Tetra-2-ethylhexyl Diglycolamide Research Articles

Liquid – Liquid Extraction and Pertraction of Eu(III) from Nitric Acid Medium Using Several Substituted Diglycolamide Extractants

Solvent extraction and supported liquid membrane (SLM) transport properties of Eu(III) from nitric acid feed conditions were investigated using several substituted diglycolamide (DGA) extractants such as N,N,N′N′-tetra-n-octyl diglycolamide (TODGA), N,N,N′N′-tetra(2-ethylhexyl) diglycolamide (T2EHDGA), N,N,N′N′-tetra-n-hexyl diglycolamide (THDGA), N,N,N′N′-tetra-n-pentyl diglycolamide (TPDGA), and N,N,N′N′-tetra-n-decyl diglycolamide (TDDGA). Effects of feed acidity and phase modifier composition on Eu(III) extraction were investigated using the DGAs and the nature of extracted species were ascertained by slope analysis method. The Eu(III) distribution ratio (DEu) values were found to decrease in the presence of iso-decanol. In general, the DEu values decreased with increased alkyl chain length of the DGA. The extracted species contained only 2 extractant molecules when TPDGA and TDDGA were used while for TODGA about four extractant molecules were found to be present in the extracted species. The supported liquid membrane transport of Eu(III) was studied under varying experimental conditions using the five DGA extractants. Transport studies using 0.1 M DGA as the extractant suggested the trend as TDDGA > TODGA > T2EHDGA ∼ THDGA which significantly changed to TPDGA > THDGA > TODGA > TDDGA > T2EHDGA in the presence of 30% iso-decanol as the phase modifier. The permeability coefficient (P) values were also determined with membranes of varying pore sizes.

Separation and purification of 90Sr from PUREX HLLW using N,N,N′,N′-tetra(2-ethylhexyl) diglycolamide

This paper describes a method for the separation and purification of 90Sr from PUREX–HLLW employing solvent extraction and precipitation techniques. 30 % TBP in n-dodecane was used for the removal of residual uranium, plutonium and neptunium from HLLW. Trivalent actinides and lanthanides were subsequently removed using N,N,N’,N’-tetra(2-ethylhexyl) diglycolamide (TEHDGA, 0.20 M in 30 % isodecyl alcohol and n-dodecane). 90Sr was selectively extracted from actinides and lanthanides depleted HLLW using 0.3 M TEHDGA in 5 % isodecyl alcohol and dodecane. Loaded strontium was stripped using 0.01 M HNO3 and further purified by radiochemical precipitation technique after adding Fe and natural strontium as carriers. Based on the experimental results, a flow-sheet was formulated and mCi levels of 90Sr recovered.

Role of alkyl chain branching on aggregation behavior of two symmetrical diglycolamides: Small angle neutron scattering studies

The two long alkyl chain derivatives of diglycolamide (DGA), viz. N,N,N′,N′-tetraoctyl diglycolamide (TODGA) and N,N,N′,N′-tetra(2-ethylhexyl)-diglycolamide (T2EHDGA) have been found promising for actinide partitioning from high-level waste. The solvent extraction studies have suggested the participation of three to four DGA molecules in the extracted complex of trivalent actinides and lanthanides. However, coordination of 3–4 tridentate DGA ligands with trivalent f-elements seems to be unusual due to restricted coordination sites in these metal ions. Nonetheless, the extraction data have been explained in view of the formation of aggregates of these ligands in the organic phase. Small Angle Neutron Scattering (SANS) measurements were carried out to investigate the aggregation behavior of DGA ligands in deuterated n-dodecane. The aggregation of DGA molecules was facilitated by the presence of acid. However, the presence of nitrate ions in the aqueous phase had no significant effect on the aggregation of DGA. Similarly, the presence of metal ions such as Sr(II) or Eu(III) marginally affected the aggregation tendency of DGA molecules. TODGA displayed higher aggregation tendency than that of T2EHDGA. The extraction data of trivalent f-elements were in conformity with the aggregation tendency of the two DGA ligands.

