Tetraoctyl Diglycolamide Research Articles

Evaluation of selected solvent systems for the single-cycle separation of Am(III) from Eu(III) using aqueous soluble sulphonated bis-triazinylpyridine

Abstract The process methods developed for partitioning of trivalent actinides from high-level liquid waste (HLLW) are being focussed on single-cycle processing approaches. This method involves the separation of trivalent actinides and chemically similar lanthanides, as a group, from HLLW followed by the mutual separation of lanthanides and actinides from the loaded organic phase using aqueous soluble complexing agents. The potential solvents identified for the group separation of trivalents from HLLW are 1) 0.2 M TODGA (N,N,N’N′-tetraoctyldiglycolamide) + 5% octanol / n-DD, 2) 0.2 M TODGA + 0.5 M TBP (tri-n-butylphosphate) / n-DD, 3) 0.1 M TODGA + 0.25 M HDEHP (di-(2-ethylhexyl)phosphoric acid) / n-DD, 4) 0.2 M TDDGA (N,N,N’N′-tetradecyldiglycolamide) / n-DD, 5) 0.2 M D3DODGA (N,N-didodecyl-N’N′-dioctyldiglycolamide) / n-DD, 6) 0.4 M DOHyA (N,N-dioctyl-2-hydroxyacetamide) / n-DD. The extraction behaviour of Am(III) and Eu(III) from dilute nitric acid solution (0.1 M to 1 M) containing aqueous soluble nitrogen-donor derivative, SO3-Ph-BTP, was studied in the above solvents. The separation factor (SF) of Eu(III) over Am(III) was determined. Among the different solvents investigated, the SF achieved in TDDGA and D3DODGA was quite higher than other solvents, and recommended for the single-cycle separation of trivalent actinides from HLLW.

Gamma Radiolysis of TODGA and CyMe4BTPhen in the Ionic Liquid Tri-n-Octylmethylammonium Nitrate

ABSTRACTRadiolytic stability of the extractants N,N,N’,N’-tetraoctyl diglycolamide (TODGA) and 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline (CyMe4BTPhen) in the ionic liquid tri-n-octylmethylammonium nitrate ([N1888][NO3]) was studied via the combination of a steady-state irradiation by cobalt-60 gamma-radiation, followed by solvent extraction and identification of radiolysis products by High-Performance Liquid Chromatography coupled to Electro Spray Ionisation Mass Spectrometry (HPLC-ESI-MS). The observed trend for the distribution ratios of trivalent minor actinides and Eu(III) showed a decrease as a function of absorbed dose in the case of the TODGA solvent. The gamma irradiations were conducted in the presence or absence of an acidic aqueous phase. The determined dose constants for TODGA under neutral or acidic conditions were up to four times lower than the values reported in aliphatic diluents under comparable conditions. The degradation patterns were similar to those found by former studies on TODGA diluted in n-dodecane; only de-alkylation and bond ruptures within the diglycolamide core were observed. The presence of an acidic aqueous phase during irradiation resulted in a different relative abundance of certain radiolysis products of both the diluent and TODGA and a higher dose constant compared to the neutral irradiation conditions. A quantification of CyMe4BTPhen in irradiated samples with the [N1888][NO3] diluent was not possible, but the effect on its extraction properties was evaluated. The distribution ratios slightly increased under the effect of absorbed dose, indicating the formation of radiolysis products that are efficient extractants as well.

