The competitive metal ion transport experiments of Co+2, Cd+2, Ag+, Pb+2, Ni+2 and Cu+2 were carried out by N-(2,6-dichlorobenzoyl)-N\\\\\\\',N\\\\\\\"-bis(pyrrolidinyl)-phosphoric triamide (Scheme 1) as a carrier in organic membrane phase. 2,6-Cl2-C6H3C(O)NHP(O)[NC4H8]2 has been synthesized and characterized by IR spectroscopy and single crystal X-ray diffraction. The asymmetric unit of title phosphoric triamide contains two symmetrically independent molecules. The source phase contained equimolar concentrations of metal ions at pH=5 and the receiving phase being buffered at pH=3. The following solvents were examined as membrane: chloroform (CHCl3), nitrobenzene (NB), 1,2-dichloroethane (1,2-DCE), dichloromethane (DCM), dichloromethane/1,2-dichloroethane (DCM/1,2-DCE) and dichloromethane/nitrobenzene (DCM/NB). The obtained results show that the selectivity and efficiency of transport for these heavy metal cations change with the nature of the organic solvents which were used as liquid membrane in these experiments. A good selectivity was observed for Pb+2 cation by this ligand in all membrane systems. Moreover, the selectivity of metal cations in DCM is higher than the other solvents. A non-linear relationship was found between the percent of transport of Pb+2 cation and the compositions of DCM/1,2-DCE and DCM/NB binary solutions by this ligand [1]. The effect of several factors such as the nature of carboxylic acids (stearic, fumaric and maleic acid) as surfactant in the membrane phase and the time of transport on transport efficiency of Pb+2 cation were investigated. References [1] G. Rounaghi, R.S. Khoshnood, J. Inclusion Phenom. Mol. Recognit. 55 (2006) 309.

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