Fixed sites plasticized cellulose triacetate membranes containing crown ethers for silver(I), copper(II) and gold(III) ions transport

Abstract

New cellulose triacetate membranes (CTA) containing the macrocyclic polyethers dibenzo-18-crown-6 (DB18C6), hexathia-18-crown-6 (HT18C6), diaza-18-crown-6 (DA18C6) and hexaaza-18-crown-6 (HA18C6) as fixed carriers were prepared, characterized and applied for facilitated transport of copper(II), silver(I) and gold(III) metal cations. FTIR, X-ray, SEM and TGA analyses showed that the polyethers crystallize inside the membrane and no new chemical bonds have been formed. A comparative study of the transport parameters across such fixed sites membranes (FSM) and supported liquid membranes (SLM) containing the same carriers has been made. The mass fluxes obtained with FSM are higher than that obtained with SLM when increasing the carrier concentration. However, beyond 1.13×10 −3 g of carrier/cm 2 of membrane, the mass flux of all three ions through the FSM reaches a value almost zero due to the formation of multilayers of carrier or aggregates onto the membrane matrix which was revealed by SEM observations of FSM-cross sections. The stability of the membrane was constant over 15 days.