Transport Study of Metal Cations Through a Bulk Liquid Membrane Using Benzo-18-crown-6 as an Ionophore

The transport experiments of Cr(3+), Co(2+), Cu(2+), Zn(2+), Cd(2+), Ag(+), Pb(2+) metal cations were carried out by benzo-18-crown-6 (B18C6) using chloroform (CHCl(3)), 1,2-dichloroethane (1,2-DCE), dichlorometh-ane (DCM), nitrobenzene (NB), chloroform-nitrobenzene (CHCl(3)-NB) and chloroform-dichloromethane (CHCl(3)-DCM) binary mixed solvents as liquid membranes. The aqueous Source phase consisted of a buffer solution (CH(3)COOH/CH(3)COONa) at pH = 5 and containing an equimolar mixture of these 7 metal cations. The organic phase contained the macrocycle ligand, benzo-18-crown-6 (B18C6) as an ionophore and the receiving phase consisted of a buffer solution (HCOOH/HCOONa) at pH = 3. The obtained results show that benzo-18-crown-6 is a highly selective ionophore for Pb(2+) cation. The sequence of transport efficiency for Pb(2+) cation in organic solvents was found to be : DCM > NB > 1,2-DCE > CHCl(3). The influence of the stearic acid, palmitic acid and oleic acid in the membrane phase on the ion transport was investigated. A non-linear behaviour was observed for variation of the transport rate of Pb(2+) cation vs. the composition of CHCl(3)-NB and CHCl(3)-DCM binary mixtures.