Interference of Zr(IV) during the extraction of trivalent Nd(III) from the aqueous waste generated from metallic fuel reprocessing

Abstract A metallic alloy of uranium–zirconium and uranium–plutonium–zirconium has been proposed as a fuel for fast reactors, owing to the possibility of achieving high breeding ratio in a short span of time. About 6–10 wt.% of zirconium has been added to these actinide fuels to increase the melting temperature and thermal-mechanical stability. Aqueous reprocessing of the spent metallic fuel generates the high-level liquid waste (HLLW) that contains about 60 % of the total zirconium from the fuel. In view of this, the extraction behavior of a trivalent representative ion, Nd(III) in the presence of Zr(IV) was studied from nitric acid medium using the candidate ligands proposed for trivalent actinide separation from HLLW, such as N,N,N′N′-tetraoctyldiglycolamide (TODGA), and N,N-di-octyl-2-hydroxyacetamide (DOHyA). The extraction was studied as a function of nitric acid concentration, zirconium and neodymium concentration and Nd(III) to Zr(IV) ratio. The findings of dynamic light scattering (DLS) and ATR-FTIR spectral techniques were used for understanding the complex chemistry of Zr(IV) extraction under different conditions. Poor extraction of nitric acid, smaller aggregate size, no third phase formation during the extraction of Zr(IV) and Nd(III) and other unique solvent properties favor the DOHyA molecule in n-dodecane as a solvent for partitioning of trivalent actinides from HLLW generated from metallic fuel reprocessing.

Sorption properties of polymeric beads and films containing tetraoctyl diglycolamide towards europium (III) ions

The article presents results obtained during investigation of Eu(III) ion removal from aqueous solutions using triacetate cellulose films and styrene-divinylbenzene copolymer beads containing tetraoctyl diglycolamide (TODGA). A simple method for manufacturing films containing up to 50 % w/w TODGA is provided. Solution acidity effect on the removal rate of Eu(III) ions was studied. Maximum removal of Eu(III) ions was obtained in nitric acid solutions with concentrations of 1-6 mol/l. Additionally, increase in the europium removal rate is also observed at pH > 2 for beads and in the pH range of 2 to 4 for films. In the former case increase in the removal rate is explained by increase in the nitrate ion concentration in the solution and Eu(NO3)3(TODGA)3 complex formation, and in the latter case – by decrease in TODGA protonation rate with рН growth. Observed trends indicate a high similarity in surface sorption mechanisms between the materials studied. Sorption equilibrium of Eu(III) ions onto the styrene-divinylbenzene copolymer beads impregnated with TODGA is adequately fitted to Langmuir sorption isotherm. The maximum sorption capacity of this material for Eu(III) removal from solutions with nitric acid concentration of 1 mol/l is 7.4 mg/g. It has been found that the maximum removal rate of Eu(III) ions by the triacetate cellulose films is achieved for TODGA content in the films ≥ 40 % w/w. The possibility of selective europium sorption from natural water using both beads and films is shown. Although cations present in natural water do not bind to sorbents studied, there is still slight deterioration in sorption properties when moving from model solutions to natural water. Complete desorption of Eu(III) ions from the film surface is achieved by washing three times with an EDTA solution, рН = 6.8. Prepared films can be reused for Eu(III) ion removal.

Does addition of 1-octanol as a phase modifier provide radical scavenging radioprotection for N,N,N',N'-tetraoctyldiglycolamide (TODGA)?

To mitigate third phase formation in next generation used nuclear fuel reprocessing technologies, the addition of 1-octanol has been trialed. However, contradictory reports on the radiolytic effect of 1-octanol incorporation on separation ligand degradation need to be resolved. Here, 50 mM N,N,N',N'-tetraoctyldiglycolamide (TODGA) dissolved in n-dodecane was gamma irradiated in the presence and absence of 1-octanol (2.5-10 vol%) and a 3.0 M HNO3 aqueous phase. Radiation-induced TODGA degradation exhibited pseudo-first-order decay kinetics as a function of absorbed gamma dose for all investigated solution and solvent system formulations. The addition of 1-octanol afforded diametrically different effects on the rate of TODGA degradation depending on solvent system formulation. For organic-only irradiations, 1-octanol promoted TODGA degradation (d = 0.0057 kGy-1 for zero 1-octanol present vs.∼0.0073 kGy-1 for 7.5-10 vol%) attributed to a favourable hydrogen atom abstraction reaction free energy (-0.31 eV) and the ability of 1-octanol to access a higher yield of n-dodecane radical cation (RH˙+) at sub-nanosecond timescales. This was rationalized by determination of the rate coefficient (k) for the reaction of 1-octanol with RH˙+, k = (1.23 ± 0.07) × 1010 M-1 s-1. In contrast, irradiation in the presence of 1-octanol and a 3.0 M HNO3 aqueous phase afforded significant radioprotection (d = 0.0054 kGy-1 for zero 1-octanol present vs.≤ 0.0044 kGy-1 for >2.5 vol%) that increases with 1-octanol concentration, relative to the single phase, organic-only solutions. This effect was attributed to the extraction of sufficiently high concentrations of HNO3 and H2O into the organic phase by TODGA and 1-octanol as adducts which interfere with the hydrogen atom abstraction process between the 1-octanol radical and TODGA. Our findings suggest that the addition of 1-octanol as a phase modifier will enhance the radiation robustness of TODGA-based separation technologies under envisioned solvent system conditions in the presence of aqueous HNO3.

