Tetradecyl Malonamide Research Articles

Understanding the complexation of the Eu3+ ion with TODGA, CMPO, TOPO and DMDBTDMA: Extraction, luminescence and theoretical investigation

A comparative study was carried out to understand the complexation behavior of the Eu3+ ion with important reagents, namely TODGA (N,N,N′,N′ tetraoctyl diglycolamide), CMPO (octyl (phenyl)-N, N-diisobutyl carbamoyl methyl phosphine oxide), DMDBTDMA (dimethyl dibutyl tetradecyl malonamide) and TOPO (tri-n-octyl phosphine oxide) in dodecane, used for the separation of actinides and lanthanides from lab and nuclear high-level wastes, by experimental (extraction and luminescent) and theoretical means. A solvent extraction study revealed the metal–ligand stoichiometry as 1:3 for all the systems with the extraction efficiency TOPO>CMPO>TODGA>DMDBTDMA at 1M HNO3, while TODGA>CMPO>DMDBTDMA>TOPO at 3M HNO3. A luminescence investigation revealed the presence of single species in the extracted complex for all the systems, with no inner sphere water molecules for all the systems except for DMDBTDMA which had one inner sphere water molecule. The high intensity of the 5D0–7F2 transition revealed the presence of Eu3+ ions in an asymmetric environment with the local point group symmetry C3v for the TODGA and DMDBTDMA complexes, compared to C3h symmetry for the CMPO and TOPO complexes. Judd–Offelt parameters, radiative, non-radiative lifetimes, branching ratio, transition probabilities and quantum efficiencies for all the complexes were estimated and compared. Three O-donor atoms from each TODGA molecule coordinated to the Eu3+ ion in the first coordination sphere, while three CMPO units were found to be coordinated in a monodentate fashion. For the Eu-TOPO complex, three O donor atoms from each of the three TOPO molecules and six O donor atoms from three nitrate ions were coordinated. Out of three DMDBTDMA ligands, one was found to be coordinated in a bidentate mode, whereas two were in a monodentate mode, along with three nitrate ligands bonding in a monodentate fashion.

Aqueous Partitioning of Minor Actinides by Different Processes

Actinide partitioning is a proposed strategy for effective mitigation of the long-term hazards associated with high-level waste (HLW). Octyl-(phenyl)–N,N-diisobutyl carbamoyl methyl phosphine oxide (CMPO) and diphenyl–N,N-diisobutyl carbamoyl methyl phosphine oxide (DφCMPO) are amongst the promising extractants extensively studied since the 1980s for actinide partitioning from wastes of different origin. During the last two decades, substituted malonamide extractants such as N,N'-dimethyl-N,N'-dibutyl tetradecyl malonamide (DMDBTDMA) and N,N'-dimethyl-N,N'-dioctyl hexylethoxy malonamide (DMDOHEMA) have emerged as viable green alternatives to phosphine oxides. During the last decade, diglycolamide-based extractants such as N,N,N′,N′-tetraoctyl diglycolamide (TODGA) and N,N,N′,N′-tetra-2-ethylhexyl diglycolamide (TEHDGA) have received considerable attention due to overwhelmingly favourable extraction and stripping efficiencies of minor actinides from different types of transuranium (TRU) wastes. The focus of the present review is to carry out comparative evaluation of the key physical and chemical properties of these extractants for hydrometallurgical applications. Merits of flow sheets proposed for the separation and recovery of minor actinides from high-level wastes have also been discussed.

Separation and determination of components of high level waste using IC and dynamically modified reversed-phase HPLC in ‘actinide partitioning’ studies using synthetic waste solution

Ion-chromatography (IC) as well as high performance liquid chromatography (HPLC) techniques have been used as analytical tools for the separation and estimation of some of the relevant metal ions present in the high level liquid waste (HLLW). IC was applied for the estimation of alkali and alkali earth metal ions, viz. Na, Cs, Ba and Sr using methane sulphonic acid as the eluent on a cation exchange column. On the other hand, dynamically modified (with sodium salt of n-octane sulphonic acid) reverse phase HPLC was followed for the estimation of lanthanides viz. La, Pr, Nd and Sm using α-hydroxy isobutyric acid as the eluent on a C-18 column. Sample acidity of 0.01 M HNO3 was optimized for best analytical results. The interferences of one group of metal ions on the quantification of the other group of metal ions were studied. The solvent extraction data (distribution coefficient data) of Na, Cs, Sr, Ba, La, Pr, Nd and Sm from their mixture was obtained by analyses of the aqueous samples before and after extraction with extractants used for actinide partitioning, viz., octyl(phenyl)N,N-diisobutyl carbamoyl methylene phosphine oxide (CMPO), N,N′-dimethyl-N,N′-dibutyl tetradecyl malonamide (DMDBTDMA) and N,N,N′,N′-tetraoctyl diglycolamide (TODGA). The solvent extraction data obtained by IC/HPLC techniques was compared with those obtained by ICP-AES technique. A good agreement between the results of the two techniques validated the present analytical method.

