hexyl diglycolamide (D2DHDGA), N,N-di-butyl-N’,N’-di-dodecyl diglycolamide (DBD3DGA), N,N,N’,N’-tetra-hexyl diglycolamide (THDGA), and N,N,N’,N’-tetradecyl diglycolamide (TDDGA) have been synthesized and studied for the extraction of Am(III) and Eu(III) from nitric acid medium. An attempt was made to understand the extraction and third phase formation behavior of trivalent metal ions in these DGAs. Our results revealed that despite having the same carbon to oxygen ratio in these DGAs, the third phase formation behavior and extractions achieved in these DGAs are significantly different.

Sorption of REE(III), Th(IV), and U(VI) ions from nitric acid solutions with sorbents based on tetraoctyldiglycolamide

The characteristics of various sorbents based on tetraoctyldiglycolamide (TODGA) in sorption of REE(III), Th(IV), and U(VI) ions from nitric acid solutions were studied. The static capacity of the sorbents increases as the TODGA content of the sorbent and HNO3 concentration in the initial solution are increased. Europium can be desorbed with dilute HNO3 (0.01 M) and complexone (DTPA) solutions. The sorption characteristics of the sorbents in repeated sorption–desorption cycles remain stable. The sorbents prepared by joint copolymerization (solid extactants, SEs) exhibit better sorption and kinetic characteristics compared to the sorbents prepared by impregnation of the ready polymeric matrix.

Evaluation of hydrodynamic suitability of N,N-didodecyl N′,N′-di-octyl diglycolamide: a potential candidate for minor actinide partitioning

An unsymmetrical diglycolamide namely N,N, didodecyl-N′,N′-dioctyl diglycolamide developed in our laboratory is evaluated for its hydrodynamic suitability by determining the changes in its physical properties such as density and viscosity as a function of temperature and compared with those of tri n-butyl phosphate and N,N,N′,N′-tetraoctyl diglycolamide. The effect of irradiation on density, viscosity and interfacial tension, up to a dose of 1000 kGy are also measured. In addition, the activation energy for the viscous flow (E vis) were obtained for these pure solvents and their binary mixtures with n-dodecane in the temperature range 20–65 °C using the Andrade’s equation.

Extraction of U(VI) with N,N,N′,N′-tetraoctyl diglycolamide from nitric acid solution

The extraction of U(VI) from nitric acid solution with N,N,N′,N′-tetraoctyl diglycolamide (TODGA) has been investigated. The influence of diluents, nitric acid concentrations, TODGA concentration and salting-out agents on the extraction distribution ratio was studied. The extraction mechanism was established and the stoichiometry of the main extracted species was confirmed to be UO2(NO3)2·2TODGA. The extraction of UO22+ varies with the nature of diluents, sulfonated kerosene and dodecane gave high extraction distribution ratio.

Density functional theoretical analysis of structure, bonding, interaction and thermodynamic selectivity of hexavalent uranium (UO2 2+) and tetravalent plutonium (Pu4+) ion complexes of tetramethyl diglycolamide (TMDGA)

In the well-known PUREX process, tertiary butyl phosphate shows preferential extraction of UO2 2+ over Pu4+, whereas tetraoctyl diglycolamide (TODGA) displays the reverse selectivity. The reversal of selectivity toward diglycolamide has been investigated here theoretically by considering shorter analogue of TODGA, tetramethyl diglycolamide (TMDGA). Structure, bonding, energetic parameter and thermodynamic parameters of UO2 2+ and Pu4+ ions with TMDGA in the gas and solvent phase have been reported in order to understand their complexation and extraction behavior. The calculation has been performed with generalized gradient approximated BP86 density functional and hybrid B3LYP functional employing SVP and TZVP basis set. The calculated structure obtained at BP86/SVP level of optimization is found to be in close agreement with the reported experimental data. The free energy of extraction, ΔG ext, of UO2 2+ and Pu4+ ions from aqueous phase to the dodecane phase has been computed using the Born-Haber thermodynamic cycle in conjunction with COSMO (conductor like screening model) solvation approach. The free energy of extraction is predicted to be exergonic for explicit monomer water model. The free energy of extraction for Pu4+ ion is shown to be higher than that of UO2 2+ as observed in the reported solvent extraction experiment. Further, the suitability of non-polar solvents as organic diluents has been confirmed by the decreased free energy of extraction with increasing dielectric constant of the solvents. Natural population and orbital analysis indicate the electrostatic and small covalent nature of interactions between the metal ions and the tridentate TMDGA chelating ligand. The results presented here might be helpful in designing new ligands for efficient extraction of actinides.

