Counter-current extraction and separation of U(VI) from a mixture of U(VI)-Th(IV)-Y(III) using tris-2-ethyl hexyl phosphate (TEHP)

Evaluation of tris-2-ethyl hexyl phosphate (TEHP) for counter-current extraction and separation of U(VI) from a mixture of U(VI)-Th(IV)-Y(III) from nitric acid medium was carried out under wide experimental conditions. Batch extraction studies were carried out to investigate the effect of nitric acid concentration in feed solution, U(VI)/Th(IV) ratio and extractant concentration and the results were compared with established solvent such as tri-n-butyl phosphate (TBP) for separation of U(VI) from nitric acid medium. McCabe-Thiele diagrams for extraction as well as stripping of U(VI) were constructed under simulated conditions. Based on batch experiments, six stage counter-current extraction studies were conducted under various TEHP concentration and it was observed that 0.1 M TEHP/n-paraffin was most suitable for selective recovery of U(VI) from a mixture of U(VI)-Th(IV). An optimized condition, 0.1 M TEHP/n-paraffin, 2 M HNO3 in feed and six number of stages was evaluated for selective extraction and stripping of U(VI) from a solution containing mixture of U(VI)-Th(IV)-Y(III) in nitric acid medium. The U(VI) in strip solution was precipitated using 30 % H2O2 at pH similar to 3. Average particle size of the final precipitate was found to be similar to 33 mu m.