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The radiolytic stability of aqueous solutions containing two different bis-1,2,4-triazines was studied under static gamma irradiation. Sulphophenyl derivatives of bis-1,2,4- triazinyl pyridine (SO3-Ph-BTP) and bis-1,2,4-triazinylbipyridine (SO3-Ph-BTBP) were dissolved in 0.1 M and 1 M HNO3 solutions and the impact of gamma irradiation was assessed by the measurement of distribution ratios of Am(III) and Eu(III) using irradiated samples. The results were compared for two different organic solvents containing N,N,N’,N’-tetraoctyldiglycolamide (TODGA) or N,N-didodecyl-N’,N’-dioctyldiglycolamide (D3DODGA). The separation efficiency of all the systems remained unchanged when the absorbed dose was 100 kGy, and gradually decreased at 200 kGy and 500 kGy. The radiolytic degradation was more apparent for SO3-Ph-BTBP in comparison to SO3-Ph-BTP at higher acidity. The degradation of sulphonate groups in the molecules was evidenced in ATR-FTIR spectral studies.

The organic phase containing tetra(2-ethylhexy)diglycolamide (TEHDGA) and n-dodecane (n-DD) was irradiated to various absorbed dose levels in a 60Co gamma irradiation chamber. The organic phase subjected to irradiation was classified in to four different categories. The extraction behavior of Nd(III) from nitric acid was studied in the degraded solution of 0.2 M TEHDGA/n-DD and the reverse micellar aggregation behavior of the extracted phase was probed by dynamic light scattering technique and ATR-FTIR spectroscopy. The results revealed that the concentration of TEHDGA decreased upon irradiation and minimized the aggregation in organic phase. The presence of n-DD along with TEHDGA during irradiation enhanced the degradation of TEHDGA, due to sensitization effect. In contrast to the assumption of deteriorating effect of gamma radiation on organic phases, the study showed that the radiolytic degradation of TEHDGA/n-dodecane minimized the aggregation and threw the third phase formation limit of Nd(III) in aqueous phase to higher values.

A customized single-stage cylindrical combined air lift mixer-settler (C-CALMIX) device has been developed and its performance was evaluated by studying the extraction behavior of U(VI) in a solution of 1.1 M tri-n-butyl phosphate (TBP) in n–dodecane (n-DD) from 4 M nitric acid medium, at 298 K. The extraction of U(VI) was studied as a function of process parameters of the C-CALMIX such as flow-rate of organic and aqueous phases, ratio of organic to aqueous flow-rates, air flow-rate etc., that are amenable for variation. The distribution ratio of U(VI) obtained under dynamic conditions in a C-CALMIX was compared with those obtained in a batch equilibrium mode. The process parameters were optimized to obtain high distribution ratio of U(VI) in C-CALMIX, comparable to that obtained at batch equilibrium mode without compromising the throughput of C-CALMIX. The stripping behavior of U(VI) from the loaded organic phase was studied using 0.01 M nitric acid. The results are reported in this paper.

Long chain monoamide extractants, N,N-di-decyloctanamide(DDOA), N,N-di-hexyldecanamide(DHDA), N,N-di-2-ethylhexyloctanamide(D2EHOA) and N,N-dihexyl-2-ethylhexanamide(DH2EHA) were synthesized and studied for the recovery of U(VI), Pu(IV) and Zr(IV) from a simulated dissolver solution of un-irradiated U–Zr metallic fuel. The results were compared with the results of N,N-dihexyloctanamide(DHOA) and tri-n-butylphosphate(TBP) under similar conditions. Solvent extraction studies were carried out for comparing the extraction behavior of U(VI), Pu(IV) and Zr(IV) in monoamide extractants with TBP system. The influence of length and branching of alkyl chains on either side of the amidic group on the extraction efficiency, third phase behaviour and metal ion selectivity in long chain monoamides has been discussed based on the results of above studies.

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.

