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Study of competitive transport of some heavy metal cations across bulk liquid membranes containing phenylaza-15-crown-5 and cryptand 222 as carriers using flame atomic absorption spectrometry


In this study, a competitive transport procedure was used for transport process of Cr(III), Cu(II), Co(II), Cd(II), Ag(I), Pb(II), and Zn(II) metal cations across bulk liquid membrane (BLM) using phenylaza- 15-crown-5 and cryptand 222 as carriers and dichloromethane (DCM), chloroform (CHCl3), nitrobenzene (NB), 1,2-dichloroethane (1,2-DCE) and CHCl3–NB, DCM–1,2-DCE binary solvent solutions as extracting solvents. Atomic absorption spectrometry was used for determination of the concentration of the studied metal cations in source and receiving phases. The experimental results show that maximum transport rate is for silver(I) cation in the presence of the other metal cations using phenylaza-15-crown-5 as carrier and no transport was observed for the seven metal cations by cryptand 222 in all membrane systems. The effect of various parameters on the transport process was investigated. The effect of solvent on the transport efficiency of silver(I) cation was found to be in the order: NB > DCM > 1,2- DCE > CHCl3. The results also showed that the transport process of silver(I) cation through CHCl3–NB and DCM–1,2-DCE bulk liquid membranes is 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. The influence of some fatty acids as surfactant in the membrane phase on the transport of the metal cations was also investigated.