EQUILIBRIUM AND KINETIC-STUDIES ON THE SEPARATION OF URANIUM AND THORIUM FROM NITRIC-ACID MEDIUM BY LIQUID EMULSION MEMBRANE-BASED ON TRIOCTYLPHOSPHINE OXIDE EXTRACTANT

It was found that the extraction percent (E%) values of U(VI), Th, Zr and Fe(III) from 0.1 mol dm(-3) (M) HNO3 solution by 0.1 M TOPO in cyc lohexane solution are 98, 78, 85 and 85%, respectively. Among these el ements, only U(VI) and Th were found to be stripped from their organic phase by 0.1 M sodium citrate solution. Cerium, copper and cadmium we re not extracted by trioctylphosphine oxide (TOPO) under similar condi tions. Based on these equilibrium results, a liquid emulsion membrane (LEM) was prepared from TOPO/Span 80/sodium citrate and the factors af fecting its stability were studied. Permeation of U(VI) into this memb rane was kinetically studied in detail. Its forward permeation rate wa s found to be mainly dependent on TOPO concentration and slightly depe ndent on U(VI) and HNO3 concentration of the external phase. Permeatio n results showed that it is possible to recover 98% of U(VI) and 82% o f Th from 0.1 M HNO3 solution containing Ce, Zr, Fe(III), Cd, and Cu b y the membrane. The recovered U(VI) and Th were contaminated with less than 2% of Fe(III).