Zirconium was identified as a troublesome fission product interfering with the separation of trivalent actinides from high-level liquid waste (HLLW) solution. Since zirconium was used as a fuel component in metallic fuels, the amount of Zr(IV) present in HLLW arising from reprocessing of metallic fuel was nearly ten times higher than the conventional HLLW solutions. In the present study, the diglycolamide extractants proposed for the separation of trivalent actinides from HLLW were employed for the extraction of metal ions from nitric acid medium and fast reactor simulated high level liquid waste (FR-SHLLW) having the Zr(IV) concentrations varied from 0.006 M to 0.09 M. Dynamic light scattering study was performed on the organic phase obtained after extraction of zirconium to analyze the aggregation of extractants. The solvent system consisting of 0.1 M TODGA (N,N,N’,N’-tetraoctyldiglycolamide) along with 0.25 M HDEHP (bis(-2-ethylhexyl)phosphoric acid) in n-dodecane showed minimal aggregation tendency and higher loading capacity of Zr(IV) and was selected for further extraction of trivalent metal ions from FR-SHLLW. To minimize the extraction of Zr(IV) in organic phase, the effect of aqueous soluble complexing agent namely trans-1,2-diaminocyclo-hexane-N,N,N’N’-tetraaceticacid (CyDTA) was also studied during the extraction of trivalent lanthanides.

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.

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).

Aliquat-336-based strongly hydrophobic ionic liquid, tri-n-octylmethylammonium diglycolamate ([A336]+[DGA]−), was prepared and impregnated in Amberlite XAD-7 (abbreviated as [A336]+[DGA]−/XAD-7) for studying the extraction behavior of Am(III) and Eu(III) from nitric acid medium. The distribution ratio of Am(III) and Eu(III) in [A336]+[DGA]−/XAD-7 decreased with an increase in the concentration of nitric acid and the mechanism of trivalent metal ion extraction in the resin phase was elucidated. The uptake of Am(III) and Eu(III) in [A336]+[DGA]−/XAD-7 followed a second order and from the Langmuir adsorption model the apparent europium extraction capacity was determined. The conditions needed for efficient separation of Am(III) from Eu(III) was optimized.

The homologs of N,N-di-alkyl-2-methoxyacetamides (DAMeOA) having three different alkyl chains varying from hexyl to decyl (C6, C8 and C10) were synthesized and characterized by NMR and IR spectral analyses. Extraction behavior of U(VI) and Pu(IV) from nitric acid medium in a solution of 0.5 M of DAMeOA in n-dodecane (n-DD) was studied and the results were compared with those obtained using N,N-di-hexyloctanamide (DHOA) in n-dodecane. The effect of various parameters on the distribution ratio of U(VI) and Pu(IV) in DAMeOA was studied. The extraction of nitric acid increased with decrease in chain length of alkyl group attached to amidic nitrogen atom of DAMeOA and the conditional nitric acid extraction constant was determined. The extraction of nitric acid in DAMeOA/n-DD resulted in the formation of third phase in organic phase and the third phase occurred early with DAMeOA having smaller alkyl chain length. In contrast to this, the distribution ratio (D) of U(VI) and Pu(IV) in DAMeOA/n-DD increased with increase in the concentration of nitric acid and with increase in the chain length of alkyl group attached to amidic nitrogen atom of DAMeOA. The stoichiometry of the metal – solvate was determined from the slope of extraction data. Quantitative recovery of uranium and plutonium from the loaded organic phase was achieved using dilute nitric acid.

Diglycolic acid modified zirconium phosphate (ZrP-DGA) was prepared and studied for the extraction of Am(III) and Eu(III) from dilute nitric acid medium. The distribution coefficient (Kd, mL·g−1) of Am(III) and Eu(III) was measured as a function of time, pH and concentration of Eu(III) ion etc. The Kd of Am(III) and Eu(III) increased with increase of pH, reached a maximum value of distribution coefficient at pH 1.5 – 2, followed by decrease in Kd values. Rapid extraction of Am(III) and Eu(III) in ZrP-DGA was observed followed by the establishment of equilibrium occurred in 100 min. Kinetics of extraction was fitted in to pseudo second order rate equation. The amount of Eu(III) loaded in ZrP-DGA increased with increase in the concentration of Eu(III) ion in aqueous phase and the isotherm was fitted in to Langmuir and Freundlich adsorption models. The extraction of Am(III) in ZrP-DGA was higher as compared to Eu(III) and the interference of Eu(III) on the extraction of Am(III) was studied. The distribution coefficient of some lanthanides in ZrP-DGA was measured and the Kd of lanthanides increased across the lanthanide series. The extracted trivalent metal ions were recovered in three contacts of loaded ZrP-DGA with 0.5 M nitric acid.

