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The extraction behavior of Am(III) and Eu(III) from nitric acid medium (0.001 M to 3 M) was studied in a binary solution of N,N-dioctylhydroxy acetamide (DOHyA) and bis(2-ethyhexyl)diglycolamic acid (HDEHDGA) in n-dodecane to evaluate the feasibility of separating Am(III) from Eu(III) present in 3–4 M nitric acid medium. The extraction of Am(III) and Eu(III) was studied as a function of various parameters. The results were compared with the individual extractants in n-dodecane. Synergic extraction of Am(III) and Eu(III) was observed at nitric acid concentrations above 0.5 M and antagonism at lower nitric acid region. The dependence of distribution ratio of Am(III) and Eu(III) on binary extractants was probed by the slope analysis of the extraction data, and the mechanism of Am(III) and Eu(III) extraction was determined at various acidities. The results revealed the possibility of single-cycle separation of Am(III) from Eu(III) with a separation factor ~13.

The bulk extraction of Nd(III) from 4 M nitric acid medium was studied in a solution of N,N-di-octyl-2-hydroxyacetamide (DOHyA) in n-dodecane as a function of γ absorbed dose up to 750 kGy. The average size of reverse micellar aggregates in the irradiated and un-irradiated DOHyA samples after the extraction of Nd(III) was measured by dynamic light scattering (DLS) spectroscopy. The effect of absorbed dose of γ radiation and concentration of Nd(III) in the organic phase on the aggregation behavior of DOHyA was investigated by DLS measurements and ATR-FTIR spectroscopy. The data on irradiated and un-irradiated samples were compared. FT-IR analysis of the irradiated samples of DOHyA showed the formation of degradation products which were mainly identified as hydroxyacetic acid and primary or secondary amines.

A new ammonium-based task-specific ionic liquid, N,N-dioctyl-(4-trihexylammonium)butyramide bis(trifluoromethanesulfonyl)imide ([AmDOA][NTf2]), was synthesized and characterized by elementa...

Diglycolamides (DGAs) are promising reagents for the separation of trivalent actinides and lanthanides from the nitric acid medium. The alkyl group attached to DGAs plays an important role in deciding the extraction and third phase formation behavior of trivalents in DGAs. To understand the role of alkyl group (varied from hexyl to dodecyl) attached to DGA, the extraction behavior of Nd(III) from the nitric acid medium was studied in 0.2 M alkyl DGA in n-dodecane (n-DD). The organic phase obtained after extraction was subjected to dynamic light scattering (DLS) studies to explore the behavior of reverse micelles (or aggregates) formed in the organic phase. The data were compared with the self-aggregation behavior of DGAs in n-DD. The results revealed that the aggregate size and their distribution in n-DD increased with increase in the extraction of nitric acid and Nd(III) in organic phase for all DGAs. However, at certain conditions of loading of HNO3 and Nd(III) the organic phase underwent splitting into...

N , N -dioctyl-2-hydroxyacetamide (DOHyA) in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C 4 mim][NTf 2 ]) was employed for the extraction of actinides from nitric acid medium. The extraction of Pu(IV) was studied as a function of various parameters such as concentration of nitric acid, extractant concentration, temperature, alkyl chain length attached to amidic nitrogen of the extractant etc. The distribution ratio of plutonium(IV) (D Pu(IV) ) obtained in DOHyA/[C 4 mim][NTf 2 ] was compared with that obtained in DOHyA/ n -dodecane ( n -DD). Extraordinary extraction of Pu(IV) was achieved when ionic liquid was employed as a diluent. D Pu(IV) in DOHyA/[C 4 mim][NTf 2 ] decreased marginally with increase in nitric acid concentration up to 3 M nitric acid, and there after the D Pu(IV) remained constant. A significant separation was achieved for Pu(IV) over U(VI) and Am(III) from the employed mixture of actinides at various nitric acid concentrations using DOHyA/[C 4 mim][NTf 2 ]. Stripping of metal ion (Pu(IV)) from the loaded ionic liquid phase was carried out using aqueous soluble complexing agents such as oxalic acid and acetohydroxamic acid.

