Facilitated transport of Th(IV) across bulk liquid membrane by di(2-ethylhexyl)phosphoric acid

Di(2-ethylhexyl) phosphoric acid (DEHPA) has been successfully used as a ca rrier for the selective and efficient transport of Th(IV) across a bulk liq uid membrane (BLM) of chloroform. The feed comprised of a solution of pure Th(IV) or a binary mixture of Th(IV) and a cation, such as Na+, K+, Ca2+, M g2+, Cu2+, Pb2+, La3+, Fe3+, or UO22+ in water maintained at pH 2, while 0. 1 mol/L hydrochloric acid served as a stripping agent in the receiving comp artment of the permeation cell. Greater than 99% of Th4+ selectively permea ted across the membrane in less than 3 h, while the transport of other cati ons present along with thorium was less than 3% during the same time. Selec tivity of the transport of thorium was greatly affected by the presence of Fe3+ and UO22+ in the feed solution. Fe3+ could be effectively masked by th e addition of SCN- or citric acid to the feed solution but the cotransport of UO22+ could only be partially reduced by the addition of carbonate or th iocyanate to the feed solution.