The radiation stability of N,N-di-alkyl-2-hydroxyacetamide derivatives having alkyl side chain varying from hexyl to decyl was studied as a function of absorbed dose of gamma irradiation up to 700 kGy. The samples were irradiated as neat, and as 0.2 M solutions in n-dodecane in the presence and absence of 4 M nitric acid. The radiolytic degradation of the compounds were assessed by the measurement of distribution ratio of Am(III) (DAm(III)) and also by the measurement of hydrodynamic properties such as density, viscosity and phase disengagement time.

The limit of reverse micellar aggregation of amphiphilic ligands in n-dodecane medium, known as the third phase formation, is an undesirable event during the course of solvent extraction. The tetraalkyl diglycolamide (DGA) in n-dodecane (n-DD) is a promising solvent medium for the extraction of trivalent actinides from high-level nuclear waste, but it is susceptible to third phase formation. The DGAs in n-dodecane medium undergo a number of chemical transformations in organic phase, known as the radiolytic degradation products, when it was contacted with nuclear waste. While the effect of radiolytic degradation products on the solvent extraction behaviour of actinides was reasonably understood, the third phase formation and reverse micellar aggregation behaviour of the radiolytically degraded DGAs/n-DD has been not explored so far and unfamiliar to the solvent extraction community. To unravel the effect of radiolytic degradation on the aggregation behaviour(third phase formation) of DGAs in n-DD, the following categories of liquids comprising of (1) 0.2 M solution of tetra(2-ethylhexyl)diglycolamide (TEHDGA) present in n-DD, (2) TEHDGA alone, (3) n-dodecane alone, and (4) 0.2 M TEHDGA/n-DD in the presence of extracted nitric acid, were irradiated to a specified absorbed dose levels (10 kGy to 500 kGy) in a 60Co gamma irradiator. The irradiated liquids were made to a solution of 0.2 M TEHDGA in n-dodecane, if required, and the extraction behaviour of nitric acid in the irradiated organic phase was studied. The organic phase obtained after extraction was subjected to dynamic light scattering studies to explore the aggregation behaviour of TEHDGA in organic phase and compared with those obtained before extraction and irradiation. The results revealed that the formation of polar degradation products upon irradiation minimized the aggregation, and the production of higher homologs of n-paraffins enhanced aggregation. In reality, the formation of nitration and other polar radiolytic degradation products in organic phase, confirmed by FTIR spectroscopy, minimized the aggregation and therefore prevented the third phase formation to a significant extent in the present system.

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

Processing of uranium ore for the production of reactor-grade uranium results in the generation of large amount of aqueous waste containing small quantities of uranium, but higher than the guideline value (15 μg L−1) recommended by World Health Organization (WHO). The presence of uranium in aqueous waste poses several hazards and environmental issues due to the radioactive nature and migration behavior of uranium in the geosphere. In order to remove uranium (VI) from aqueous waste, the diethylenetriamine modified high capacity magnetic iron oxide adsorbent, abbreviated as Fe-DETA, was prepared and studied for the extraction of uranium from aqueous solutions. The Fe-DETA was characterized by X-ray diffraction, thermal analysis, infrared and Raman spectroscopy, and scanning electron microscopy. Significantly high amount (2 mmol g−1) of diethylenetriamine functional group (DETA) was anchored on magnetic iron oxide particles. The extraction of U(VI) from aqueous phase was studied as a function of pH of the aqueous phase, duration of the contact between Fe-DETA and aqueous phase, concentration of U(VI) in aqueous solution etc. The data on the rate of extraction of U(VI) in Fe-DETA was fitted into the first order and second order rate equations. The apparent uranium extraction capacity on Fe-DETA was determined to be 236 mg g−1, which correspond to the formation of 1:2 complex of U(VI) to diethylenetriamine ligand in Fe-DETA phase. The loaded U(VI) in Fe-DETA was quantitatively recovered using dilute Na2CO3 solution, and the recovered Fe-DETA was recycled for further extraction of U(VI), without any change in the apparent U(VI) extraction capacity.

