Facilitated transport of metal ions through composite and polymer inclusion membranes

The application of activated composite membranes (ACMs) and polymer inclusion membranes (PIMs) for the transport of Pb(II), Cd(II), and Zn(II) in a continuous extraction-reextraction system using organophosphorous acids as carriers was examined. The ion carriers, DEHPA, Cyanex 301, and Cyanex 302, were incorporated into PIMs composed of cellulose triacetate as a support and o-nitrophenyl pentyl ether as a plasticizer. ACMs were pepared by interfacial polymerization and PIMs by physical immobilization of carrier into plasticized cellulose triacetate. The polyamide top layer of the ACM immobilizes organophosphorous acids by trapping them in the polymer net during the interfacial polymerization process. Transport of Pb(II), Cd(II), and Zn(II) ions through ACM and PIM membranes was determined. Highly selective Pb(II) separation was achieved in the ACM system with Cyanex 301; the transport rate of process, however, was higher for the PIM system. It was found that ACM has much higher stability than PIM. A membrane-based process for Zn(II) or Pb(II) recovery from hydrometallurgical aqueous effluents has been proposed.