Application of N,N′‐Dimethyl‐N,N′‐Di(4‐Chlorophenyl)Tetradecyl Malonamide for the Selective Recovery of Iron(III) from Concentrated Chloride Solutions

The feasibility of using two new diamides namely; N,N′‐dimethyl‐N,N′‐di(4‐chlorophenyl)malonamide (DMDPhClMA) and N,N′‐dimethyl‐N,N′‐di(4‐chlorophenyl)tetradecylmalonamide (DMDPhClTDMA), as agents for the selective extraction of iron(III) from chloride solution was investigated. A systematic investigation has been carried out on the detailed extraction properties of iron(III) with these extractants from chloride media. The extraction of iron(III) from an aqueous chloride solution in the presence of metal ions, such as Zn(II), Co(II), Mn(II) Cu(II), Pb(II), Ni(II) and Ag(I) was carried out using DMDPhClMA or DMDPhClTDMA in binary and multicomponent mixtures. The quantitative extraction of iron(III) with DMDPhClMA and DMDPhClTDMA in toluene is observed at 4 and 7 M HCl, respectively. The quantitative stripping of Fe(III), from the loaded organic phase was successfully achieved by simple contact with water.

N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide impregnated magnetic particles for the uptake of lanthanides and actinides from nuclear waste streams

A novel, simple technique based on magnetically assisted chemical separation (MACS) has been developed for the uptake of lanthanides and actinides from pure nitric acid solutions as well as from Simulated Pressurized Heavy Water Reactor-High Level Waste (PHWR-SHLW). Uptake profiles of various metal ions, such as Pu(IV), U(VI), Th(IV), Am(III), Eu(III), Sr(II), Cs(I) and Fe(III) were investigated as a function of time and nitric acid concentrations usingN,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) impregnated magnetic particles and compared withN,N′-dimethyl-N,N′-dibutyl tetradecyl malonamide (DMDBTDMA) and trialkyl phosphine oxide coated magnetic particles and also with TODGA coated extraction chromatographic resins. The uptake of various metal ions follows the order Eu(III) > Am(III) > Th(IV) > Pu(IV) > U(VI) > Sr(II) > Fe(III) > Cs(I) in pure nitric acid solutions. On the other hand, distinctly high distribution coefficient (Kd) value has been observed for Pu(IV) as compared to Eu(III) and Am(III) in SHLW. Further, no significant extraction of Cs(I) or Sr(II) was observed in SHLW. Also, at any acidity theKdvalue of a given metal ion is less in the SHLW as compared to that in pure HNO3, apparently due to the co-extraction of the other metal ions present in SHLW. The loading capacity of the TODGA impregnated magnetic particles with respect to Th(IV), U(VI) and Eu(III) was determined, along with the distribution isotherms to simulate multiple contacts. The adsorption models of Langmuir and Freundlich were fitted to the experimental data and best correlations was obtained for Langmuir model suggesting monolayer adsorption is the prevalent mechanism. The stability and reusability of the TODGA coated magnetic particles was also assessed.

Relation between the hydrophile/hydrophobe ratio of malonamide extractants and the stability of the organic phase: investigation at high extractant concentrations

In the present paper, it is shown that in malonamide extractant/dodecane mixtures, change in the shape of the extractant aggregate may promote phase demixion. This phenomenon is known as the 3rd phase formation in extractant systems. The shape of the aggregates is dictated by the length of the alkyl chains stabilizing the reverse microemulsion by steric repulsion. Small angle scattering experiments are used to investigate the aggregation states of diamide extractant molecules, namely N,N'dimethyl-N,N'dibutyl-tetradecyl malonamide (DMDBTDMA) and N,N'dimethyl-N,N'dibutyl-pentyl malonamide (DMDBPMA), in dodecane. The results are described in a consistent way by the packing parameter concept and by expressing steric repulsion versus Van der Waals inter-aggregate interactions, both curvature dependants. Non-monotonous change in the extractant Critical Micellar Concentration (CMC) as a function of the extractant alkyl chain length is rationalized by comparing Van der Waals attraction between the alkyl chains of both the extractant and the solvent.

