Liquid membranes represent an important tool in separation science. Compared with solvent extraction, liquid membranes have shown great potential since they combine the process of extraction and stripping in a single unit operation [1–3]. Especially in case where solute concentration is relatively low and other techniques cannot be applied efficiently. In this study, competitive transport procedure is proposed for separation of Zn(II), Cd(II), Cr(III), Co(II), Ag(I), Pb(II), and Ni(II) across bulk liquid membrane (BLM) using phenylaza-15-Crown-5 and cryptand 222 as chelating agent and chloroform, dichloromethane, 1,2-dichloroethane, and nitrobenzene, as extracting solvent. Interested elements were determined by atomic absorption spectrometry. The effect of the various parameters influencing the transport process, e.g. chelating agent, type of solvent used and effect of surfactant have been established. Observations show that the phenylaza-15-Crown-5 is an efficient carrier for the Ag(I) in the presence of seven metal cation, but no transport was observed for these metal cations by cryptand 222 in all membrane systems. The effect of solvent on the transport efficiency Ag+ ion was found to be in the order of NB>DCM>CHCl3>1,2 DCE. The transport of Ag+ ion in CHCl3–NB and DCM–1,2 DCE binary mixed solvents was sensitive to the solvent composition. A non-linear relationship was observed between the transport rate of silver (I) ion and the composition of these binary mixed solvents.

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