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 carrier for the selective and efficient transport of Th(IV) across a bulk liquid 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+, Mg2+, 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 compartment of the permeation cell. Greater than 99% of Th4+ selectively permeated across the membrane in less than 3 h, while the transport of other cations present along with thorium was less than 3% during the same time. Selectivity 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 the 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 thiocyanate to the feed solution.