Separation of strontium from the raffinate solution of TEHDGA-actinide partitioning process: Batch extraction and process development

The extractant N,N,N′,N′-tetra-2-ethylhexyl diglycolamide (TEHDGA) has been evaluated for extraction of strontium from the raffinate solution of TEHDGA-actinide partitioning process. Actinide partitioning of HLW using 0.2M TEHDGA+30% isodecyl alcohol/n-dodecane, carried at our unit at engineering scale, selectively separates trivalent ‘f’ group elements from HLW leaving all the elements including strontium in the raffinate. Strontium from the raffinate was extracted using 0.3M TEHDGA+5% isodecyl alcohol/n-dodecane, isodecyl alcohol has been used as a phase modifier whose concentration was optimized to 5% (v/v) to obtain maximum extraction of strontium (D3.1–3.8M=23) without third phase formation in the given extraction conditions. The stoichiometry of the extracted complex was found to depend on initial aqueous nitric acid concentration and obtained as Sr(NO3)2(TEHDGA)2(HNO3)2. Fission products, such as Mo, Pd, and Zr, co-extracted during extraction process were scrubbed with 3.5M nitric acid containing 0.2M oxalic acid and 0.05M HEDTA. Complete stripping of strontium was achieved with 0.01M nitric acid. Quantitative recovery of strontium was obtained in a single contact of extraction, two contacts of scrubbing and two contacts of stripping each at O/A=1.

Liquid–liquid extraction and pertraction behavior of Am(III) and Sr(II) with diglycolamide carrier extractants

Solvent extraction and supported liquid membrane transport properties of Am(III) and Sr(II) from nitric acid medium using several substituted diglycolamides (DGAs) were investigated in detail. The DGAs studied were N,N,N′N′-tetraamyl diglycolamide (TPDGA), N,N,N′N′-tetrahexyl diglycolamide (THDGA), N,N,N′N′-tetraoctyl diglycolamide (TODGA), N,N,N′N′-tetra(2-ethyl hexyl)diglycolamide (T2EHDGA) and N,N,N′N′-tetradecyl diglycolamide (TDDGA). Effects of feed acidity, phase modifier composition, nature of species were investigated for the solvent extraction of the radionuclides using the DGAs. The trend of Am(III) extraction was TPDGA≫THDGA≫TODGA>TDDGA≫T2EHDGA. The slope analysis method for Am(III) extraction has indicated extracted species containing 4 and 3 molecules of the extractant for TODGA and T2EHDGA, respectively and about two molecules of extractant were found to be associated with the other DGAs. When simulated high level waste was used as the feed, the distribution ratio values decreased significantly.Supported liquid membrane transport of the radionuclides was evaluated to understand the effects of feed acidity, membrane pore size and phase modifier concentration for the DGAs. While the trends for Am(III) transport rate were TPDGA∼THDGA∼TDDGA>TODGA>T2EHDGA and usually 2–5h were needed for quantitative transport (>99%), Sr(II) transport was found to be significant in this time scale. The trend for activation energies of transport of Am(III) was found to be TDDGA>THDGA>TPDGA (with 30% iso-decanol)>T2EHDGA>TODGA.

Role of diluent on the separation of 90Y from 90Sr by solvent extraction and supported liquid membrane using T2EHDGA as the extractant

The separation behaviour of (90)Y from (90)Sr was investigated by diluent variation using solvent extraction and supported liquid membrane techniques employing N,N,N',N'-tetra-2-ethylhexyldiglycolamide (T2EHDGA) as the extractant. Both D(Y) (distribution ratio of Y(III)) and S.F. (separation factor) were found to be high in the solvent extraction studies when chloroform was used as the diluent. Subsequent supported liquid membrane (SLM) studies using PTFE flat sheet membranes containing 0.2M T2EHDGA in various diluents indicated the trend of Y transport as xylene>hexone>chloroform>carbon tetrachloride>n-dodecane+30% iso-decanol mixture. However, the Sr(II) transport rates were also high with xylene, hexone, and carbon tetrachloride as the diluents which led us to carry out subsequent studies using chloroform and n-dodecane+30% iso-decanol mixture. Acid variation studies in chloroform system indicated an interesting phenomena of increasing Y(III) transport and decreasing Sr(II) transport with increasing acid concentration. Separation of (90)Y from a mixture of (90)Sr and (90)Y was also attempted.