Supercritical Fluid Dissolution and Extraction of Trivalent Metal Cations from Different Matrices

Studies on the recovery of trivalent metal ions such as Nd3+Eu3+ (taken as homologs of Am(III)) from solid oxide (Nd2O3), Thorium concentrate (obtained from Monazite ore processing), tissue paper/surgical gloves (rubber), and plant samples have been carried out by supercritical fluid extraction (SFE) using supercritical CO2 and ethanol/nitric acid. N,N,N’,N’-tetraoctyl diglycolamide (TODGA) was used as the extractant in these studies. The results showed that the recovery of Nd increased with TODGA concentration from 50% (no TODGA) to 70% (10% TODGA) at 3 M HNO3 in ethanol. However, the extraction of Nd at 1 M HNO3 was invariant with 1-3% (v/v) TODGA concentration (73 ± 4%). Interestingly, REEs recovery from Th concentrate was ˜ 60% even without TODGA using ethanol/3 M HNO3 mixture. On the other hand, quantitative recovery of 152,154Eu from tissue paper and surgical gloves sample could be achieved using 3 M HNO3/ethanol mixture. This suggested that it would be possible to decontaminate the contaminated laboratory waste papers using SFE technique.

A novel sorbent for lanthanide adsorption based on tetraoctyldiglycolamide, modified carbon inverse opals

Carbon inverse opals (C-IOP) were noncovalently modified with tetraoctyldiglycolamide (TODGA).

Extracted species of Np(IV) complex with diglycolamide functionalized task specific ionic liquid: diffusion, kinetics and thermodynamics by cyclic voltammetry

This paper reports a first-ever cyclic voltammetric study and the electrochemical characterization of Np(IV) complexes with task-specific ionic liquid with appended diglycolamide (DGA-TSIL) ligand dissolved in the room-temperature ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C4mimNTf2). The results are compared with molecular entity, N,N,N′,N′-tetraoctyl diglycolamide (TODGA) dissolved in the same diluent. The diffusion coefficient (D) values were determined using the Randles–Sevcik equation. The standard rate constant (k s) values were also computed for the Np(IV)/Np(III) electrode redox reaction. The activation energy for diffusion (E a) and thermodynamic parameters for the redox reactions of the Np complexes were determined and compared.

Effect of irradiation on some actinide and fission product ions' extraction using several tetraalkyl diglycolamides

Abstract The radiolytic stability of different substituted diglycolamides such as N,N,N′,N′-tetrapentyl diglycolamides(TPDGA), N,N,N′,N′-tetrahexyl diglycolamide (THDGA), N,N,N′,N′-tetraoctyl diglycolamide (TODGA), N,N,N′,N′-tetradecyl diglycolamide (TDDGA) and N,N,N′,N′-tetra-2-ethyl hexyl diglycolamide (T2EHDGA) was investigated in solvent systems containing 30% iso-decanol as a phase modifier in n-dodecane kept in contact with a 3 M HNO3 aqueous solution while irradiating in a gamma ray chamber up to 1000 kGy. The degradation of the solvent systems was qualitatively ascertained from measuring the distribution ratio values at 3 M and 0.2 M HNO3 which gave a direct indication of the reusability of the solvent for long term reuse in separation processes such as `actinide partitioning'. The effect of irradiation on distribution values of Sr, Pu, U was also investigated with diglycolamide extractants both under extraction and stripping conditions. Stoichiometry of the extracted species was determined for Am(III) extraction using the fresh as well as the irradiated solvent systems involving all the five substituted diglycolamides at 3 M HNO3 and the results indicated only marginal changes. GC-MS analysis was done for fresh and irradiated solvent systems of all the diglycolamides and attempts were made to identify the degradation products.

Spectacular enhancements in actinide ion uptake using novel extraction chromatography resins containing TODGA and ionic liquid

Several novel extraction chromatographic (XC) resins were prepared with varying compositions of N,N,N′,N′-tetraoctyl diglycolamide (TODGA) and [C4mim][NTF2] (a room temperature ionic liquid) impregnated onto Chromosorb-W. The first set of XC resins had varying fractions of TODGA (10–30% (w/w)) with a fixed amount (10% (w/w)) of the room temperature ionic liquid (RTIL), while the RTIL composition was varied (10–30% (w/w)) for the second set of resins while keeping a fixed (10% (w/w)) amount of TODGA. In the third set of resins, both TODGA as well as RTIL contents were varied in the range10–30% (w/w). The loading of Eu(III) on the resin increased linearly from 8.74±0.40mg/g to 23.66±0.17mg/g with increasing TODGA concentration from 10% TODGA to 30%. However, increase in the RTIL concentration did not affect the Eu loading. The loading of Eu(III) deviated from the stoichiometric value of 1:3 (metal:ligand) with increased TODGA concentration.Sorption isotherms were obtained for Eu(III) and the data were fitted with models such as Langmuir, Freundlich and Dubinin–Radushkevich (D–R). The results suggested that the sorption of Eu(III) on TODGA-RTIL resin followed the Langmuir mono layer chemisorptions model with sorption energy (obtained from the D–R model fitting) of 21.28±1.27kJ/mol. The results of the column studies revealed that 6.67mg Eu could be loaded per gm of resin on the column without any breakthrough. The loaded Eu from the column was efficiently eluted in about 5mL of 0.01M EDTA solution. Distribution coefficient measurements of various metal ions suggested selective sorption of trivalent f-elements over hexavalent uranyl ions and other fission product elements over a wide range of acidity (0.01–6M HNO3).

