Effect of an electric field on the transport of Th(IV) in the presence of Eu(III) and U(VI) through supported liquid membrane containing di-2-ethylhexylphosphoric acid

This paper investigates the transport of Th(IV) ions in nitric acid media through a supported liquid membrane (SLM) impregnated with di-2-ethylhexylphosphoric acid (HDEHP) in kerosene using an electric field. The transport was carried out in a three compartment cell fitted with microporous cellulose nitrate (SLM) and cation exchange membrane (Nafion). The effect of different parameters including nitric acid concentration in the feed solution, HDEHP concentration in the membrane, and HCl concentration were studied. The optimal conditions for Th(IV) transport were 0.1 mol dm−3 HDEHP, 10−3 mol dm−3 HNO3 in the feed solution, 1 mol dm−3 HCl in compartment 2 and 1 mol dm−3 HCl in compartment 3 at 25 °C. Under the optimal conditions of Th(IV) transport the recovery factor after 90 min was 0.25 without applying an electrostatic field, compared with 0.9 when the electric field was applied. The effect of electric current on the flux of Th(IV) through the membrane was also studied. The flux increased as the current density increased from 10 to 30 mA cm−2 to reach a maximum value at 30 mA cm−2 (8 × 10−9 g eq cm−2 s−1). The transport percentages of 0.3 g dm−3 Th(IV) in the presence of 0.1 g dm−3 Eu(III) and 1 g dm−3 U(VI) were 66, 84 and 15%, respectively. The determined selectivities of U(VI)–Th(IV) and Th(IV)–Eu(III) were 0.12 and 0.3, respectively, after 90 min. Therefore, the order of selectivity of this system is Eu(III) > Th(IV) > U(VI). © 2001 Society of Chemical Industry