Tetra-n-octyldiglycolamide Research Articles

Extractive Mass Transfer of Zr(IV) into a Hydrophobic Ionic Liquid Medium Containing Diglycolamide Extractant: Solvent Extraction and Spectroscopic Analysis.

Solvent extraction of Zr(IV) in ionic liquid (IL) medium is less known and Zr(IV) - IL chemistry indeed needs exploration to realize the coordination approach of Zr(IV) in IL phase. In view of this, in the present work, a strongly hydrophobic imidazolium based IL: 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide ([C8mim][NTf2]) as the medium containing a diglycolamide (DGA) extractant: N,N,N',N'-tetra-n-octyldiglycolamide (TODGA) was opted to understand the extraction behavior of Zr(IV) from nitric acid medium. Different experimental parameters such as the concentration of initial nitric acid, initial feed metal concentration, equilibration time and ligand concentration were tuned to unravel the extraction efficiency of the proposed IL phase towards Zr(IV). The extraction scenario was completely dependent on the hydrophobicity of IL diluent and increasing extraction trend with an increase in feed acidity along with the coordination of two TODGA molecules ensured Zr(IV) - complex formation in a neutral solvation mechanistic pathway. The extraction trend of Zr(IV) was compared with molecular diluent (n-dodecane (n-DD)) containing TODGA and a phase modifier: N,N-dihexyloctanamide (DHOA). The coordination aspect of Zr(IV) with ligand in IL phase was ascertained spectroscopically to validate Zr(IV) loading in IL phase. Thermodynamics of Zr(IV) extraction revealed the nature of the extraction process and the complex formation.

Ligand structure and diluent nature in defining improved Am3+ and Cm3+ separation using diglycolamides: a combined solvent extraction and DFT study.

Separation of Am3+ and Cm3+ is one of the most challenging yet unavoidable steps in the back end of the nuclear cycle. Various ligands evaluated for Am/Cm separation have their own merits and demerits, and not a single ligand has been uniquely proposed for this purpose. In the present work, we evaluated N,N,N',N'-tetra-n-octyldiglycolamide (TODGA) vis-à-vis N,N,N',N'-tetra-2-ethylhexyldiglycolamide (T2EHDGA) in combination with a hydrophilic 2,6-bis(1,2,4-triazinyl)pyridine (SO3PhBTP) derivative in the aqueous phase for the separation of Am3+ and Cm3+ from nitric acid medium. The results showed that marginal selectivity for Am3+ over Cm3+ was observed with T2EHDGA in the presence of SO3PhBTP, which was attributed to the difference in the entropy change for their extraction from both the temperature-dependent liquid-liquid extraction and computational studies.

Selective separation of rare earth, Sr, Mo, and Zr from simulated raffinate of uranium/plutonium co-purification process

Spent fuel contains many elements including those that are radioactive. Separation and recovery of these substances have been challenging. This paper presents an efficient strategy for stepwise separation of the rare earth, strontium, molybdenum, and zirconium from the simulated raffinate of a uranium/plutonium co-purification process. This strategy employed three extractants with different metal ion selectivity, and cyclohexanediamine tetraacetic acid (CDTA) was introduced as a complexing agent to inhibit the extraction of Zr(IV) and precious metals. The recovery efficiency of all the rare earth elements was more than 97 % through the three-stage extraction, with N,N,N′,N′-tetranoctyl-diglycolamide (TODGA) as the extractant and N,N-dibutyloctanamide (DBOA) as the phase modifiers. Sr(II) was selectively recovered using N,N,N′,N′-tetracyclohexyl-diglycolamide (TCHDGA). A bisphosphonic acid extractant, N,N-hexadecylamine bis (methylene phenylphosphonic acid) (HADMPPA), was designed and synthesized for the selective separation of Zr(IV) and Mo(VI). The separation conditions of the recovered elements from other elements in each step were systematically examined. Moreover, the mechanism of the extraction reaction was investigated using FTIR spectroscopy, the slope method, and the equimolar series method. To our knowledge, this is the first time that four groups of major elements have been sequencially separated from the simulated high-level waste liquid in one process. This work could contribute to nuclear fuel reprocessing as well as the sustainable development of nuclear energy.

