Homogeneous liquid–liquid extraction of uranium(VI) from acetate aqueous solution Original Research Article

A selective and very effective concentration method for uranium(VI) was developed by the homogeneous liquid–liquid extraction method based on the ion-pair phase separation of perfluorooctanoate ion (PFOA−) with tetrabutylammonium ion (TBA+). Under the experimental conditions ([PFOA−]T=6.67×10−3 M, [TBA+]T=5.0×10−2 M, [acetate]T=0.17 M, pH 4.0), the extraction % of uranium(VI) was 96%, and the maximum concentration factor was approximately 330-fold (i.e., 90 μl of the sedimented phase was produced from 30 ml of the aqueous phase). The extracted species was estimated by the normal liquid–liquid extraction method in a water/ethyl acetate system to be UO2(CH3COO)−3·TBA+. The proposed homogeneous liquid–liquid extraction method was applied as a preconcentration method for the spectrophotometric determination of uranium(VI) with arsenazo III. The calibration graph was linear over the range 3.3×10−8–2.7×10−6 M. The relative standard deviation for the central value of the calibration graph was 1.4% (10 determinations), and the detection limit (S/N=3) was 6.0×10−10 M. When the proposed method was applied to the separation and determination of uranium(VI) added to sea water, the results were satisfactory.