Uranium(VI) pertraction across a supported liquid membrane containing a branched diglycolamide carrier extractant: Part III: Mass transfer modeling

Solvent extraction and facilitated transport of UO 2 2+ across supported liquid membrane containing N,N,N′,N′-tetra-2-ethylhexyldiglycolamide (T2EHDGA) in n-dodecane as the carrier extractant and 30% iso-decanol as the phase modifier were investigated from nitric acid feed solutions. Extraction constants were comparable to those reported earlier for the U(VI)-TODGA extraction system at 3.0 M HNO 3 feed conditions and consequently, the transport rates were comparable with the two extractants. > 80% U transport was reported in 5 h while using 3 M HNO 3 as the feed and 0.01 M HNO 3 as the receiver phase solution. Mass transport modeling of the facilitated transport of uranyl ion across PTFE supported liquid membranes was done by a developed mathematical model. Diffusion coefficients were calculated using Danesi's model as well as by lag time measurements. The transport was found to be diffusion controlled in the membrane phase and the permeability coefficient was calculated to be (3.20 ± 0.13) × 10 − 4 cm/s for the feed composition of 3 M HNO 3, receiver phase composition of 0.01 M HNO 3 and membrane carrier phase of 0.2 M T2EHDGA in n-dodecane containing 30% iso-decanol while the membrane diffusion coefficient was calculated to be (1.58 ± 0.16) × 10 − 6 cm 2/s.

Hydrodynamic properties for N,N,N′,N′‐tetraalkyl diglycolamides dissolved in n‐dodecane system

AbstractN,N,N′,N′‐tetraoctyl diglycolamide (TODGA) and N,N,N′,N′‐tetra(2‐ethylhexyl) diglycolamide (T2EHDGA) have been identified as promising extractants for actinide partitioning from high‐level nuclear waste. These extractants are proposed to be used along with suitable phase modifiers, viz. N,N‐dihexyl octanamide (DHOA), tri‐n‐butyl phosphate (TBP) and 2‐decanol dissolved in n‐dodecane. Hydrodynamic parameters, viz. density, viscosity and interfacial tension (IFT) are important for optimisation of hydrometallurgical process to ensure that there is no emulsion formation and to achieve desired phase disengagement rate. Densities and viscosities of the two extractants, viz. TODGA and T2EHDGA along with different phase modifiers have been measured over different range of compositions and temperatures (298–333 K). The viscosity data have been used to calculate the activation energy for viscous flow for each composition of solvents. The IFT values have also been measured for different solvent compositions. The viscosity and IFT data of TODGA and T2EHDGA with 2‐decanol as phase modifier appears suitable under hydrometallurgical conditions proposed for actinide partitioning. © 2011 Canadian Society for Chemical Engineering

Studies on the use of N,N,N′,N′-Tetra(2-Ethylhexyl) Diglycolamide (TEHDGA) for Actinide Partitioning II: Investigation on Radiolytic Stability

N,N,N′,N′-tetra(2-ethylhexyl)diglycolamide (TEHDGA) was found to be a promising extractant for actinide partitioning from high-level waste (HLW) (Part I). In order to evaluate the applicability of TEHDGA to the HLW partitioning process, investigations on its radiolytic stability were carried out. The present work deals with the studies on the uptake of americium by γ-irradiated 0.2 M TEHDGA/n-dodecane in the absence and presence of phase modifiers—di(n-hexyl)octanamide (DHOA), isodecanol and n-decanol—against the absorbed dose up to 1 × 106 Gy in the presence of nitric acid at varying concentrations. The addition of phase modifiers suppressed the radiolysis of TEHDGA in n-dodecane and DHOA was found to be the most effective radiolysis suppressor. Investigations were also carried out on the degradation of neat TEHDGA by γ-irradiation, and it was attempted to isolate and identify its degradation products by instrumental analysis. The radiolysis study showed that the degradation products were formed by the cleavage of the –C-N bond, to eliminate an ethylhexyl group, and the bond adjacent to the ether bond. The results obtained for TEHDGA radiolysis were compared with that of its straight-chain isomer TODGA, and TEHDGA was observed to be more resistant to radiation than TODGA. The changes in the physico-chemical properties of γ-irradiated TEHDGA against the absorbed dose were also investigated.

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.

Studies on the radiolytic stability of N,N,N′,N′-tetra-2-ethylhexyl diglycolamide in n-dodecane solution containing different phase modifiers

The radiolytic stability of a branched diglycolamide extractant, namely N,N,N′,N′-tetra-2-ethylhexyl diglycolamide (T2EHDGA) dissolved in n-dodecane containing several phase modifiers, viz. N,N-dihexyloctanamide (DHOA), tri-n-butyl phosphate (TBP), 1-decanol and iso-decanol has been investigated. The distribution ratio of Am(III) decreased with increased radiation dose studied up to 1000 kGy. Nevertheless, all the composition of extractants showed satisfactory results up to 500 kGy, beyond which the extractants degraded drastically. The stripping behaviour of Am(III) with 0.2 M HNO3 was found to be unaffected even with the ligand solution irradiated up to 1000 kGy. Extraction of fission product and structural elements was also investigated using the irradiated solvents and was found to be not significantly affected with increasing absorbed dose with the exception of Mo which showed sharp rise in the distribution coefficient values. Loading of Nd in the organic phase decreased with the irradiated solvent due to degradation of the carrier. The effect of the absorbed dose on physical parameters such as density, viscosity and interfacial tension of the solvents has also been investigated.