The aggregation behavior of N,N,N’,N’-tetraoctyldiglycolamide (TODGA) in n-dodecane was studied in the presence of two different phase modifiers, N,N-di-hexyloctanamide (DHOA) and 1-octanol using dynamic light scattering (DLS) spectroscopy. The results were compared with the aggregation behavior of a modifier free extractant system N,N-di-octyl-2-hydroxyacetamide (DOHyA) in n-dodecane. Aggregation studies were done as a function of concentration of nitric acid and Nd (III) ions in the aqueous phase. The size distribution of reverse micellar aggregates revealed different aggregation mechanisms in the presence and absence of phase modifiers. For TODGA-modifier systems, the sizes of reverse micellar aggregates were bigger than DOHyA and among the two phase modifiers studied, use of 1-octanol resulted in the formation of bigger aggregates compared to DHOA. The observations from DLS measurements were co-related with the results from ATR-FTIR spectroscopy for all the three extractant systems. The sizes of reverse micellar aggregates increased with increase in extraction of nitric acid and/or Nd (III) ions and no third phase was visible in all the three systems even under very high loading conditions. The aggregation studies under co-current extraction conditions from fast reactor simulated high level waste solution (FR-SHLLW) showed the formation of smaller reverse micellar aggregates and third phase or crud formation after 3–4 successive contacts for all the three systems.

Tri-n-butylphosphate (TBP) in an ionic liquid (IL) has been proposed as a suitable alternative for the solvent extraction of actinides from nitric acid solutions. This paper reports the detailed investigations on the physicochemical and hydrodynamic properties of the solvent system containing TBP in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTf2]) IL. The properties such as density, viscosity, phase separation time (PST), etc., were measured for irradiated and unirradiated solvent phases composed of TBP, [C4mim][NTf2] and 1.1 mol·L–1 TBP in [C4mim][NTf2]. The results are compared with the values obtained in acid-equilibrated IL phases. ATR–FTIR spectroscopy and dynamic light scattering measurement of the IL phase were employed to characterize the interactions among the IL, TBP and nitric acid medium, and the aggregate size of the adduct formed in the IL phase.

Phase modifiers have been added to the solvent phase to prevent the undesirable third phase formation during the course of solvent extraction. Bis(2-ethylhexyl)phosphoric acid (HDEHP) has been explored as a phase modifier during the extraction of Nd(III) from nitric acid medium in a binary solution of tetra-bis(2-ethylhexyl)diglycolamide (TEHDGA) and HDEHP in n-dodecane (n-DD). To unravel the peculiar role of HDEHP in this binary solution, the reverse micellar aggregates formed in the organic phase upon nitric acid and Nd(III) extraction were probed by Dynamic Light Scattering (DLS) and Fourier Transform Infrared (FTIR) spectroscopy. The aggregate size and its distribution in the organic phase increased with an increase in the concentration of nitric acid and Nd(III) in the aqueous phase. The limiting aggregate size for the formation of a third phase in 0.2 M TEHDGA/n-DD was determined to be ∼30 nm in 1 M nitric acid. The effect of HDEHP concentration on the aggregate size was studied and the concentration of HDEHP needed for preventing third phase formation during the course of Nd(III) extraction from 4 M nitric acid medium was optimized. The results revealed that employment of about 0.25 M HDEHP in 0.2 M TEHDGA/n-DD not only prevented third phase formation during the extraction of trivalent metal ions from nuclear wastes but also facilitated the extraction of trivalents into the binary solution, due to synergism.

