Ion-pair extraction of tetravalent plutonium from hydrochloric acid medium using crown ethers

Ion-pair extraction behaviour of plutonium (IV) from varying concentrations of HCl solution was studied employing crown ethers (benzo-l5-crown-5 (B15C5), 18-crown-6, (18C6), dibenzo-18-crown-6 (DB18C6), dicyclohexano-18-crown-6, (DC18C6), dibenzo-24-crown-8 (DB24C8) and dicyclohexano-24-crown-8 (DCH24C8)) in nitrobenzene as the extractant. Ammonium metavanidate was used as the holding oxidant in the aqueous phase and the conditions necessary for the quantitative extraction of the tetravalent ion were found. The co-extraction of species of the type [HL⁺].[HPu(Cl) ₆ ^– ] and [HL⁺]2·[Pu(Cl) ₆ ^2– ] as ion-pairs (where L represents the crown ether) is suggested.     

Laboratory studies on the adsorption behavior of americium

With increasing global nuclear activities, there is a growing interest in understanding the migration behavior of transuranic elements in the terrestrial environment. The laboratory investigations on the adsorption behavior of AM(III) (10^–7M) in aqueous solutions showed that there was not adsorption of Am(III) on glass or polyethylene vials from aqueous solutions at pH<3. The rate of adsorption was found to be inversely related to the (H⁺) in the pH range 4–7. It was also found to be strongly influenced by stirring/shaking as well as by the presence of particulate matter in the aqueous phase. The presence of particulate matter (>0.6 m) in the aqueous solutions significantly inhibits the adsorption rate. Attempts to fit the kinetic data (collected on filtered [particle size >0.6 m] or unfiltered distilled water at pH 6) to the reversible or irreversible first order rate equation did not successfully indicate the complexity of the adsorption process. The presence of 20mg/liter of humic acid at pH 6.3 completely inhibits the adsorption of Am on glass surfaces.     

Ion-pair extraction of uranyl ion from aqueous medium using crown ethers

Ion-pair extraction behaviour of uranyl ion from aqueous solutions was studied at pH 3.0 employing crown ethers viz. benzo 15 crown 5 (B15C5), 18 crown 6 (18C6), dibenzo 18 crown 6 (DB18C6), and dibenzo 24 crown 8 (DB24C8) in chloroform as the organic phase and picric acid as the organophilic counter anion. The stoichiometry of the extracted species corresponded to [UO₂(crown ether)_n]²⁺·[pic⁻]₂ where n=1.5 for benzo 15 crown 5 and 1 for 18 crown 6 as well as dibenzo 18 crown 6. Adducts of DB24C8 could not be observed as practically no extraction was possible using this reagent. The separation behaviour of fission products from an irradiated uranium target was also studied. An interesting observation on the separation of trivalent lanthanides from uranyl ion is reported.     

3-Phenyl-4-benzoyl-5-isoxazolone: A promising chelate extractant for actinide separation from acidic nuclear waste solutions

In the presence of tri-n-octyl-phosphine (TOPO) oxide, 3-phenyl-4-benzoyl-5-isoxazolone (PBI) has been found to be a promising chelate extractant for the partitioning of actinides from acidic nuclear waste solutions. Quantitative extraction of Pu and U is possible in the nitric acid concentration range 1–6 M, whereas Am can be extracted only from solutions with an acidity . Extraction studies of Am and U under varying loading conditions are also carried out and conditions for quantitative stripping are arrived at.     

Use of oxide minerals to abate fluoride from water

The removal of fluoride from aqueous solutions has been investigated using various oxide ores such as refractory grade bauxite, feed bauxite, manganese ore, and hydrated oxides of manganese ores (WAD). The refractory grade bauxite showed promising results. The studies were carried out as functions of contact time, pH, concentration of adsorbents, concentration of adsorbate, and temperature. The adsorption was rapid during the initial 5 min but equilibrium was attained within 120 min. The adsorption followed first-order kinetics. The present system followed the Langmuir adsorption isotherm model. Various thermodynamic parameters such as free energy, enthalpy, entropy, and equilibrium constants were calculated. The isosteric heat calculations showed that the adsorption process followed a heterogeneous model.