Recovery of rare earths from phosphate ores through supported liquid membrane using N,N,N′,N′-tetraoctyl diglycol amide

The rare earth elements (REEs) such as lanthanum, cerium, praseodymium, and neodymium were successfully recovered from the leaching solutions of phosphate ores through a Supported Liquid Membrane (SLM). The extractant, N,N,N′,N′-tetraoctyl diglycol amide (TODGA), was employed as novel carrier for REEs transport. Permeation rate was observed to be significantly fast and more than 95.0% of REE3+ was collected using 0.10 M TODGA as carrier. The mechanism of transport was investigated by studying various parameters, such as feed HNO3 and NaNO3 concentration, TODGA concentration in the membrane and the stirring rate etc. In view of practical application to the collection of REEs from the phosphate ore leaching liquor, the stability of the membrane was also studied. The result shows that the membrane was highly selective for lanthanides. This research would provide a new environmentally friendly and new sustainable green approach for the recovery of REE with SLM technique.

FTIR Spectra of N,N,N',N'-Tetraoctyl Diglycolamide Complex in Room Temperature Ionic Liquids

The interaction of an octyl derivative of diglycolamide extractant complex in three different types of room temperature ionic liquids (RTILs) was studied by ATR-FTIR spectroscopic method. The shift in stretching vibrational frequencies for the functional groups (C=O and C-O) in the nitrate ion-extractant complexes and metal ion-extractant complexes in room temperature ionic liquids namely, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTf2], 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([C4mpyr][NTf2]) and 1-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide ([C4mpip][NTf2]) was compared. These results were also compared with that obtained for molecular diluent system, n-dodecane.

Unprecedented Inversion of Selectivity and Extraordinary Difference in the Complexation of Trivalent f Elements by Diastereomers of a Methylated Diglycolamide.

When considering f elements, solvent extraction is primarily used for the removal of lanthanides from ore and their recycling, as well as for the separation of actinides from used nuclear fuel. Understanding the complexation mechanism of metal ions with organic extractants, particularly the influence of their molecular structure on complex formation is of fundamental importance. Herein, we report an extraordinary (up to two orders of magnitude) change in the extraction efficiency of f elements with two diastereomers of dimethyl tetraoctyl diglycolamide (Me2 -TODGA), which only differ in the orientation of a single methyl group. Solvent extraction techniques, extended X-ray absorption fine structure (EXAFS) measurements, and density functional theory (DFT) based ab initio calculations were used to understand their complex structures and to explain their complexation mechanism. We show that the huge differences observed in extraction selectivity results from a small change in the complexation of nitrate counter-ions caused by the different orientation of one methyl group in the backbone of the extractant. The obtained results give a significant new insight into metal-ligand complexation mechanisms, which will promote the development of more efficient separation techniques.

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

ABSTRACTSolvents 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.