N,N-dihexyloctanmide (DHOA) in ionic liquid medium has been proposed for the solvent extraction of actinides from nitric acid solutions. This paper reports the physicochemical and hydrodynamic properties of the solvent system containing N,N-dihexyloctanmide (DHOA) in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTf2]) ionic liquid, for the first time. The properties such as density, viscosity, phase disengagement time etc. were measured for irradiated and unirradiated liquids composed of DHOA, [C4mim][NTf2] and 1.1 M solution of DHOA in [C4mim][NTf2]. The results were compared with the values obtained for the nitric acid equilibrated–organic phases. ATR-FTIR spectroscopy and dynamic light scattering (DLS) measurement of the ionic liquid phase was employed for characterizing interaction between the ionic liquid-DHOA-nitric acid, and the aggregate size of the adduct formed in the solution.

Extraction behavior of Eu(III) from nitric acid medium was studied in a binary solution of tetra bis(2-ethylhexyl)diglycolamide (TEHDGA) and an acidic extractant (HA) present in n -dodecane ( n -DD). The acidic extractants chosen were bis(2-ethylhexyl)phosphoric acid (HDEHP), bis(2-ethylhexyl)phosphonic acid (PC88A) and bis(2,4,4-trimethylpentyl)phosphinic acid (CYANEX-272) whose pK a values were 3.24, 4.51 and 6.37 respectively. The interaction of Eu(III) with TEHDGA and HA at various acidities was studied by Attenuated Total Reflectance (ATR)-Fourier Transform Infrared (FTIR) spectroscopy. The changes in the amidic C O and etheric C O stretching bands of TEHDGA and phosphoryl P O stretching bands of HA occurred upon Eu(III) extraction at various acidities were monitored, and correlated the peak shifts observed in the ATR-FTIR spectrum to the distribution ratio of Eu(III) in the binary solution and pK a value of the acidic extractant.

The trivalent actinide selective neutral extractants such as carbamoylmethylphosphine oxide (CMPO) and bis-(2-ethylhexyl)diglycolamide (TEHDGA) in conjunction with an acidic extractant bis-2-ethylhexylphosphoric acid (HDEHP) have been impregnated in Tulsion ADS 400, and the resultant solvent impregnated resin (SIR) has been evaluated for the radiolytic stability towards gamma radiation. The extraction behavior of Am(III) and the loading behavior of Eu(III) in the SIR was studied as a function of absorbed dose up to 550 kGy, at different nitric acid concentrations in aqueous phase. The extraction isotherm of Eu(III) in various SIRs have been fitted using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) adsorption models. The extraction results and modeling of extraction isotherms obtained at various absorbed dose levels have been reported in this paper.

The extraction behaviour of Am(III) and other metal ions present in the fast reactor simulated high- level liquid waste (FR-SHLLW) was studied using a modifier-free solvent phase composed of N,N-di-octyl-2-hydroxyacetamide (DOHyA) in n-dodecane. Quantitative extraction of Am(III) was achieved with the co-extraction of all lanthanides, Y(III) and Mo(VI) in the first five stages of a 20-stage mixer-settler. During the stripping run with 0.5 M HNO3, Am(III), Ln(III) and Y(III) were quantitatively transferred to the aqueous product in three stages. The other extracted metal ions were retained in organic phase. The results showed that the extraction performance of DOHyA was superior to other amide extractant systems reported in the literature.

Imidazolium bis(2-ethylhexyl)phosphate ionic liquid was anchored on a polystyrene-divinylbenzene (PS-DVB) copolymer and the product (R-Im-DEHP) was studied for the extraction of Am(III) and Eu(III) from dilute nitric acid medium to examine the feasibility using the anchored adsorbent for their mutual separation. The effect of various parameters such as the duration of equilibration, concentration of nitric acid, europium ion, and diethylenetriaminepentaacetic acid (DTPA) in aqueous phase on the distribution coefficient (K d) of Am(III) and Eu(III) was studied. The distribution coefficient of Am(III) and Eu(III) decreased with increase in the concentration of nitric acid. Rapid extraction of metal ions in the initial stages of equilibration followed by the establishment of equilibrium occurred within 4 h. The data on the rate of uptake of Am(III) and Eu(III) were fitted into pseudo-first order and pseudo-second order rate equation. The extraction isotherm was fitted to Langmuir and Freundlich adsorption models and the apparent europium extraction capacity was determined. The mechanism of extraction was elucidated and the conditions needed for efficient separation of Am(III) from Eu(III) was optimized using DTPA. The study indicated the possibility of using R-Im-DEHP for the separation of Eu(III) from Am(III) with high separation factors.

