Insight of solvent extraction process: Reassessment of trace level determinations.

Solvent extraction is hoary yet modern technique with great scope of research due to the various intriguing phenomena in the system. Tri-n-butyl phosphate (TBP) is a well known extractant which has been extensively used for separation of uranium matrix prior to elemental profiling. In this paper, one of the impurities namely Fe is being considered as it posed a challenge to the separation due to its co-extraction with TBP along with uranium. In these studies, for the first time, the existence of cation-cation inner sphere complexes between the UO2(2+)and Fe(3+) ions in both aqueous and organic phases have been establisted in addition to the selective separation of iron from uranium sample matrix using only TBP. The data from both spectrophotometric and thermophysical studies corroborated one another confirming the presence of cation-cation interactions (CCIs). The developed solvent extraction with only TBP showed almost no interferences on the iron extraction from matrix uranium and other co-ions like aluminum and copper. This has been the first time application of pure TBP for selective removal of iron from uranium samples. The procedure possessed excellent reproducibility and robustness.

N-benzoyl-n-phenylhydroxylamine impregnated Amberlite XAD-4 beads for selective removal of thorium.

n-Benzoyl-n-phenylhydroxylamine impregnated Amberlite XAD-4 beads were used for the removal of Th(IV) from a mixture of ions. The impregnated XAD was characterized using different techniques like weight and colour change, IR spectra, surface area and pore size measurements to confirm the presence of n-BPHA within the macroreticular resin structure. The experimental conditions were optimized to make the separation fast and selective. It was seen that the maximum sorption was achieved in the pH range of 3-7.5 and uptake was nearly complete within half an hour. The results obtained in the present study were subjected to extensive modelling in order to get a complete understanding of the sorption process. It is seen that the maximum uptake was calculated to be 500 mg/g and has very fast kinetics it was seen that the process is chemisorption. It was further deduced from the modelling that the overall sorption process was controlled dominantly by external mass transfer. Considering the simplicity this procedure, the present study has a possible application for the removal of thorium from different mixtures.

Boroaluminosilicate glasses: novel sorbents for separation of Th and U.

Boroaluminosilicate glass having a specific composition could be successfully used for the selective uptake of thorium from a mixture containing uranium by controlling the solution pH only. Single ion uptake studies showed that the uptake of uranium and thorium was maximum at pH of 4.5 and 7.5, respectively. But uptake studies using mixtures with uranium and thorium showed that irrespective of the pH, the uptake of thorium was higher than that of uranium.

Barium borosilicate glass as a matrix for the uptake of dyes.

Barium borosilicate (BBS) and sodium borosilicate (SBS) glass samples, prepared by the conventional melt-quench method, were used for the uptake of Rhodamine 6G dye from aqueous solution. The experimental conditions were optimized to get maximum uptake and was found to be 0.4 mg of dye per gram of BBS glass sample. For the same network former to modifier ratio, barium borosilicate glasses are found to have improved extent of uptake for the dye molecules from aqueous solutions compared to sodium borosilicate glasses. Based on 29Si MAS NMR studies on these glasses, it is inferred that significantly higher number of non-bridging oxygen atoms present in barium borosilicate glasses compared to sodium borosilicate glasses is responsible for its improved uptake of Rhodamine 6G dye. 11B MAS NMR studies have confirmed the simultaneous existence of boron in BO3 and BO4 configurations in both barium borosilicate and sodium borosilicate glasses. The luminescence studies have established that the dye molecule is incorporated into the glass matrix through ion exchange mechanism by replacing the exchangeable ions like Na+/Ba2+ attached with the non-bridging oxygen atoms present in the glass.

Borosilicate glasses modified with organic ligands: a new selective approach for the removal of uranyl ion.

Barium borosilicate glass was found to have high uptake capacity for many cations. To improve its selectivity, surface modification was carried out. In order to make the glass selective towards uranyl ion, organic ligands like tri-n-octylphosphine oxide (TOPO) and 8-hydroxy quinoline (Oxine) were used. It was observed that the surface modification resulted in the change in uptake property of the glass. The uptake process was faster and within 5 h, 90% of the uranyl ion could be taken up from a 0.01 mM solution. With use of the modified barium borosilicate glass and EDTA as masking agent, uranyl ion could be selectively removed from mixtures of cations.