Piperidinium nitrate (Pip − NO3) and pyrrolidinium nitrate (Pyr − NO3) functional groups were anchored on a poly(styrene-divinylbenzene) matrix and evaluated the resultant anion exchange resin for the extraction of plutonium from nitric acid medium. The distribution coefficient (K d, mL/g) of Pu(IV) in these resins increased with the concentration of nitric acid, reaching a maximum K d at 7 M nitric acid, followed by decrease. The extraction of Pu(IV) increased with the duration of equilibration followed by the establishment of equilibrium, occurred within four hours of equilibration. The kinetic data were fitted with pseudo-first order and pseudo-second order rate equations. The apparent plutonium exchange capacity was determined to be ∼256 mg/g for Pip − NO3 resin and 285 mg/g for Pyr − NO3 resin at 7 M nitric acid. The radiolytic degradation of Pip − NO3 and Pyr − NO3 in presence of nitric acid (7 M) was studied upto a dose of 200 KGy and the results are reported in this paper.

The alkyl derivatives of N,N,-dialkyl-2-hydroxyacetamide (DAHyA), namely, N,N,-dihexyl-2-hydroxyacetamide (DHHyA), N,N,-dioctyl-2-hydroxyacetamide (DOHyA), N,N,-didecyl-2-hydroxyacetamide (DDHyA), were synthesized and characterized by FT-IR, and NMR spectroscopy. The extraction behaviour of Am(III) in a solution of DAHyA in n-dodecane was studied as a function of various parameters to evaluate the feasibility of using DAHyA for partitioning of trivalent actinides from high-level liquid waste (HLLW). The distribution ratio of Am(III) (D Am(III)) in 0.1 M DAHyA/n-DD increased from 10−4 to > 200 with increase in nitric acid concentration from 1 M to 6 M. A D Am(III) value 10–70 was obtained in a nitric acid concentration range from 3–4 M. The extraction of Am(III) in 0.1 M DAHyA/n-dodecane decreased in the order DHHyA > DOHyA > DDHyA. The third-phase formation behaviour of nitric acid and neodymium (III) in 0.2 M DAHyA/n-dodecane was studied. Near stoichiometric amount of neodymium (III) can be loaded in octyl and decyl derivatives without any third-phase formation from 3–4 M nitric acid medium. Unlike other extractants, the loaded trivalent metal ion in DAHyA can be recovered even with 1 M nitric acid. Therefore, the study revealed that N,N,-dialkyl-2-hydroxyacetamides are promising candidates for partitioning the trivalent actinides from HLLW.

A novel 2-oxy-N,N-dioctylacetamide anchored on Merrifield resin was synthesized and characterized by elemental analysis, TG-DTA and IR spectroscopy, for the first time. The extraction behavior of Am(III) and Eu(III) from nitric acid medium in the dioctylacetamide anchored resin (R-DOA) was studied as a function of various parameters such as duration of equilibration, concentration of nitric acid and sodium nitrate etc. The distribution coefficient (K d) of Am(III) and Eu(III) in R-DOA increased with increase in concentration of nitric acid. The K d values reached a maximum at 3–4 M nitric acid concentration in both cases, followed by decrease in K d values. Rapid extraction of Am(III) and Eu(III) from nitric acid medium was observed in the initial stages of equilibration followed by the establishment of equilibrium occurred within 60 min. The extraction data was fitted in to the first order rate equation. The recovery of Am(III) and Eu(III) from the loaded organic phase was studied using dilute nitric acid. The results revealed that 2-oxyacetamide functionalized resin is the promising candidate for the separation of trivalent actinides and lanthanides from nitric acid medium.

The extraction and stripping behavior of various metal ions present in the fast reactor simulated high-level liquid waste (FR-SHLLW) was studied using a solvent phase composed of a neutral extractant, N,N,-didodecyl-N′,N′-dioctyl-3-oxapentane-1,5-diamide (D3DODGA) and an acidic extractant, di-2-ethylhexyl diglycolamic acid (HDEHDGA) in n-dodecane (n-DD). The third phase formation behavior of the solvent formulation D3DODGA + HDEHDGA/n-DD, was studied when it was contacted with FR-SHLLW, and the concentration of neutral and acidic extractant needed to avoid the third phase formation was optimized. The distribution ratio of various metal ions present in FR-SHLLW was measured in a solution of 0.1 M D3DODGA + 0.2 M HDEHDGA/n-DD. The extraction of Am(III) was accompanied by the co-extraction of lanthanides and unwanted metal ions such as Zr(IV), Y(III), and Pd(II). A procedure was developed to minimize the extraction of unwanted metal ions by using aqueous soluble complexing agents in FR-SHLLW. Based on those results, the counter-current mixer-settler run was performed in a 20-stage mixer-settler. Quantitative extraction of Am(III), Ln(III), Y(III), and Sr(II) in 0.1 M D3DODGA + 0.2 M HDEHDGA/n-DD was observed. The recovery of Am(III) from the loaded organic phase was carried out by the optimized aqueous formulation composed of 0.01 M diethylenetriaminepentaacetic acid (DTPA) + 0.5 M citric acid (CA) at pH 1.5. The stripping of Am(III) was accompanied by co-stripping of some early lanthanides. However the later lanthanides (Eu(III) and beyond) were not back extracted to Am(III) product. Therefore, the studies foresee the possibility of intra-lanthanides as well as lanthanide-actinide separation in a single-processing cycle.

