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

Abstract 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 UO 2 (CH 3 COO) − 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.