Malpan Pailo Antony

The aggregation behaviour of reverse micelles, formed during the extraction of neodymium nitrate and nitric acid, in an organic phase composed of tetra‐bis(2‐ethylhexyl) diglycolamide (TEHDGA) in n ‐dodecane ( n ‐DD) was studied, at various temperatures. The organic phase, 0.2 M TEHDGA/ n ‐DD was equilibrated with aqueous solutions of nitric acid in the presence and absence of neodymium nitrate. At certain nitric acid and Nd(III) concentration in aqueous phase, the organic phase underwent splitting into two phases, with top phase known as “diluent rich phase”, the other one known as “third phase” or “metal ion rich phase”. Dynamic light scattering, attenuated total reflectance (ATR) ‐Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopic methods were employed for probing the size and distribution of aggregates present in the organic phase before and after splitting. The investigations revealed that the aggregates, formed in organic phase, interact efficiently with the extracted metal ions and these interactions increased with increase in the concentration of nitric acid and neodymium nitrate in organic phase. In addition, the interaction among the reverse micelles in third phase appear to be very strong as compared to that observed in the organic phase before third phase formation, and such strong interactions resulted in a merger and narrow distribution of reverse micelles in third phase.

The rate of ion exchange of Eu(III) from semi-infinite bath containing dilute nitric acid solution was studied on a macroporous bifunctional phosphinic acid resin. The influence of particle size, concentration of nitric acid and temperature on the uptake of Eu(III) was examined. The kinetic data were fitted into the Reichenberg approximate solution, based on the Nernst–Planck resin diffusion model, that relates the fractional attainment of equilibrium (U_t) and internal diffusion coefficient (D_A). The measured D_A was of the order of 10⁻¹³ m²/s, and it was found to increase with the increase of temperature, and decrease with the increase of particle size of the resin and concentration of nitric acid.

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.

Chromatographic resin containing extractants such as octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) or bis-(2-ethylhexyl)phosphoric acid (HDEHP) or mixture of extractants (CMPO + HDEHP) in an acrylic polymer matrix was prepared and studied for the extraction of Am(III) and Eu(III) over a range of nitric acid concentration. The effect of various parameters such as concentration of nitric acid in aqueous phase and the concentration of CMPO and HDEHP in the resin phase was studied. The distribution coefficient of Am(III) and Eu(III) in the impregnated resin increased with increased in the concentration of nitric acid for CMPO-impregnated resin, whereas a reverse trend was observed in HDEHP impregnated resin. In case of resin containing both the extractants, synergism was observed at low nitric acid concentration and antagonism at high nitric acid concentration. The mechanism of extraction was probed by slope analysis method at 0.01 and 2 M nitric acid concentrations. Citrate-buffered DTPA was used for the selective separation of Am(III), and a separation factor of 3–4 was obtained at pH 3.

Extraction of Am(III) from nitric acid medium was carried out in a solution of benzoylpyrazolone (HPMBP) dissolved in 1-butyl-1-methylpyrrolidinium bis(trifluoro-methanesulfonyl)imide ([C₄mpyr][NTf₂]) ionic liquid. The extraction behavior of Am(III) in ionic liquid phase was investigated as a function of various parameters, such as pH of aqueous phase, duration of equilibration, and concentration of ionic liquid and nitrate in aqueous phase. Appreciable extraction was obtained at low pH medium (< pH 2) unlike other diketone based extractant. Extraction of Am(III) in ionic liquid was compared with that observed in a molecular diluent, n-dodecane (n-DD) under similar experimental condition. Remarkably high distribution ratio was observed in IL medium as compared to n-DD medium. The slope analysis of the extraction data was carried out to evaluate the mechanistic aspects of extraction. Extraction mechanism was different from conventional molecular diluent. Recovery of americium from the loaded ionic liquid phase was also studied using nitric acid.

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.