There has been a growing interest in the transport of metal cations across artificial membranes. Transport of cations across an organic liquid membrane which separates two water phases, has been extensively investigated [1]. Among the separation techniques, ion transport is a selective, efficient and simple method. In the recent years, the liquid membrane has widely been used to study ion transport under a concentration gradient [2-5]. The aim of the present study is to investigate the selectivity of 5,12- di(phenoxymethyl)-1,4-dioxa-7,10-dithiacyclododecane-2,3-dione as an ion carrier towards seven metal cations involving Cr3+,Co2+, Cu2+, Ag+, Cd2+, Zn2+ and Pb2+ that are present together in solution at equimolar concentrations across bulk liquid membrane.In this paper, we report the results of competitive of seven-metal membrane transport from an aqueous source phase through an organic membrane into an aqueous receiving phase have been carried outusing the ionophore present in the organic phase. Fluxes and selectivities for competitive metal cation stransport across bulk liquid membranes have been determined in a variety of chlorinated hydrocarbon and aromatic hydrocarbon solvents. The membrane solvents include: dichloromethane(DCM), chloroform(CHCl3), 1,2-dichloroethane(1,2-DCE), andnitrobenzene(NB) and also in chloroform-dichloromethane(CHCl3-DCM) and chloroform-nitrobenzene(CHCl3-NB) binary mixtures. Although the selectivity for silver(I) cation in all of these organic solvents is fundamentally similar, but the most transport rate for Ag(I) was obtained in dichloromethane. The sequence of transport rate for silver ion in organic solvents was: DCM > CHCl3 >1,2-DCE > NB. A linear relationship was observed between the transport rate of silver ion and the composition of CHCl3-DCM, but a non-linear behavior was observed in the case of CHCl3-NB binary solution.The influence of the stearic, palmetic and oleic acids as surfactant in the membrane phase on the transport of the metal cations was also investigated.

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