Amberlite XAD-2 impregnated organophosphinic acid extractant for separation of uranium(VI) from rare earth elements

Amberlite XAD-2 resin was impregnated with Cyanex272 {bis (2,4,4-trimethylpentyl) phosphinic acid} and Cyanex302 {bis (2,4,4-trimethylpentyl) monothiophosphinic acid}. Systematic studies of Cyanex302 impregnated XAD-2 were carried out to develop optimum conditions for uranium(VI) sorption and devise its separation from rare earth elements. Amberlite XAD-2 impregnated with Cyanex302 had poor distribution coefficients for lanthanum(III) and neodymium(III) while uranium(VI) was quantitatively sorbed from 1×10–3 M HNO3 and was recovered with 1 M HCl from the solid phase. The method proposed is simple, selective and reproducible for determination of uranium(VI) with a relative standard deviation (RSD) of 0.4 %.

The proposed method is based upon the preferential sorption of the cationic species of uranium(VI) prevailing in 1×10–3 M HNO3 media using Cyanex302 impregnated on XAD-2. The method is simple, easy to operate and selective for separation and preconcentration of uranium(VI). The preference of Cyanex302 which contains a soft donor ‘S’ for uranium(VI) was utilized for achieving high separation factors between uranium(VI) and the rare earth elements. Using the modified resin, high preconcentration factor (>500), a very high reusability for continuous usage (50 cycles) and good LOD (0.6 μg dm–3) were achieved indicating better performance over other solid phase extraction methods [7–15] for uranium(VI).