Crown moieties as cation host units in model polyamide compounds:: Application in liquid-liquid cation extraction and in membrane cation transport

A new model polyamide compound that has a benzo-18-crown-6 moiety in the pendant structure is described. This model interacts with metal cations in the alkaline, earth alkaline, transition metal and heavy metal series. The interaction has been analyzed in terms of competitive cation extraction from aqueous solution by liquid model/dichloromethane phase. In each cation series, K(I), Ba(II), Cr(III), and Hg(II) have been selectively extracted by liquid model polyamide phases. The interaction of a dense composite model polyamide-cellu lose acetate membrane with lead(II) has been studied through its adsorption isotherm, infrared spectra and scanning electron microscopy study of the membranes before and after Pb(II) adsorption. The transport of lead nitrate through the membrane together with that of sodium chloride (for comparison), have been evaluated. (C) 2007 Elsevier Ltd. All rights reserved.