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

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)=6.67x10(-3) M, [TBA(+)](T)=5.0x10(-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 mu l 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 arsenate III. The calibration graph was linear over the range 3.3x10(-8)-2.7x10(-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 6.0x10(-10) M. When the proposed method was applied to the separation and determination of uranium(VI) added to sea water, the results were satisfactory. (C) 1999 Elsevier Science B.V. All rights reserved.