Extraction of actinides using N, N, N′, N′-tetraoctyl diglycolamide (TODGA): a thermodynamic study

Summary The effect of temperature on the extraction behaviour of Am(III), Pu(IV) and U(VI) from nitric acid medium was studied employing N,N,N′,N′-tetraoctyl diglycolamide (TODGA) in n-dodecane. The two-phase equilibrium constants (log K′ex) were calculated and compared with those of other extractants proposed for actinide partitioning, viz. octyl-(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) and N,N,N′,N′-dimethyl dibutyl tetradecyl malonamide (DMDBTDMA). Thermodynamic parameters, viz. ΔG, ΔH and ΔS for the extraction of actinides by TODGA were also compared with those of CMPO and DMDBTDMA. These studies indicate that the extraction processes of Am(III) and U(VI) are enthalpy driven whereas entropy factor counteracts the extraction. However, in the case of Pu(IV), the extraction process is enthalpy as well as entropy favoured. Role of diluent on the loading of Nd(III) in 0.1 M TODGA has also been investigated.

N, N′-dimethyl-N, N′-dibutyl tetradecyl malonamide impregnated magnetic particles for the extraction and separation of radionuclides from nuclear waste streams

Summary N, N′-dimethyl-N, N′-dibutyl tetradecyl malonamide (DMDBTDMA) coated magnetic particles are being evaluated for the possible application in the partitioning of actinides, lanthanides and fission products from pure nitric acid solutions as well as from Simulated Pressurized Heavy Water Reactor-High Level Waste (PHWR-SHLW). Uptake profiles of various metal ions, such as Pu(IV), U(VI), Am(III), Eu(III), Sr(II) and Cs(I) were obtained as a function of time and nitric acid concentration by batch studies using DMDBTDMA coated magnetic particles. The order of uptake follows the order Pu(IV)>U(VI)>Am(III)>Eu(III)>Sr(II)∼Cs(I) in both nitric acid and SHLW. The uptake of various trivalent lanthanides was also investigated as a function of nitric acid concentration and found the uptake order as Pr(III)>La(III)>Eu(III)>Tb(III)>Ho(III)>Er(III)>Yb(III)>Lu(III). The sorption capacity of the DMDBTDMA coated magnetic particles with respect to U(VI) and Eu(III) was determined, along with the sorption isotherms to simulate multiple contacts. The maximum sorption capacity of DMDBTDMA coated magnetic particles was found to be 1.58 mmol/g and 0.36 mmol/g for U(VI) and Eu(III), respectively. The adsorption models of Langmuir and Freundlich were fitted to the experimental data and best correlations were obtained for both the models. The Langmuir model predicts a loading capacity of 1.61 mmol/g and 0.37 mmol/g for U(VI) and Eu(III), respectively, which is close to the experimental values. The stability and recycling capacity of the DMDBTDMA coated magnetic particles was also assessed.

Factorial designs as tools to study the influence of thermal oxidation factors on substituted malonamide destruction

The thermal oxidation of two potential extractants for minor actinides in nuclear fuel reprocessing was investigated. These extractants were N, N′-dimethyl, N, N′-dibutyl, tetradecyl malonamide (DMDBTDMA), used as a model, and N, N′-dimethyl, N, N′-dibutyl, dodecylethoxy malonamide (DMDBDDEMA), used as a modified structure. An experimental methodology with two factorial designs was used to quantify the influence of different factors. In the first design, the factors were reaction time, temperature and oxidant type for experiments carried out on a pure solution of DMDBTDMA. The influence of temperature was clearly shown in the range of 200–250 °C. In the second design, the temperature was fixed at 250 °C, the humidity factor was introduced and experiments were carried out on a 0.5 mol l −1 solution of DMDBTDMA in n-dodecane, which represents the extractant concentration in nuclear fuel waste processing. This second series confirmed the efficiency of oxygen for destroying diamides. The results of thermal destruction were also compared with data photo-oxidation. Coupled experiments were also performed combining first photo-oxidation and secondly thermal oxidation with oxygen. This combination destroyed more than 99% of initial diamides.

