Selective transport of zinc(II) from cobalt(II) sulphate solutions using a supported liquid membrane impregnated with DP-8R extractant was studied. Several variables were investigated: stirring speed of the feed phase, stirring speed and composition of the receiving phase, diluent of the organic phase. metal concentration and pH of the feed phase, extractant concentration and the lifetime of the membrane. Conditions for the separation of both metals were established: (i) aqueous feed: pH 3.0 +/- 0.02, [Co]/[Zn] molar concentration ratio near 22; (ii) receiving phase: 0.5 M sulphuric acid-, (iii) membrane phase: DP-8R 10% v/v in Exxsol D100. (C) 2004 Published by Elsevier B.V.