Determination of trace rare earth elements in fruits by microwave digestion coupled with inductively coupled plasma optical emission spectrometry

In this work, a novel method was developed for the determination of trace rare earth elements (REEs) in fruit samples by microwave digestion coupled with inductively coupled plasma optical emission spectrometry (ICP-OES) after preconcentration with N, N, N′, N′-tetraoctyl diglycolamide (TODGA). The parameters affecting the extraction and back-extraction behaviors of the target analytes in liquid-liquid extraction (LLE) were studied systematically. Under the optimum conditions, the limits of detection (3σ, n = 7) for the target REEs of interest were in the range of 0.0548 (Tb)–0.541 (La) μg L−1, and the tolerable concentration ratios were reaches 4 orders of magnitude for the common interfering ions. The relative standard deviations (c = 100 μg L−1, n = 7) were from 0.6% (Sm) to 3.3% (La) with the wide linear range spanned three orders of magnitude (R2 > 0.999). The recoveries for the spiked fruit samples were ranged from 92.1% to 104%. The proposed method has the advantages of simple operation, good anti-interference ability, simultaneous determine 16 REEs, which has been successfully applied for analysis of REEs in the 10 locally collected fruit samples, thereby exhibits application potential for the analysis of trace REEs in biological samples with complex matrix.

Highly efficient separation of Am3+ and Eu3+ using an aqueous soluble sulfonated BTP derivative by hollow-fiber supported liquid membrane containing TODGA

ABSTRACTSeparation of Am3+ and Eu3+ was attempted using phenyl sulphonic acid functionalized bis-triazinyl pyridine (SO3-Ph-BTP) employing supported liquid membrane-based technique with varying concentrations of N,N,N’,N’-tetraoctyl diglycolamide as the liquid membrane. Supported liquid membrane-based separation of Am3+ and Eu3+ was attempted for the first time using a hollow-fiber contactor. A single-fiber-based hollow-fiber microextraction could selectively concentrate Am3+ with a volume reduction factor of >1000. On the other hand, Eu3+ was selectively transported from a mixture of Am3+ and Eu3+ from 100 ml feed solution containing SO3-Ph-BTP in 30 min with a DF >100.

A Simplified Method Using a Single N,N,N',N'-Tetraoctyl Diglycolamide Resin Column for the Purification of Sr, Nd and Hf in Geological Materials and the Determination of Their Isotopic Ratios by Multi-collector Inductively Coupled Plasma-Mass Spectrometry.

A simplified method using a single column of N,N,N',N'-tetraoctyl diglycolamide (TODGA) resin is developed for the separation of Sr, Nd and Hf with matrix and interference elements from geological samples, and for subsequent determination of their isotopic ratios by multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). The analytes of Sr, Nd and Hf are absorbed by the TODGA resin and eluted with 6 mol/L HNO3, 1.2 mol/L HCl and 1 mol/L HNO3-1.6 mol/L HF, respectively. The separation procedure is validated by the certified reference materials (CRMs) of BHVO-2, BCR-2 and AGV-2 with analyte recovery greater than 97%. The ratios are measured for 87Sr/86Sr, 143Nd/144Nd and 176Hf/177Hf and the mean values (2σ) are 0.703455 (16), 0.512977 (12) and 0.283108 (8) for BHVO-2, 0.705008 (18), 0.512633 (10) and 0.282878 (4) for BCR-2, and 0.703989 (20), 0.512791 (8) and 0.282982 (8) for AGV-2, which are consistent with the certified values.

A study of cerium extraction kinetics by TODGA in acidified and non-acidified organic solvent phases in the context of fission product management

In the context of management of the waste streams arising from the reprocessing of spent nuclear fuel, studies have been conducted into the solvent extraction kinetics of lanthanide fission products by the oxygen-donor ligand N,N,N’,N’-tetraoctyl diglycolamide (TODGA) and the effects of solvent phase acidity on the effectiveness of this organic extractant molecule. In this study, we observe a reduction in the rate of cerium extraction as solvent phase acidity increases, attributed to aggregation of the extractant. The effect is shown to be reversible through neutralization while a permanent prevention method is the subject of further work.