Amides and diamides as promising extractants in the back end of the nuclear fuel cycle: an overview

Abstract An overview of the work carried out on the development of amides/diamides as alternate extractants in the back end of fuel cycle has been given. Whereas a straight chain amide, viz. N,N-dihexyl octanamide (DHOA) is a promising alternate to tri-n-butyl phosphate (TBP) in the reprocessing of irradiated uranium-based fuels, a branched chain amide, viz. N,N-di(2-ethylhexyl) isobutyramide (D2EHIBA) has been found suitable for the selective recovery of 233 U from irradiated Th. DHOA has been found to extract Pu more efficiently than TBP under uranium loading conditions. On the other hand, significant improvement in the separation of 233 U from Th and fission products has been achieved by employing 0.5 M D2EHIBA in n-dodecane as compared to that of 5% TBP (the THOREX solvent). Stripping behaviour of U for DHOA and D2EHIBA is better than that of TBP. N,N′,N,N′-dimethyl dibutyl tetradecyl malonamide (DMDBTDMA) has been evaluated for the partitioning of minor actinides (MA) from high-level nuclear waste with large uranium content (∼20 g/l). Designed amide ligands, viz. D2EHIBA showed improved separation of the desired actinide constituents like Pu (mainly 239 Pu ) and 233 U over the fission products and the major matrix elements like U and Th.

Photo-oxidation of tertiary amides, main degradation products of large malonamides

Photo-oxidation of large malonamides N, N′-dimethyl, N, N′-dibutyl, tetradecyl malonamide (DMDBTDMA) and N, N′-dimethyl, N, N′-dibutyl, dodecylethoxy malonamide (DMDBDDEMA)—potential extractants for minor actinides in nuclear fuel reprocessing—leads mainly to the corresponding monoamides: N-butyl N-methyl hexadecanamide (BMHDA) and N-butyl N-methyl dodecyl oxy butanamide (BMDDOBA), respectively. The evolution of these main photoproducts was monitored during the degradation of malonamide solutions, and also pure monoamide solutions. Irradiation, for 1 h, with a low mercury pressure lamp can destroy BMHDA when diluted to 0.075 mol l −1 in n-dodecane. The two monoamides only differ by an ether bond and the weakness introduced by such a function in an alkyl chain is shown by slightly faster degradation. The relative weakness of BMDDOBA is independent of oxidant addition. Global degradation can be monitored by GC/FID or UV detection at 200 nm.

Photo-oxidation of two malonamides, extractant models for minor actinides in nuclear fuel reprocessing

The photo-oxidation of two potential extractants, the N, N′-dimethyl, N, N′-dibutyl, tetradecyl malonamide (DMDBTDMA) and the N, N′-dimethyl, N, N′-dibutyl, dodecylethoxy malonamide (DMDBDDEMA) for minor actinides in nuclear fuel reprocessing was followed. The main photoproducts, identified by coupled techniques (GC/FTIR and GC/MS) are malonamides, monoamides and carbonylate derivatives. An irradiation, for 1 h, with a low mercury pressure lamp can destroy initial diamides diluted at 0.075 mol l −1 in n-dodecane. With pure solutions of diamides (2.05 mol l −1), destruction needs several hours to be complete. Both diamides only differ by an ether bond, their reactivity under different conditions of photo-oxidation is discussed.

Development of the Diamex Process for Treating PHWR High-Level Liquid Waste

The extraction behavior of actinides like U(VI), Pu(IV), and Am(III) as well as of fission products like Tc(VII), Zr(IV), Eu(III), and structural material Fe(III) using nitric acid/simulated pressurized heavy water reactor-high-level waste solution as aqueous phase and N,N’-dimethyl-N,N’ dibutyl tetra decyl malonamide (DMDBTDMA) in n-dodecane as solvent was investigated. The present work contributes significantly toward the development of nonphosphorous (environmentally friendly) extractant capable of partitioning long-lived actinides and fission products like 99Tc from relatively short lived fission products like 90Sr and 137Cs as well as inactive components present in high-level waste. The DAm values determined in the temperature range between 15 and 45°C showed a gradual decrease with increase in temperature throughout the acidity range. The effect of N,N di-2-ethylhexyl acetamide (D2EHAA) as phase modifier on the physicochemical properties of DMDBTDMA/n-dodecane solvent was investigated and could be correlated with parameters like the limiting organic concentration value of HNO3, DAm, or phase disengagement time. Overall comparison of diamide extraction (Diamex) and transuranium extraction (Truex) solvents has been made.

