Separation of zinc and bismuth by facilitated transport through activated composite membranes

This paper reports the results on the further development of activated composite membranes (ACM) containing di-2-ethyhexyl-dithiophosphoric acid (D2EHDTPA) as a carrier. The selectivity and transport properties of D2EHDTPA based ACMs towards different metal ions including bismuth and zinc appear to be interconnected with each other. It has been shown that unlike the liquid-liquid extraction of bismuth, the use of D2EHDTPA-ACM permits to recover and to concentrate bismuth from a highly saline medium without irreversible destruction of the carrier. The difference in the rates of bismuth and zinc transport through ACMs permits their separation since the former is concentrated in the stripping solution and the latter retains in the feed compartment of the membrane cell.