Separation and recovery of metal ions using conducting polymers

Two different approaches for achieving separation and recovery of metal ions from aqueous solutions using conducting polymers have been demonstrated. The first approach is the electroless recovery of metal ions using conducting polymer modified RVC (Reticulated Vitreous Carbon) composite materials, while the second is the electrochemically controlled transport of metal ions across conducting polymer membranes. For the electroless recovery of gold from aqueous solutions, a range of conducting polymers including polypyrroles, polyanilines and polythiophenes with different reduction potentials were synthesized and characterized. Both conducting polymer modified RVC composite materials and conducting polymer membranes were used. Recovery of gold from acidic, chloride containing solutions and basic, cyanide containing solutions was demonstrated. The capacity of different conducting polymer materials to take up gold complexes from solution, and the rate of gold uptake, were both examined. In addition, the effects of varying the polymer, polymer dopant, polymer redox state, polymer surface area and polymer thickness have also been examined. The results were compared to those obtained using the activated carbon adsorption method. The synthesis and characterization of new polypyrrole and polythiophene membranes, and their use for electrochemically controlled transport of metal ions is described. The properties of membranes were characterised using numerous techniques. The data indicated that all membranes investigated are adequate for use in studies of electrochemical control of transport. Polypyrrole membranes doped with the metal ion chelating agent bathocuproinedisulfonic acid were prepared and used to transport alkali metals, alkaline earth metals and transition metals. Transport of nickel, and cobalt was demonstrated for the first time. In many instances the flux of metal ion across the membrane was greater than previously observed. Membranes composed of poly(bithiophene) doped with a sulfated poly(β- hydroxyether) (PBT/S-PHE) were synthesized and characterized, and shown to have excellent mechanical properties. PBT/S-PHE membranes were shown to be stable in solutions containing either gold chloride or cyanide complexes, and were used to effect the electrochemically controlled transport of [AuCI4]- for the first time.