Triflimide Effect in Solvent Extraction of Rare-Earth Elements from Nitric Acid Solutions by TODGA

ABSTRACT Outer-sphere interactions play an important role in the liquid-liquid extraction and separation of metal ions and they could be used to tune the efficiency and selectivity of recovery. Here, we report the extraction behaviour and separation of trivalent rare-earth elements from aqueous nitric acid solutions with N,N,N’,N’-tetra-n-octyl diglycolamide (TODGA), which was preliminarily contacted with an aqueous solution of N-H acid bis[(trifluoromethyl)sulfonyl]imide (triflimide, HTf2N; Tf = CF3SO2) resulting in an adduct TODGA⋅HTf2N. We examined in detail the extraction system composed of TODGA acidified with HTf2N and 1,2-dichloroethane as diluent. The effect of various experimental conditions such as the nature of diluent, aqueous nitric acid concentration, and TODGA⋅HTf2N concentration in the organic phase was studied. It has been found that the distribution coefficient values for metal ions are much greater, especially at low aqueous acidity in the extraction systems with the acidified organic solvent phase. Furthermore, the heavier lanthanides were effectively extracted and the intergroup lanthanide selectivity was greatly improved (separation factors for the Lu/La pair increased by 40 and 2 times for the two systems under study, respectively).

Selective actinide(III) separation using 2,6-bis[1-(propan-1-ol)-1,2,3-triazol-4-yl]pyridine (PyTri-Diol) in the innovative-SANEX process: laboratory scale counter current centrifugal contactor demonstration

Abstract An innovative-SANEX process for the selective separation of the trivalent actinides americium and curium from a simulated PUREX raffinate solution was successfully demonstrated on the laboratory scale using a 16-stage 1 cm annular centrifugal contactor setup. The solvent was composed of 0.2 mol L−1 N,N,N′,N′-tetra-n-octyl-diglycolamide (TODGA) and 5% v/v 1-octanol in a kerosene diluent. Zr(IV) and Pd(II) co-extraction was prevented using trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (CDTA) as a masking agent in the feed. The actinide(III) selective back-extraction was achieved using 2,6-bis[1-(propan-1-ol)-1,2,3-triazol-4-yl]pyridine (PyTri-Diol) in 0.45 mol L−1 HNO3 as a CHON alternative to the sulfur-containing stripping agent used in a previous version of the innovative-SANEX process. The new process described in this paper showed excellent performance for the recovery of An(III). An An(III) product with a quasi-quantitative recovery of americium and curium (≥99.9%) and very good separation from fission and activation products was obtained (decontamination factors ≥4000). Only a slight contamination with Zr and Ru was observed. This test demonstrates the successful use of molecules containing only carbon, hydrogen, oxygen, and nitrogen atoms (so-called CHON molecules) for the selective separation of An(III) from a simulated PUREX raffinate solution. By avoiding sulfur- or phosphorous-containing molecules, the generation of secondary radioactive waste during process operation can be reduced drastically.

Highly efficient uptake of Europium (III) and Americium (III) from acidic feeds using extraction chromatography resins containing N,N,N’,N’-tetra alkyl diglycolamides with varying alkyl chain length in an ionic liquid

A comparative study on the uptake of Eu(III) and Am(III) was carried out using four extraction chromatography (XC) resins impregnated with constant weight of the tetra-n-pentyl diglycolamide (TPDGA) ligands, viz. tetra-n-hexyl diglycolamide (THDGA), tetra-n-octyl diglycolamide (TODGA) and tetra-n-decyl diglycolamide (TDDGA) along with C4mim·NTf2, a room temperature ionic liquid (RTIL), from nitric acid feed solutions. The uptake of Eu(III) was higher than that of Am(III) while the uptake trend with the four XC resins followed the order: TPDGA > THDGA > TODGA > TDDGA, which was opposite to the alkyl chain length attached to the DGA extractant. When constant moles of the extractants were used, the observed trend was TODGA > THDGA > TDDGA > TPDGA. Also, for all the four XC resins, the uptake of both Eu(III) and Am(III) ions increased with increasing nitric acid concentration. The uptake data with all the four resins were fitted into different kinetic and isotherm models which conformed to a pseudo-second order kinetics and Langmuir monolayer sorption isotherm. Furthermore, columns were prepared with these XC resins and were used to obtain breakthrough profiles using a feed solution containing 0.55g/L Eu(III) in 3M HNO3. Subsequently, the elution of the loaded metal ion from the column was accomplished with a strippant solution containing 1M guanidine carbonate+0.05M EDTA in distilled water. Elution profiles for all the four resins showed sharp peaks with almost no tailing.

