Selective and uphill transport of uranyl ion in the presence of some base metals and thorium across bulk liquid membrane by di(2-ethylhexyl) phosphoric acid

Di (2-ethylhexyl) phosphoric acid has been successfully used as a selective carrier for the transport of uranyl ion across a bulk liquid membrane of chloroform. More than 98% uranium is selectively transported from a binary or a multi component mixture of cations in less than 3 hr. The pH of the feed solution was kept between 4.0 and 5.0 while 0.1 M hydrochloric acid served as a stripping agent in the receiving compartment. The co-transport of Zn2+ and Fe3+ was significantly small (< 4%) but that of thorium was very high. However, the interference from Th(IV) and transition metal ions could be eliminated by the addition of EDTA (E. Merck (India) Ltd., Mumbai) to the feed solution. Different experimental parameters affecting the transport process were optimized and the membrane separation method was applied to the recovery and pre-concentration of uranium from synthetic seawater sample. It was concluded that approximately 98% of uranium could be recovered and a hundred fold pre-concentration of the metal could be accomplished in less than 3 hr.