The radiation stability of an unsymmetrical diglycolamide, di-2-ethylhexyl-di-octyl diglycolamide (DEHDODGA) has been evaluated under various process conditions. The influence of diluent (n-dodecane), phase modifier (N,N-dihexyl octanamide, DHOA), and nitric acid on the radiolysis of DEHDODGA was investigated. The distribution ratio (D) of Am(III), Eu(III), and Sr(II) in the irradiated solvent was determined as a function of absorbed dose of γ-radiation. The distribution ratios decreased with increase of absorbed dose, indicating the radiolytic degradation of DEHDODGA with increase of absorbed dose. The stripping behavior of Am(III) from the degraded organic phase was studied. Quantitative back extraction of trivalent metal ions from the irradiated organic phase was achieved in a single contact using the stripping formulation composed of dilute nitric acid and citric acid. Our studies indicated the robust nature of DEHDODGA with respect to radiolysis, and innocuous nature of degradation products.

A solid phase adsorbent containing amidic carboxylic acid functional group on the surface of the silica gel was prepared by organo-surface modification reactions and characterized the product, Si-SUC, by FT-IR, Raman, thermogravimetry, X-ray diffraction, SEM-EDX and pH titration techniques. The extraction behaviour of U(VI) from aqueous solution was studied as a function of various parameters such as the aqueous phase pH, duration of equilibration, presence of interfering ions and concentration of U(VI) in aqueous phase to evaluate the feasibility using Si-SUC for the recovery of U(VI) from sea water. The kinetic data on the extraction of U(VI) was fitted into second order rate equation, and the U(VI) extraction isotherm was fitted using Langmuir, Freundlich, Dubinin- Radushkevich and Temkin adsorption models. The performance of Si-SUC was evaluated under dynamic conditions by following a break-through behaviour of U(VI) in the column study. The effect of flow-rate and concentration of U(VI) in the feed solution, on the break-through behaviour of U(VI) was studied and fitted the breakthrough curve using Thomas model.

Diethylenetriamine (DETA) moiety was chemically anchored on polystyrene-divinylbenzene (PS-DVB) co-polymer, and the resultant resin (PS-DETA) was studied for the extraction of uranium from aqueous solution. The extraction behavior of U(VI) was studied in PS-DETA a function of duration of equilibration, pH of the feed solution, concentration of U(VI), CO 3 2 − , Fe2＋, Co 2 + and Ni 2 + ions. The rate of extraction of uranium in PS-DETA was fitted into pseudo-first order and pseudo-second order rate equations. The extraction isotherm of uranium was fitted to Langmuir adsorption model. Recycling option of the resin PS-DETA was studied by subjecting the resin to repeated extraction and back-extraction of uranium. The performance of PS-DETA under the dynamic condition was evaluated by following the breakthrough curve of uranium. The extracted uranium was quantitatively recovered by using dilute nitric acid.

The radiolytic degradation of N,N-di-dodecyl-N′,N′-di-2-ethylhexyl-3-oxapentane-1,5-diamide (D3DEHDGA) was studied at various absorbed doses of γ-radiation. The degradation was assessed by measuring the variation in the extraction behavior of Am(III) in irradiated solvent systems composed of neat D3DEHDGA or 0.1 M D3DEHDGA/n-dodecane in the presence and absence of nitric acid. The distribution ratio of americium (D Am(III)) decreased with increase of absorbed dose. The presence of n-dodecane and nitric acid enhanced the radiolytic degradation of the solvent. The third phase formation behavior of Nd(III) decreased with increase of absorbed dose and the third phase was not observed at absorbed doses above 100 kGy. The recovery of Am(III) from the irradiated system was near quantitative in five contacts. The study revealed that the extraction and stripping behavior of the irradiated solvent was quite satisfactory for partitioning of minor actinides from real wastes.