Highly efficient Plutonium(IV) uptake from acidic feeds using four extraction chromatography resins containing diglycolamides and ionic liquid

Quantitative recovery of plutonium from lean effluents is one of the most challenging tasks for separation scientists. Four extraction chromatography (XC) resins containing substituted diglycolamide ligands viz. N,N,N',N'-tetra-n-pentyl diglycolamide (TPDGA), N,N,N',N'-tetra-n-hexyl diglycolamide (THDGA), N,N,N',N'-tetra-n-octyl diglycolamide (TODGA) and N,N,N',N'-tetra-n-decyl diglycolamide (TDDGA) and a room temperature ionic liquid (RTIL) were tested for the extraction of plutonium (IV) from nitric acid feed solutions. The relative efficiency of uptake of the metal ion in the entire range of HNO3 studied was: TPDGA > THDGA > TODGA > TDDGA, which was opposite to the chain length of the attached alkyl groups. Also, for all the four XC resins the uptake of Pu(IV) was found to decrease with increasing nitric acid concentration in the lower acidity range followed by an increase thereafter. The uptake of Pu(IV) with all the four XC resins was fitted into different kinetic and isotherm models. It was found that all the four resins followed the pseudo-second order kinetic model and Langmuir monolayer adsorption model. Column studies with these XC resins using a loading solution containing 1.2g/L Pu(IV) in 3M HNO3 showed early breakthrough for the higher homolog DGA ligands as compared to the lower homologs. Effective elution of the loaded Pu(IV) from the column was done in about 5.5 column volumes using a solution containing 0.5M oxalic acid in 0.5M HNO3.

Gamma radiolytic stability of the novel modified diglycolamide 2,2'-oxybis(N,N-didecylpropanamide) (mTDDGA) for grouped actinide extraction.

Reprocessing of spent nuclear fuel aims at improving resource efficiency and reducing its radiotoxicity and heat production in the long term. The necessary separation of certain metal ions from the spent fuel solutions can be achieved using different solvent extraction processes. For the scenario of the EURO-GANEX process, the use of the new, modified diglycolamide 2,2′-oxybis(N,N-didecylpropanamide) (mTDDGA) was recently proposed to simplify the current solvent composition and reduce extraction of fission products. Before further developing the process based on this new ligand, its stability under ionizing radiation conditions needs to be studied. For this reason, gamma irradiation experiments were conducted followed by analyses with high performance liquid chromatography coupled to a mass spectrometer (HPLC-MS). The determined degradation rate of mTDDGA was found to be lower than that of the reference molecule N,N,N′,N′-tetra-n-octyl-diglycolamide (TODGA). Many identified degradation compounds of both molecules are analogues showing the same bond breaking, although also unreported de-methylation, double/triple de-alkylation and n-dodecane addition products were observed.

Aqueous soluble ‘N′ donor heterocyclic ligands for the mutual separation of Am3+ and Eu3+: Solvent extraction, flat sheet supported liquid membrane and hollow fiber microextraction studies

