COPPER(II) COMPLEXATION BY HYDROPHOBIC SINGLE-ALKYL AND DOUBLE-ALKYL CHAIN LIGANDS SOLUBILIZED IN AMMONIUM SURFACTANT VESICLES

Copper complexation by hydrophobic ligands solubilized in vesicular sy stems has been studied as a means to carry out selective metal extract ion and decontamination of aqueous effluents. The vesicular systems we re constituted of dimethyldi-n-alkylammonium bromides with the alkyl c hains being octadecyl (DODAB), hexadecyl (DHAB), or dodecyl (DDAB). Th e rate of complexation with a single-chain ligand, [(hexadecylamino)me thyl]-2-(hydroxymethyl)pyridine (C(16)NHMePyr), and a double-chain one , i-n-dodecylamino)methyl]-2-(hydroxymethyl)pyridine (diC(12)NMePyr), was investigated by the stopped-flow technique. The results have shown that rigidifying the amphiphilic layer, compared to those of classica l micelles, does not reduce the rate of complexation and that the melt ing of the alkyl chains (gel to fluid transition) has the result of de creasing the rate, but only as far as double-chain ligands are concern ed. The observation of two kinetic processes in some cases is discusse d in relation with the problems of lateral diffusion and flip-flop kin etics. The effective removal of copper ions was controlled by ultrafil tration of the vesicles containing the metal/ligand complexes. The yie ld of copper extracted was found to be lower than that with classical micelles under similar conditions, and only low metal content could be used due to stability problems (osmotic stress).