Preferential extraction of 90Y from 90Sr using N,N,N′,N′-tetra-2-ethylhexyl diglycolamide (T2EHDGA) as the extractant

N,N,N′,N′-tetra-2-ethylhexyldiglycolamide (T2EHDGA) has been used for the preferential extraction of 90Y from its mixture with 90Sr from HNO3 as well as HCl medium. The separation efficiencies have been found out under varying experimental conditions. The extracted species were determined from T2EHDGA concentration variation experiments carried out at 3 M nitric acid as well as HCl and were found out to be Y(X3)3·3(TEHDGA)(o) for both the extraction systems, where X = NO3− and Cl−, respectively. Comparison of the T2EHDGA and TODGA based separation methods is also made. In order to avoid third phase formation, iso-decanol has been used as the modifier in all the studies. The modifier content was optimized to 30% for 4 M HCl and 20% for 6 M HNO3 as the feed aqueous phases. Separation schemes were developed for the separation of carrier free 90Y and the purity was checked by the half-life measurement method.

Demonstration of T2EHDGA Based Process for Actinide Partitioning Part II: Counter-Current Extraction Studies

Counter-current mixer-settler studies for actinide partitioning were carried using N,N,N′,N′-tetra-2-ethylhexyl diglycolamide (T2EHDGA) as the extractant. The feed solution was Simulated High Level Waste of Pressurized Heavy Water Reactor (PHWR-SHLW) origin spiked with 241Am, 244Cm, 152Eu, 137Cs, 85,89Sr, 59Fe, 106Ru, 109Pd, 95Zr, and 99Mo tracers. The organic stream was 0.1 M T2EHDGA + 5% isodecanol in n-dodecane. Extraction, scrubbing, and stripping experiments were performed by maintaining an organic to aqueous phase ratio of 1. More than 99.9% of the trivalent actinides and lanthanides were extracted in four stages, and the decontamination factors (D.F.) values were >103 obtained for most fission products. The co-extraction of Zr and Pd was prevented by the addition of oxalic acid and N-(2-hydroxyethyl)-ethylenediamine-triacetic acid (HEDTA) into the feed solution. However, ∼20% Ru and 10% Mo was extracted into the organic phase, which was successfully scrubbed using a mixture of 0.2 M oxalic acid and 0.1 M HEDTA in 5 M HNO3. Finally, the extracted actinides and lanthanides were quantitatively stripped with 0.2 M HNO3. Raffinate of the extraction cycle was found to be free from any alpha activity.

Development of T2EHDGA Based Process for Actinide Partitioning. Part I: Batch Studies for Process Optimization

N,N,N′,N′-tetra-2-ethylhexyl diglycolamide (T2EHDGA) has been used for the extraction of actinides, lanthanides, fission products, and structural elements from Pressurized Heavy Water Reactor High Level Waste (PHWR-HLW). In view of third-phase formation under loading conditions, iso-decanol, tri-n-butyl phosphate (TBP), and N,N-di-n-hexyl octanamide (DHOA) were evaluated as the phase modifiers along with T2EHDGA. The loading of lanthanides (e.g. Nd(III), used as surrogate for trivalent minor actinides, Am(III) and Cm(III) and rare earth elements) in the organic phase sharply increased with the addition of iso-decanol as compared to other modifiers (TBP and DHOA). A minimum concentration of phase modifiers needed to avoid third-phase formation for 0.1 M T2EHDGA was 5% iso-decanol, 20% TBP or 20% DHOA. The most promising system, viz. 0.1 M T2EHDGA and 5% (v/v) iso-decanol was evaluated as extractant for actinide partitioning. The distribution behavior of various metal ions, viz. Am, Pu, U, Eu, Sr, Pd, Cs, Tc, Fe, and Mo has been studied from nitric acid as well as from synthetic PHWR-HLW using the optimized organic phase. Extraction of Am (tracer) from synthetic PHWR-HLW suggested a quantitative recovery of minor actinides in four contacts, while stripping (with 0.01 M HNO3) was quantitative in two contacts at O/A = 1. The testing of the optimized extraction system in mixer-settlers with simulated HLW is in progress.