Preferential stripping of the trivalent actinide ions such as Am(III) from the organic extract containing a mixture of Am(III) and Eu(III) by a suitable separation method is one of the most challenging areas of research which can find application in the radioactive waste management scheme. In the present study, a comparative evaluation of aqueous soluble tetrasulphonated derivatives of bis-triazinyl pyridine (BTP, LI), bis-triazinyl bipyridine (BTBP, LII) and bis-triazinyl phenanthroline (BTPhen, LIII) was done for the preferential stripping of Am(III) from a mixture of Am(III)/Eu(III) in the N,N,N′,N′-tetra-n-octyl diglycolamide (TODGA) extract. The results obtained in the solvent extraction studies were used for setting up of flat sheet supported liquid membrane based separation systems where the feed phase contained 1 M HNO3 spiked with the 241Am and 152,154Eu radiotracers while the receiver phase contained 0.01 M solutions of the aqueous soluble complexing agents in the presence of 1 M HNO3. Analogous studies were carried out using polypropylene hollow fibers leading to micro extraction of both Am(III) and Eu(III) and preferential stripping of Am(III) where promising separation behavior was observed, especially in the cases of LI and LIII with the DF values of 66 and 72, respectively for Am3+ over Eu3+ along with >80% recovery of Am.

Extraction of Selected Metal Ions with Mixtures of N,N,N’,N’-tetra-n-octyldiglycolamide and 4,4′(5′)-di-t-butylcyclohexano 18-crown-6

ABSTRACT Previous work has shown that solvent extraction (SX) and extraction chromatography (EXC) systems containing mixtures of extractants can be utilized to impart selectivity and improved physical characteristics that were not achievable with a single extractant. In an effort to discover EXC materials with unique selectivity and improved physical properties, we studied the extraction of selected metal ions from nitric acid and hydrochloric acid by EXC resins prepared from mixtures of N,N,N’,N’-tetra-n-octyldiglycolamide (TODGA) and 4,4′(5′)-di-t-butylcyclohexano 18-crown-6 (dtBCH18C6). Except for enhanced extraction of Ra and Ba from dilute HNO3, the EXC resins essentially exhibited the metal ion extraction properties expected from materials prepared with the individual extractants. The origin of the Ra/Ba enhancement was studied by solvent extraction variation studies in 1-octanol and n-dodecane and on extraction chromatography resins, indicating that the enhancement may not be a true synergistic interaction between the extractants, but a phase modification by the TODGA related to the co-extraction of HNO3 and water. Additionally, the influence of alkyl substituents on the DGA extractant and potential applications of the mixed extractant system in analytical chemistry and nuclear medicine were explored with extraction chromatography resins prepared from the extractant mixtures.

Selective permeation of 90Y from a mixture of 90Y/90Sr through diglycolamide impregnated supported liquid membranes

An attempt was made in this work to evaluate a simple flat sheet supported liquid membrane technique for the separation of carrier free 90Y from 90Sr using two diglycolamide carrier ligands, (i) N,N,N′,N′-tetra-n-octyl-diglycolamide (TODGA), and (ii) N,N,N′,N′-tetra-(2-ethylhexyl)-diglycolamide (TEHDGA). Various experimental parameters were optimized to get selective transport of 90Y over 90Sr. At 6 M HNO3 feed acidity, >95% 90Y could be recovered selectively in just 4 h with both the ligands. Under identical experimental conditions, about 0.1% transport of Sr was also recorded which could be completely removed by passing through a Sr selective column to get medical grade 90Y pure product. A mathematical model equation was also derived and experimentally validated for predicting the transport of 90Y through membrane.

Selective extraction of trivalent actinides using CyMe4BTPhen in the ionic liquid Aliquat-336 nitrate.

The extraction of Am(iii), Cm(iii) and Eu(iii) by 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline (CyMe4BTPhen) from nitric acid solution was studied using the ionic liquid Aliquat-336 nitrate ([A336][NO3]) as diluent. Results show a high selectivity of the solvent for Am(iii) and Cm(iii) over Eu(iii), but rather slow extraction kinetics. The kinetics of CyMe4BTPhen were largely improved by the addition of 0.005 mol L−1N,N,N′,N′-tetra-n-octyl-diglycolamide (TODGA) as a phase transfer reagent and by the use of 1-octanol as co-diluent. The addition of the phase transfer catalyst and co-diluent did not compromise the selectivity towards the actinide/lanthanide separation and thus this four-component system can be successfully applied to separate Am(iii) and Cm(iii) from the lanthanides.

