Affinity membranes for the extraction of Cd metal ions by facilitated transport ensured by a new thiacalix[4]arene complexing agent incorporated in supported liquid membranes (SLM)

A thiacalix[4]arene dissolved in NPOE for incorporation in a supported liquid membrane, is shown to ensure a transmembrane transport flux of Cd2+ ions with an order of magnitude higher than that obtained with a very lipophilic carrier such as Lasalocide A, according to a mechanism of active facilitated transport (coupled to a pH gradient). Liquid–liquid (water-NPOE) extraction experiments confirmed the good affinity of the thiacalix[4]arene for the Cd2+ ions at the interface between an aqueous medium of pH=8 and NPOE organic phase, as well as its almost complete release in water when the pH of the aqueous phase is changed to acid.