A combination of neutral and acidic extractant has been proposed for the single-cycle separation of trivalent actinides from high-level liquid waste (HLLW). The nature of acidic extractant in the combined solvent formulation plays a profound role in deciding the extraction and stripping of trivalent actinides. Therefore, the extraction behavior of Am(III) in a solution of tetra-bis(2-ethylhexyl)-diglycolamide (TEHDGA) and acidic extractant (HA) was studied from nitric acid medium. The acidic extractants chosen were bis(2-ethylhexyl)phosphoric acid (HDEHP), bis(2-ethylhexyl)phosphonic acid (PC88A) and bis(2,4,4-trimethylpentyl)phosphinic acid (CYANEX-272) whose pKa values were 3.24, 4.51 and 6.37, respectively. The distribution ratio of Am(III) was measured as a function of various parameters such as concentration of nitric acid, TEHDGA, HA etc. The data were compared with those obtained in individual solvent systems namely 0.1 M TEHDGA/n-DD and HA/n-DD. Slope analysis of the extraction data indicated the synergic participation of both TEHDGA and HDEHP in the extraction of Am(III) at all acidities. However, antagonistic effect was observed at lower acidity when TEHDGA was mixed to PC88A or CYANEX-272 present in n-DD. Accordingly, a suitable mechanism has been proposed for the extraction of Am(III) at all acidities using these combined solvent formulation. Studies with fast reactor simulated high level liquid waste indicated that extraction of Am(III) was accompanied by co-extraction of lanthanides and unwanted metal ions such as Zr(IV), Mo(VI), Y(III) and Pd(II). However, addition of trans-1,2-diaminocyclohexane-N,N,N,N′-tetraaceticacid (CyDTA) reduced the extraction of unwanted metal ions. Batch extraction and stripping studies indicated the possibility of using 0.1 M TEHDGA+0.25 M HDEHP in n-dodecane for the single cycle separation of Am(III) from FR-SHLLW.

The imidazolium bis(2-ethylhexyl) phosphate moiety was chemically attached on silica gel by chemical modification. The resulting product ([SG-Im]+ [DEHP]−) was characterized by FT-IR spectroscopy, thermogravimetry and elemental analysis. The sorption behavior of Am(III) and Eu(III) on [SG-Im]+ [DEHP]− was studied from dilute nitric acid medium for the separation of Am(III) and Eu(III) from aqueous waste. The effect of time, concentrations of nitric acid and europium in aqueous phase on the distribution coefficient (K d) was studied. The study indicated the possibility of using modified silica for the separation of Eu(III) from Am(III) with high separation factors (>50 at 0.1 M HNO3).

Uranium oxide (U 3 O 8 ) was dissolved in 1-butyl-3-methylimidazolium chloride (C 4 mimCl) in the presence of small quantity of nitric acid and the uranyl species present in the resultant solution was characterized by UV–Visible, ATR-FTIR and Raman spectroscopy. The electrochemical behaviour of UO 2 2 + present in the resultant solution was studied at glassy carbon electrode by cyclic voltammetry and chronopotentiometry. The diffusion coefficient of UO 2 2 + in C 4 mimCl was determined. The [UO 2 Cl 4 ] 2 − species present in ionic liquid medium, confirmed by the spectroscopic studies, underwent a two electron transfer reduction to UO 2 at the working electrode.