Water Soluble PDCA Derivatives for Selective Ln(III)/An(III) and Am(III)/Cm(III) Separation

The synthesis and solvent extraction behavior of dipicolinic acid (pyridine-2,6-dicarboxylic acid, PDCA) and their derivatives have been studied for possible use in selective back-extraction of actinides, especially americium. The extraction was performed from an organic phase containing a mixture of trivalent actinides and lanthanides pre-extracted with N,N,N’,N’-tetraoctyl diglycolamide (TODGA). The efficiency of the back-extraction was enhanced when the picolinate platform was used in a heterocyclic decadentate ligand called h4tpaen. Beyond selective An/Ln extraction, the aqueous soluble h4tpaen ligand seemed a potential reagent for an intra-group Am(III)/Cm(III) separation with a separation factor SFCm/Am of about 3.5.

Laboratory-Scale Counter-Current Centrifugal Contactor Demonstration of an Innovative-SANEX Process Using a Water Soluble BTP

In this paper the development and laboratory-scale demonstration of a novel “innovative-SANEX” (Selective Actinide Extraction) process using annular centrifugal contactors is presented. In this strategy, a solvent comprising the N,N,N’,N’-tetraoctyldiglycolamide (TODGA) extractant with addition of 5 vol.-% 1-octanol showed very good extraction efficiency of Am(III) and Cm(III) together with the trivalent lanthanides (Ln(III)) from simulated Plutonium Uranium Refining by Extraction (PUREX) raffinate solution without 3rd phase formation. Cyclohexanediaminetetraacetic acid (CDTA) was used as masking agent to prevent the co-extraction of Zr and Pd. An(III) and Ln(III) were co-extracted from simulated PUREX raffinate, and the loaded solvent was subjected to several stripping steps. The An(III) were selectively stripped using the hydrophilic complexing agent SO3-Ph-BTP (2,6-bis(5,6-di(sulfophenyl)-1,2,4-triazin-3-yl)pyridine). For the subsequent stripping of the Ln(III), a citric acid based solution was used. A 32-stage process flow-sheet was designed using computer-code calculations and tested in annular miniature centrifugal contactors in counter-current mode. The innovative SANEX process showed excellent performance for the recovery of An(III) from simulated High Active Raffinate (HAR) solution and separation from the fission and activation products. ≥ 99.8% An(III) were recovered with only low impurities (0.4% Ru, 0.3% Sr, 0.1% Ln(III)). The separation from the Ln(III) was excellent and the Ln(III) were efficiently stripped by the citrate-based stripping solution. The only major contaminant in the spent solvent was Ru, with 14.7% of the initial amount being found in the spent solvent. Solvent cleaning and recycling therefore has to be further investigated. This successful spiked test demonstrated the possibility of separating An(III) directly from HAR solution in a single cycle which is a great improvement over the former multi-cycle strategy. The results of this test are presented and discussed.

Synergistic Extraction of Lanthanides in a Liquid-Liquid Countercurrent Centrifugal Extractor

We have developed a liquid-liquid countercurrent centrifugal extractor that induces Taylor vortices in the annular fluid region. To demonstrate extraction of multiple species (Nd/Sm/Eu/Gd/Dy) with N,N,N′,N′-tetraoctyl diglycolamide (TODGA), additional chemical agents, such as a surfactant (sodium bis(2-ethylhexyl) sulfosuccinate (AOT)), a synergist (nonanoic acid) and a masking agent (N,N,N′,N′-tetraethyl-3,6-dioxaoctane-1,8-diamide (DOODA(C2))) were employed. When only TODGA was utilized, extraction performance was not effective due to the insufficient dispersion even under a high rotating speed. By combining TODGA and other chemical agents, the separation performance was improved considerably in the countercurrent flow of aqueous and organic phases due to the synergistic effect and improved dispersion.