Comparative evaluation of two substituted diglycolamide extractants for ‘actinide partitioning’

Extraction behaviour of actinides, lanthanides, fission products and structural elements has been studied with the two diglycolamide extractants, namely N,N,N 0 ,N 0 - tetra-2-ethylhexyl diglycolamide (T2EHDGA) and N,N,N 0 ,N 0 - tetraoctyl diglycolamide (TODGA). The acid extraction studies suggested that T2EHDGA (KH: 1.8) is less basic as compared to its linear homologue, TODGA (KH: 4.1). The distribution ratio of Am(III) by 0.1 M diglycolamides fol- lowed the order: TODGA ( T2EHDGA. The number of ligand molecules present in the stoichiometry of the extracted species of Am(III) was found to be three and four for T2EHDGA and TODGA, respectively. Thermodynam- ics studies suggested that the extraction of Am(III) by both the extractants is exothermic in nature. The radiolytic sta- bility of TODGA and T2EHDGA solutions in n-dodecane has been investigated. Due to lower distribution ratio of Am by T2EHDGA, 0.2 M of its solution has been used as compared to 0.1 M solution of TODGA. The distribution behaviour of various metal ions, viz. Am, Nd, Fe, Mo, Cr, Sr and Cs has been studied from nitric acid as well as from simulated high level waste solution.

Studies on the Use of N,N,N´,N´-Tetra(2-ethylhexyl) Diglycolamide (TEHDGA) for Actinide Partitioning. I: Investigation on Third-Phase Formation and Extraction Behavior

Diglycolamides have emerged as an interesting class of extractants for actinide partitioning from high-level waste (HLW). N,N,N´,N´-tetraoctyl diglycolamide (TODGA) has been extensively studied for lanthanide-actinide co-extraction behavior. The present work deals with a branched isomer of TODGA, that is, N,N,N´,N´-tetra(2-ethylhexyl) diglycolamide (TEHDGA). TEHDGA was studied for the extraction of 241Am and third-phase formation. The effect of using different phase modifiers on the prevention of the formation of a third phase during nitric acid extraction by TEHDGA along with the acid uptake behavior by TEHDGA in the presence of the modifiers was studied. The modifiers used for this purpose were di(n-hexyl)octanamide (DHOA), isodecanol, and n-decanol. The effect of the modifiers on the uptake of 241Am as a function of acid concentration and as a function of modifier concentration was also examined. DHOA was found to be a suitable modifier, in spite of its high acid uptake. The uptake of lanthanides Ce, La, Eu, Gd, and Nd and elements such as Fe, Ni, Mn, Mo, Ru, Sr, and Cs with DHOA-modified TEHDGA–n-dodecane solvent systems were investigated. The results obtained indicated that, while DHOA-modified TEHDGA/n-dodecane extracted lanthanides and actinides, it did not show any significant uptake of other elements. Thus, the TEHDGA-DHOA/n-dodecane solvent system can be used effectively for the partitioning of lanthanides and actinides from HLW.

Facilitated transport of Am(III) through a flat-sheet supported liquid membrane (FSSLM) containing tetra(2-ethyl hexyl) diglycolamide (TEHDGA) as carrier

Facilitated transport of Am(III) in nitric acid medium using tetra(2-ethyl hexyl) diglycolamide (TEHDGA) in n-dodecane as carrier was studied. It was aimed at finding out the physico-chemical model for the transport of Am(III) using TEHDGA/ n-dodecane as carrier under various experimental parameters like feed acidity, carrier concentration, varying strippant, varying membrane pore size, etc. The feed acidity and carrier concentrations were varied from 1 M to 6 M HNO 3 and 0.1 M to 0.3 M TEHDGA/ n-dodecane, respectively. The transport of Am(III) increased with increase in feed acidity and carrier concentration reaching maximum at 3 M HNO 3 and 0.2 M TEHDGA/ n-dodecane, respectively. Several stripping agents were tested and 0.1 M HNO 3 was found to be the most suitable stripping agent for this system. Almost quantitative transport of Am(III) was observed at about 180 min with feed acidity of 3 M HNO 3, 0.1 M HNO 3 as strippant and 0.2 M TEHDGA/ n-dodecane as carrier. The pore size of the membrane support was varied from 0.20 μm to 5 μm and the permeation coefficient increased with increase in pore size up to 0.45 μm (2.43 × 10 −3 cm/s), and then decreased with further increase in pore size. The plot between permeation coefficient vs. (membrane thickness) −1 was linear which showed that the Am(III) transport was membrane diffusion limited. The membrane diffusion coefficient calculated from the graph was found to be 1.27 × 10 −6 cm 2/s and its theoretical value was 1.22 × 10 −6 cm 2/s. The stability of the carrier against leaching out of the membrane support as well as the integrity of membrane support was studied over a period of 30 days and was found to be satisfactory within the studied time period.