Thermal oxidation of two malonamides, extractants for minor actinides in nuclear fuel reprocessing

In this study, the thermal destruction of two potential extractants — the N, N′-dimethyl, N, N′-dibutyl, tetradecyl malonamide (DMDBTDMA) and the N, N′-dimethyl, N, N′-dibutyl, dodecylethoxy malonamide (DMDBDDEMA) — for minor actinides in nuclear fuel reprocessing was compared. The thermal destruction of a main by-product, the larger monoamide formed, was also studied for each extractant. Experiments were carried out in small reactors (closed or open) with different oxidising atmospheres. The recuperation of the syrupy degradation mixture, with ethyl acetate, was the first step of analysis before separation by Gas Chromatography (GC). The quantitation of separated by-products was performed with a Flame Ionisation Detector (FID) and the identification was realized by both Fourier Transform Infrared Spectroscopy (FTIR) and Mass Spectrometry (MS). Several by-products are identified and are obtained by cleavages of covalent bond and/or oxidation. After 1 h at 250°C, under oxygen flow in an open reactor, residual levels of DMDBTDMA and DMDBDDEMA pure solutions are 10 and 12% respectively, showing that the behaviour of both diamides seems similar. However, the destruction level of initial molecule do not inform on the global degradation of such complex structures. Initial diamides can lose their methyl and/or butyl groups and then give another malonamides. Its can also lead to monoamide by cleavage of CCO malonamide bond. One of these monoamide, the major by-product, can represent 13% of conversion from initial diamide with conditions described previously. An index of degradation based on the molecular weight of residual products, was calculated so as to compare the efficiency of thermal oxidation. Behaviour of diamides was also followed by thermal differential analysis (TDA) and thermal gravimetric analysis (TGA) coupled with FTIR. These techniques has shown that carbon dioxide can be produced at temperature around 250°C.

Substituted malonamides as extractants for partitioning of actinides from nuclear waste solutions

Pentaalkyl malonamides are suggested as alternatives to organophosphorous reagents for the extraction of actinides from high level liquid waste generated during the reprocessing of irradiated fuels. With a view to study the extraction behaviour of these actinides from nitric acid medium, four diamides namely (1) N,N,N′,N′-tetrabutyl undecyl malonamide (TBUDMA), (2) N,N,N′,N′-tetrabutyl tetradecyl malonamide (TBTDMA), (3) N,N′-dimethyl- N,N′-dibutyl undecyl malonamide (DMDBUDMA) and (4) N,N′-dimethyl- N,N′-dibutyl tetradecyl malonamide (DMDBTDMA) were prepared by substitution on the basic skeletons of N,N,N′,N′-tetraalkyl-2-alkyl malonamides. The substituted diamides showed good extractability towards Am, Pu, Np and U into n-dodecane from nitric acid solutions of concentrations ranging from 3 to 8 M except for DMDBUDMA which showed third phase formation beyond 2 M HNO 3. Extraction maxima for Am with TBUDMA and TBTDMA were seen at 6–7 M whereas DMDBTDMA showed maximum extraction at 5 M nitric acid. Am(III) and Pu(IV) extracted as trisolvates whereas U(VI) was extracted as disolvate. Distribution behaviour of fission products using DMDBTDMA was also investigated. DMDBTDMA was found to be a promising alternative to the TRUEX solvent for the actinide partitioning from simulated High Level Waste (HLW).

EXTRACTION BY N,N,N',N-TETRAALKYL -2 ALKYL PROPANE -1,3 DIAMIDES. I. H2O, HNO3and HClO4

ABSTRACT The extracting properties of substituted diamides were investigated. The auto-association of N,N'-dimethyl dibutyl tetradecyl malonamide (DMDBTDMA) : (C4H9(CH3)NCO)2CHC14H29 in benzene and in TPH (aliphatic hydrocarbon) was shown by NMR using mass-action model. The degree of aggregation depends on the diluent, the diamide concentration and the acidity. The extraction of HNO3 and HClO4 was investigated by distribution measurements and IR spectroscopy. HNO3 extraction is explained by the competing formation of four adducts : whose the equilibrium constants for 0,72 mol.l-1 amide in TPH are 0.167, 0.215, 5.19-10-3 and 3.7-10-4, respectively, on a molal scale. HClO4 is extracted by a reaction involving the competing formation of the two adducts . Their equilibrium constants for 0.697 mol.1-1 amide in TPH are 0.649 and 1.71, respectively, on a molal scale. V(C=O) IR absorption shifts indicate that in are linked by hydrogen bonds, whereas in is transferred from one molecule of acid to one C=O of the DM...