Diglycolamide-functionalized task specific ionic liquids for nuclear waste remediation: extraction, luminescence, theoretical and EPR investigations

A 3.6 × 10−2 M solution of a diglycolamide-functionalized task specific ionic liquid (DGA-TSIL) in [C4mim][NTf2] was used for the extraction of actinides (mainly Am) and other elements present in high level nuclear waste. The extraction of Eu3+ was relatively higher than that of Am3+ conforming to the mechanism displayed by other diglycolamide extractants such as TODGA (tetraoctyl diglycolamide). The distribution ratio values decreased in the presence of simulated high level waste (SHLW) as compared to those obtained with pure tracers. The nature of the extracted species was established by the slope analysis method which suggested 1 : 2 species for the extraction of Am3+ and Eu3+. Calculation of the Judd–Ofelt parameters from the luminescence data of the Eu3+ complexes indicated that the structure of the extracted complexes exhibits S4 symmetry. Theoretical calculations showed virtually no difference between the structures of the complexes of Am3+ and Eu3+. The nature of the radiolytic degradation products was analyzed by electron paramagnetic resonance (EPR) spectroscopic measurements revealing the presence of alkyl imidazolium and methyl radicals.

Non-Dispersive Solvent Extraction of Neodymium using N,N,N’,N’-Tetraoctyl Diglycolamide (TODGA)

Hollow fiber contactor was used to study non-dispersive extraction (NDSX) of Nd3+ ions from aqueous solutions. N,N,N′,N′-tetraoctyl diglycolamide (TODGA) diluted with n-dodecane was used as the organic phase with di-n-hexyl octanamide (DHOA) as the phase modifier. The role of cations (H+/Na+) on the transport of Nd3+ ions has been investigated for this system. It was observed that H+ ion has a significant role to play in the Nd3+/TODGA complexation reaction. A mathematical model has also been developed to simulate the NDSX process in a hollow fiber contactor. A comparison has also been made between extraction profiles from the NDSX process and the hollow fiber supported liquid membrane (HFSLM) process. It was observed that NDSX gave comparatively faster rates of extraction in the presence of H+ ions but slower in the absence of H+ ions.

Simultaneous Extraction of Neodymium and Uranium using Hollow Fiber Supported Liquid Membrane

Simultaneous extraction of neodymium and uranium ions from aqueous nitrate media was investigated using hollow fiber supported liquid membrane (HFSLM). The organic phase supported in the membrane pores consisted of extractant N,N,N’,N’-tetraoctyl diglycolamide (TODGA), phase modifier isodecanol, and diluent n-dodecane. Experimental results suggest that there is competition between neodymium and uranium ions for complexation with TODGA. The initial rate of extraction of Nd3+ ions was found to be approximately six times to that of UO22+ ions. Experimental data was explained by a mathematical model for simultaneous transport of two metal ions. The model results were found to be in good agreement with the experimental data when the diffusivities of neodymium-TODGA complex (Dnm) and uranium-TODGA complex (Dum) in the membrane pore are 1.1 x 10−11 and 4 x 10−12 m2/s, respectively.

Development of a New Flowsheet for Co-Separating the Transuranic Actinides: The “EURO-GANEX” Process

A flowsheet for a novel GANEX (Grouped ActiNide EXtraction) process has been tested in a spiked flowsheet trial in a 32 stage plutonium-active centrifugal contactor rig with a simulant feed that contained 10 g/L plutonium as well as some fission products and other transuranic actinides. The solvent system used was a combination of 0.2 mol/L N,N,N’,N’-tetraoctyl diglycolamide (TODGA) and 0.5 mol/L N,N’-(dimethyl-N,N’-dioctylhexylethoxy-malonamide (DMDOHEMA) in a kerosene diluent that co-extracted actinides and lanthanides. Actinides were subsequently selectively co-stripped away from the lanthanides using a sulphonated and, therefore, hydrophilic bis-triazinyl pyridine (BTP) complexant in conjunction with acetohydroxamic acid (AHA). Plutonium and americium recoveries were high with decontamination factors across the strip contactors of ˜14,000 and ˜390, respectively. However, approximately 30% of neptunium was lost to the aqueous raffinate which was due to recycling within the first extract-scrub section causing a large build-up of neptunium. Some accumulation of strontium was also observed but in this case it was fully directed to the raffinate stream. In the stripping section, a small fraction of europium (taken as a model lanthanide ion), ca. 7%, was found in the actinide product stream. Modelling of selected data using the PAREX code has shown that even with a relatively simplistic treatment, reasonable agreement between modelling and experiment can be obtained, giving confidence in the use of modelling to refine the GANEX flowsheet design prior to further testing with irradiated fast reactor fuel.

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.