Recovery of rare earths from nitric acid leach solutions of phosphate ores using solvent extraction with a new amide extractant (TODGA)

The rare earths in phosphate ores are not effectively utilized and they cannot be directly extracted from leach liquor with the traditional extractants, such as organic phosphoric acid. This paper presents a new solvent extraction method for rare earths from nitric acid leaching of phosphate rock using N,N,N′,N′-tetraoctyl diglycol amide (TODGA) without interfering with the normal route for fertilizer production. When the concentration of extractant increased to 0.1 mol/L, the extraction rate of lanthanum, cerium, praseodymium, and neodymium have been found to be 98.1%, 99.1%, 98.8% and 98.6%, respectively. The recovery rate reached to 99.9% when a three-stage countercurrent extraction was carried out on the simulated leach solution. There was almost no extraction of other impurity ions and the rare earths could be separated with TODGA from Ca2+, PO43−, Fe3+, and Mg2+. The presence of phosphoric acid in solution enhanced the extraction of rare earth ions. The stripping of the loaded rare earth in the organic phase was readily carried out with water under room temperature with high efficiency. The mixed rare earth oxides (REO) with an assay of >95% could be recovered as a final product.

Outer-Sphere Water Clusters Tune the Lanthanide Selectivity of Diglycolamides.

Fundamental understanding of the selective recognition and separation of f-block metal ions by chelating agents is of crucial importance for advancing sustainable energy systems. Current investigations in this area are mostly focused on the study of inner-sphere interactions between metal ions and donor groups of ligands, while the effects on the selectivity resulting from molecular interactions in the outer-sphere region have been largely overlooked. Herein, we explore the fundamental origins of the selectivity of the solvating extractant N,N,N′,N′-tetraoctyl diglycolamide (TODGA) for adjacent lanthanides in a liquid–liquid extraction system, which is of relevance to nuclear fuel reprocessing and rare-earth refining technologies. Complementary investigations integrating distribution studies, quantum mechanical calculations, and classical molecular dynamics simulations establish a relationship between coextracted water and lanthanide extraction by TODGA across the series, pointing to the importance of the hydrogen-bonding interactions between outer-sphere nitrate ions and water clusters in a nonpolar environment. Our findings have significant implications for the design of novel efficient separation systems and processes, emphasizing the importance of tuning both inner- and outer-sphere interactions to obtain total control over selectivity in the biphasic extraction of lanthanides.

Optimization and Single-Stage Centrifugal Contactor Experiments with the Novel Hydrophilic Complexant PyTri-Diol for the i-SANEX Process

ABSTRACTThe applicability of 2,6-bis[1-(propan-1-ol)-1,2,3-triazol-4-yl)]pyridine (PyTri-Diol) in the innovative Selective ActiNide EXtraction (i-SANEX) process as water-soluble complexing agent was studied. Preliminary batch experiments were aimed at identifying the optimal formulation of the PyTri-Diol solution and at preparing the ground for single-stage centrifugal contactor experiments. A N,N,N′,N′ tetraoctyl diglycolamide (TODGA)-based solvent loaded using a spiked synthetic Plutonium and Uranium Reduction EXtraction raffinate and the optimized PyTri-Diol aqueous phase were contacted in a single-stage annular centrifugal contactor setup with three different flow-rate conditions. No hydrodynamic problems were encountered, and promising minor actinide separation from other cations was achieved with satisfactory kinetics and stage efficiency. The flow sheet of a TODGA–PyTri-Diol-based i-SANEX process was designed exploiting batch and single-stage data, promoting the CHON compliant PyTri-Diol as excellent alternative to the formerly used SO3–Ph–BTP.