The radiation stability of N,N-di-dodecyl-N′,N′-di-octyl-3-oxapentane-1,5-diamide (D3DODGA) was studied by γ-irradiation of the solvent up to a absorbed dose of 1,000 kGy. The effect of γ-irradiation on the radiolytic degradation of D3DODGA was assessed by measuring the distribution ratio of Am(III) (D Am(III)) as well as the third phase formation in the irradiated D3DODGA-n-dodecane solution. The D Am(III) in the irradiated solution decreased with increase of absorbed dose. The critical aqueous concentration of Nd(III) above which the third phase forms, increased with increase of absorbed dose. However, the limiting organic concentration of Nd(III) remained at ~25 mM irrespective of the absorbed dose. Recovery of Am(III) from the radiolytically degraded organic phase showed that back extraction of Am(III) was quantitative in a few contacts using dilute nitric acid. Our studies clearly indicated that radiolytic degradation of D3DODGA in n-dodecane is marginal even at the absorbed dose of 1,000 kGy, and therefore D3DODGA is a potential candidate for minor actinide partitioning.

The alkyl derivatives of diglycolamide (DGA) such as N,N,N´,N´-tetraoctyldiglycolamide (TODGA), N,N,N´,N´-tetraethylhexyldiglycolamide (TEHDGA) and N,N-diethylhexyl- N´,N´-dioctyldiglycolamide (DEHDODGA) are chain isomers differing only in the arrangement of carbon chain of the alkyl group. The extraction behavior of Am(III) in the solution of these diglycolamides in ionic liquid medium was studied as a function of concentration of nitric acid and diglycolamide. The results were compared with those obtained in a molecular diluent, n-dodecane. The extraction of Am(III) in ionic liquid medium increased in the order TEHDGAn-DD. The anomaly observed in ionic liquid medium was probed by IR spectroscopy and measurement of stoichiometry. The stoichiometry of Am : DGA in each case was different and that exhibited a strong influence on the observed extraction trend. The unprotonated fraction of DGA, assessed from FTIR measurements, increased in the order TEHDGA

Imidazolium nitrate functional groups (Im–NO 3 ) were anchored onto a polystyrene–divinylbenzene resin matrix, and investigated for the extraction of palladium (II) from nitric acid medium. The rate of extraction and distribution coefficient, K d , mL/g, of palladium (II) were measured as a function of extent of functionalization, and concentrations of nitric acid, sodium nitrate and palladium nitrate. K d values of palladium (II) show a maximum in 3.0 M–4.0 M nitric acid. Slope analysis of the distribution data obtained at various aqueous phase nitrate concentrations and resin phase exchanging capacity suggest the involvement of anion exchange mechanism for the extraction of palladium (II) from nitric acid medium. The ion exchange isotherm was fitted using Langmuir adsorption model and the apparent ion exchange capacity ( b = 88 mg/g) was determined. The performance of the resin under dynamic conditions was evaluated by following a breakthrough curve and the data was fitted using Thomas model.

Commercially available polystyrene-divinylbenzene (PS-DVB) resins functionalized with isothiouronium (Tulsion CH-95), phosphinic acid (Tulsion CH-96) and methylene thiol (Tulsion CH-97) moieties have been used for separating palladium from nitric acid medium. Extraction of palladium has been studied as a function of time, concentration of nitric acid and palladium. The distribution coefficients (Kd, ml/g) of palladium on sulfur based resins (Tulsion CH-95 and Tulsion CH-97) are higher (5000-104ml/g in 0.1M nitric acid) than on Tulsion CH-96 resin and decrease with increasing concentration of nitric acid. The initial rate of extraction of palladium by Tulsion CH-95 and Tulsion CH-97 resins was very rapid and the time required for the establishment of equilibrium was a function of palladium concentration in the aqueous phase. The rate data could be fitted by a second order rate equation and the magnitude of rate constant for the extraction of palladium by these resins (~102M-1. min-1) decreased in the order of: Tulsion CH-95 > Tulsion CH-97 > Tulsion CH-96. The extraction isotherms of Tulsion CH-95 were fitted by Langmuir adsorption model and the coefficients were obtained by regression. The extraction capacity of palladium on Tulsion CH-95 was found to be ~20 mg/g at 3M nitric acid. Column experiments have been conducted and the data were fitted using Thomas model. A column utilization of 75% was achieved for the extraction of palladium by Tulsion CH-95 resin.