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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.

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 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.

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.

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.