Extraction of trivalent europium and americium by the synergistic mixture of bis-1,2-dicarbollylcobaltate and N,N,N′,N′-tetraoctyl diglycolamide in highly polar 3-nitro-α,α,α-trifluorotoluene solvent

The extraction of trivalent europium and americium in the system water—HNO3—3-nitro-α,α,α-trifluorotoluene (F-3)—bis-1,2-dicarbollylcobaltate—N,N,N′,N′-tetraoctyl diglycolamide (L) has been investigated. The experimental data were treated by curve-fitting method using the LETAGROP program. It has been found that the complexes $${\text{HL}}_{{}}^{ + }$$ , $${\text{HL}}_{2}^{ + }$$ , $${\text{ML}}_{ 2}^{3 + }$$ , $${\text{ML}}_{ 3}^{3 + }$$ and $${\text{ML}}_{ 4}^{3 + }$$ (M3+ = Eu3+, Am3+) are extracted into the organic phase. The values of extraction and stability constants of the cationic complex species in F-3 saturated with water have been determined. Extraction in this system can be used for separation of lanthanides and minor actinides from PUREX process raffinate.

Applications of Diglycolamide Based Solvent Extraction Processes in Spent Nuclear Fuel Reprocessing, Part 1: TODGA

ABSTRACTOver the last decade there has been much interest in the applications of diglycolamide (DGA) ligands for the extraction of the trivalent lanthanide and actinide ions from PUREX high active raffinates or dissolved spent nuclear fuel. Of the DGAs, the N,N,N’,N’-tetraoctyldiglycolamide (TODGA) is the best known and most widely studied. A number of new actinide separation processes have been proposed based on extraction with TODGA. This review covers TODGA-based processes and extraction data, specifically focusing on how phase modifiers have been used to increase metal loading and thus enhance the operating process envelopes. Effects of third phase formation and the organic phase speciation are reviewed in this context. Relevant aspects of the extraction chemistry of important solvents (TODGA-modifier-diluent combinations) are described and their performances demonstrated by a consideration of the published flowsheet tests. It is seen that modifiers are successfully enabling the use of TODGA in actinide separation processes but to date the identification and testing of suitable modifiers has been rather empirical. There is a growing understanding of the fundamental chemistry occurring in the organic phase and how that affects extractant speciation and metal loading capacity but studies are still needed if TODGA-based flowsheets are to become an industrially deployable option for minor actinide (MA) recovery processes.

Insight into nitric acid extraction and aggregation of N, N, N’, N’-Tetraoctyl diglycolamide (TODGA) in organic solutions by molecular dynamics simulation

ABSTRACTThe molecular dynamics (MD) simulation of TODGA in n-dodecane shows formation of nanostructures of TODGA aggregates with nitric acid and water. These aggregates are dispersed in dodecane phase or form well defined reverse micelles grown sufficient in size depending on the acid concentration. With increasing nitric acid concentration, aggregation number of TODGA in reverse micelles also increases which, however, is independent of TODGA concentration. Aggregation number rises from 2 to 8 in presence of 0–3.5 M nitric acid in corresponding aqueous phase. The formation of the aggregates explains remarkable acid co-extraction from aqueous phase to organic dodecane phase by TODGA.

Adsorption behavior of thorium on N,N,N′,N′-tetraoctyldiglycolamide (TODGA) impregnated graphene aerogel

As a kind of three-dimensional graphene architecture material with superhydrophobic, low density, high specific surface area and porosity, graphene aerogel (GA) can be used to immobilize extractant to constitute the solvent impregnated adsorbent. In this paper, the N,N,N′,N′-tetraoctyldiglycolamide impregnated graphene aerogel ( GA-TODGA) was prepared to remove the thorium from aqueous solution. It is found that the adsorption of thorium on GA-TODGA is strongly dependent on the concentration of TODGA in GA and HNO3 in aqueous solution. Compared with other solvent impregnated adsorbents, the adsorption capacity of GA-TODGA is much higher due to the high immobilization capacity of GA for TODGA. Furthermore, the GA-TODGA also possesses excellent stability and reusability, ensuring the application potential of using GA-TODGA in large scale.