The transport study of Co(II) ions through supported liquid membranes, based on triethanolamine (TEA), as carrier in cyclohexanone diluent, supported in polypropylene hydrophobic microporous film has been carried out. The effects of Co(II) ions, HCl (in feed) and TEA (in membrane) concentrations have been investigated. Co(II) ions concentration increase in the feed leads to an increase in flux (3.79-21.08) x 10(-7) mol/m(2) s within the concentration range, (4.21-25.31) x 10(-4) mol dm(-3) at 0.1 M HCl and 3.75 M TEA. Increase in H+ concentration by increasing HCl concentration (0.1-1 M) results into an increase in flux but a decrease in flux has been found beyond this HCl concentration in the feed providing a maximum flux, 8.19 x 10(-7) mol/m(2) s at 1 M HCl. An increase in TEA concentration in the liquid inside the membrane enhances the cobalt ions flux to 8.19 x 10(-7) mol/m(2) s at 3.75 M TEA. Further increase in its concentration leads to a decreased rate of transport of this metal ions due to an increase in viscosity of membrane liquid. The optimum flux conditions for Co(II) ions transport are 1 M HCl (feed) and 3.75 M TEA (in the membrane). TEA molecules associate with cobalt ions as (LHCoCl3)-Co-. and (LH)(2)-CoCl4, with a major contribution by the former similar to80% and similar to20% by the later depending on HCl concentration in the feed. (C) 2004 Elsevier B.V. All rights reserved.