Separation of Pt(IV), Pd(II), and Rh(III) from Chloride Solutions by Multistage Extraction Using Nitrogen-Containing Extractants

This article demonstrates possible separation of Pd(II), Pt(IV), and Rh(III) ions from chloride solutions by solvent extraction in rotating coiled columns (RCC). The most common reagents used for extraction of platinum metals were selected as extractants: trioctylamine (TOA), methyltrialkylammonium chloride (MTAA), tributyl phosphate (TBP), and relatively new reagent—N,N,N',N'-tetra-n-octyldiglycolamide (TODGA). The completeness of extraction of platinum metals from individual and mixed hydrochloric acid and chloride solutions has been analyzed as a function of the essence and concentration of extractant, acidity of the analyzed solutions, and other factors. Optimum conditions of quantitative extraction of the metals from model hydrochloric acid and chloride solutions into the extractant phase have been determined, including subsequent selective separation at the re-extraction stage. A flowchart has been proposed for multistage extraction of Pd(II), Pt(IV), and Rh(III) using 0.05 M MTAA solution in toluene as a stationary phase in RCC. The flowchart includes extraction of Pd(II) and Pt(IV) ions from the solution (0.1 M HCl + 30 g/L Cl–) into the organic phase upon simultaneous separation of Rh(III) remaining in the aqueous phase and consecutive re-extraction of Pd(II) and Pt(IV) from the organic phase using 0.01 M solution of thiourea in 0.1 M HCl and 1 M solution of thiourea in 0.5 M HCl, respectively. The flowchart has been verified for separation of platinum metals in the production process of preset composition. The degree of metal extraction after processing by 0.05 M solution of MTAA in in toluene and consecutive re-extraction by solutions of thiourea is 99.5% for rhodium(III), 99.9% for palladium(II), and 97.4% for platinum(IV). The extracted aqueous phases of rhodium and platinum after output from the column did not contain impurities of other platinum metals. In the aqueous fraction of palladium, the platinum content was 0.5%.

Thermal stability of the extraction system “TODGA in Isopar M with n-decanol” at above atmospheric pressure

The gas evolution dynamics has been studied during thermal oxidation of 0.15 and 0.2 mol L−1 solutions of N,N,N′,N’-tetra-n-octyldiglycolamide (TODGA) in Isopar M diluent with n-decanol depending on the concentration of nitric acid. The effect of irradiation of the system “TODGA in Isopar M with n-decanol” on the possibility of a thermal explosion has been determined. Weak exothermic effects were observed for non-irradiated and irradiated mixtures in the presence of 4 mol L−1 HNO3 at 170 °C. At a concentration of nitric acid in the aqueous phase of 8 mol L−1 or more, for non-irradiated and irradiated two-phase systems, the process passes into a thermal explosion mode.

Oxidative digestion of spent sulfocationites containing radioactive rare earth and transplutonium elements

In this work, the chemical digestion conditions for spent KU-2 × 8 sulfocationites manufactured in Russia were investigated. It was shown that the complete oxidative digestion of the ionites could be performed in solutions of H2O2 and HNO3 in the presence of Fe3+ ions adsorbed on the resin as an oxidation catalyst. The total digestion time of the resin was studied as a function of the presence of the digestion catalysts, solid-to-liquid phase ratio, process temperature, Fe3+ ion content in the solid sulfocationite phase, and the divinylbenzene (DVB) cross-linking agent content of the ionite. A possibility for the removal of rare earth element (REE) and transplutonium element (TPE) radionuclides from the solution of the digested sulfocationite was shown by the sorption technique using the tetra-n-octyldiglycolamide (TODGA)-based sorbent.