Process Development for Bulk Separation of Trivalent Actinides and Lanthanides from Radioactive High-Level Liquid Waste

In-house R&D studies have resulted in the development of processes for the bulk separation of trivalent actinides and lanthanides from radioactive high-level liquid waste. Synthesis of solvents, namely, n-octyl (phenyl)-N,N-di-isobutyl carbamoyl methyl phosphine oxide and diglycolamide-based tetra (2-ethylhexyl) diglycolamide (TEHDGA), at the required purity has been carried out, and a suitable process for their respective use in actual application has been developed. Inactive scale engineering runs comprised of simultaneous extraction and stripping operations were carried out to establish the process on an engineering scale, including reuse of the solvent system. The composition of surrogate high-level waste (HLW) used at engineering-scale studies corresponds to first-cycle raffinate from reprocessing of long-cooled pressurized heavy water reactor fuel with a burnup of 6500 MWd/tonne. Since trivalent lanthanides and actinides exhibits similar extraction behavior at higher acidity, cerium and lanthanum were only used in making surrogate HLW to represent all the trivalent lanthanides and actinides. Indigenously developed mixer-settlers using a passive system of mixing were used for these runs. Over a period of ˜10 h, ˜300 l of surrogate HLW solutions were contacted with solvent. The results of such repeated trials have shown near-total removal of cerium and lanthanum (>99.8% and 97%, respectively) at aqueous-to-organic ratio of 2.5:1 for a TEHDGA system. As the distribution coefficient values for trivalent actinide (241Am) are found to be significantly higher than those for trivalent lanthanides for both of the solvent systems under consideration, it can be inferred that separation of trivalent actinides along with lanthanides could be feasible using these solvent systems.

ICONE15-10193 Trivalent actinide-lanthanide separation with diglycolamide and a novel aza-amide based extractant

New solvent systems have been developed for the bulk separation of trivalent actinides and lanthanides from radioactive high-level liquid waste and their separation from each other. Synthesis of amidic based solvents namely Tetra (2-ethylhexyl) diglycolamide (TEHDGA) for bulk separation and N,N,N',N'-Tetra(2-ethyl hexyl) 3,6-(N'',N'''dibutyl) Diaza-Octane 1,8 diamide (abbreviated as Diaza Diamide DADA) for group separation, at the required purity have been carried out and suitable process for their respective use in actual applications have been developed. For bulk separation of trivalent actinides and lanthanides, inactive scale engineering runs comprising of simultaneous extraction and stripping operations were carried out to establish the process on an engineering scale including reuse of the solvent system. The composition of surrogate high level waste (HLW) used at engineering scale studies corresponds to first cycle raffinate from reprocessing of long cooled Pressurized Heavy Water Reactor(PHWR) fuel with a burn-up of 6,500 MWd/t. Since trivalent lanthanides and actinides exhibits similar extraction behaviour at higher acidity cerium and lanthanum were only used in making surrogate HLW to represent all the trivalent lanthanides and actinides. In-house developed mixer settlers using passive system of mixing were used for these runs. About 300L of surrogate HLW solutions were contacted with solvent over a period of about 10 hours. The results of such repeated trials have shown near total removal of cerium & lanthanum (>99.8 % & 97 % respectively) at A:O ratio 2.5:1 for TEHDGA system. As the distribution coefficient values for trivalent actinide (^<241>Am) is found to be significantly higher than that for trivalent lanthanides, therefore, it is inferred that separation of trivalent actinides along with lanthanides could be feasible using TEHDGA solvent systems. The stripped product of TEHDGA solvent system was spiked with ^<241>Am and ^<152-154>Eu for studies on group separation of trivalent actinide from lanthanides at laboratory scale using DADA. The solvent system constituted as 0.05M DADA + 10% TBP/n-dodecane, has shown a maximum separation factor of 〜30(D_<Am>/D_<La,Ce>) and 〜5.0 (D_<Am>/D_<Eu>) at pH between 2.5 to 3.0. Complete stripping was achieved at 0.5M nitric acid.