Selective Liquid Membrane Transport of Lead(II) by an Acyclic Polyether Dicarboxylic Acid Ionophore.

The effects of the chain structure and substitutents in six acyclic polyether dicarboxylic acids and one acyclic polyether carboxylic acid upon the efficiency and selectivity of pH-driven Pb(2+) transport in a bulk chloroform membrane system have been assessed. Among the carriers, 1,2-bis[2-(o-carboxyphenoxy)ethoxy]-4-tert-butylbenzene (1) is found to exhibit high selectivity for transport of Pb(2+) compared with alkali metal cations and a variety of other divalent metal ion species. Ionophore 1 also extracts Pb(2+) from aqueous solution into chloroform with the loss of two protons. A 1:1 complex of Pb(2+) with di-ionized 1 was isolated.