Solvent extraction fractionation of manganese, cobalt, nickel and lithium using ionic liquids and deep eutectic solvents

The recycling of spent lithium-ion batteries remains a challenging task due to the complexity of the leach liquors, which contains several metals in acidic solution. The recovery of valuable metals, viz. Co, Li, Mn, Ni, is also difficult due to the similar chemical behavior of the divalent metal ions. Solvent extraction is mainly used for the separation of these metals, but the conventional extractants used in combination with molecular diluents usually lack of selectivity. We report a new solvent extraction system based on N,N,N',N'-Tetra-n-octyldiglycolamide (TODGA) diluted in the room temperature hydrophobic ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Up to 99% of manganese can be extracted in one step with separation factors in the range 40–60 for Mn/Co separation and higher than 200 for the other metals. The mechanism of extraction was detailed. Cobalt separation was done using the ionic liquid tri-hexyltetradecylphosphonium chloride. More than 90% of cobalt can be extracted with very high separation factors. Nickel and lithium separation was carried out by deep eutectic solvents (DESs) based on lidocaine and carboxylic acids. The use of a DES made of decanoic acid and lidocaine shows a high extraction efficiency for nickel while lithium is left in solution.

Thermochemical Stability of Extraction Systems for SNF Processing

Thermal stability of extraction systems containing N,N,N′,N ′-tetra-n-octyldiglycolamide (TODGA), di(N-ethyl-4-hexylanilide) 2,2′-bipyridine-6,6′-dicarboxylic acid (DYP-7), di(N-ethyl-4-fluoroanilide) of 2,6-pyridinecarboxylic acid Et(pFPh)DPA, di(N -ethyl-4-ethylanilide) of 2,2′-bipyridine-6,6′-dicarboxylic acid (DYP-9) under the conditions capable of causing emergencies, i.e., those unfavorable as regards the fire and explosion safety. It was found that irradiation with accelerated electrons of a TODGA–Isopar-М mixture in an n-alcohol affects the possibility of a thermal explosion and shown that the irradiation is accompanied by an intense evolution of gases. The possibility of passing from the oxidation of organic components of the system by nitric acid to the burning and explosion mode was evaluated. It was found that, with diamides used, the pressures of gaseous products of exothermic reactions are substantially lower than those with TODGA and TBP, which makes them promising extracting mixtures as regards the safety of the technological process.

Solvent extraction of intra-lanthanides using a mixture of TBP and TODGA in ionic liquid

The recovery and separation of trivalent lanthanides into individual elements is difficult owing to their similar chemical behaviours. In this study, the solvent extraction of trivalent lanthanide ions from nitric acid solutions in an organic phase comprising a mixture of two electrically neutral extractants, viz. tri(n-butyl)phosphate (TBP) and N,N,N′,N′-tetra(n-octyl)diglycolamide (TODGA), is investigated. The hydrophobic room-temperature ionic liquid (IL), 1-methyl-3-butyl-imidazolium bis(trifluoromethanesulfonyl)imide, is employed as a more environmentally benign diluent compared to the conventional molecular solvents. The results reveal that the addition of TBP as a co-extractant with TODGA not only significantly enhances the metal ion extraction but also affords high intra-lanthanide ion selectivity. This is attributed to the formation of complex lanthanide species with both TBP and TODGA. In addition, when IL is used as a diluent, the cationic exchange between metal–organic ligand species and IL cations, as well as neutral complex extraction result in a more efficient extraction. Moreover, the hydrophobic anionic IL entities can also be involved in the extraction mechanism, affording lipophilic metal–organic ligand complexes. The synergistic solvent combination of TODGA, TBP, and IL can afford an excellent separation of the lanthanide(III) ions.

Effect of irradiation on the oxidation kinetics of TODGA-based extraction mixtures at atmospheric pressure

The gas evolution from mixtures consisting of 0.2 M solution of N,N,N′,N′-tetra-n-octyldiglycolamide (TODGA) in n-alcohol (n-decanol or n-nonanol) with Isopar-M diluent was investigated during thermal oxidation. The effect of ionizing radiation on their thermal stability has been studied. It has been determined that the volume of gaseous thermolysis products increases by 260% in the case of n-nonanol and 80% in the case of n-decanol compared to non-irradiated solutions. It has been shown that the gas evolution rate and gas volume increase when the irradiated mixture saturated with nitric acid is heated. However, there are no prerequisites for the development of autocatalytic oxidation.

Multiscale investigations of europium(iii) complexation with tetra-n-octyl diglycolamide confined in porous solid supports

Functionalized ordered mesoporous carbons facilitate the templateing of microcrystalline-like domains and multinuclear speciation under high Eu3+ loading conditions.