Polymer inclusion membranes (35 micrometer thick) were prepd. by mixing cellulose triacetate with di(2-ethylhexyl)phosphoric acid and a plasticizer (o-nitrophenyl-pentyl ether, o-nitrophenyl-octyl ether, bis(2-ethylhexyl)ether) in CH 2 Cl-2 soln. and evaporation of the solvent in air. The membranes effective surface 4.9 cm(2) were used for sepn. of Zn(II) and Pb(II) ions in aq. solns. at pH 2-6. The Zn ions recovery efficiency was 98.2% and that of the Pb ions recovery was 51.4%. At low pH, both ions were sepd. simultaneously (selectivity factor 8.6). The Zn recovery efficiency considerably decreased after 4 cycles of sepn. A fast increase in the ion transport rate was observed when the plasticizer content in the membrane was increased from 0.1 cm(3)/g of cellulose triacetate.