Electrochemically controlled transport of metal ions across polypyrrole membranes using a flow-through cell

Electrochemically facilitated transport of an aqueous mixture containing Na+. K+, Ca2+ and Mg2+ across two different conducting polymer composite membranes has been examined. The two membranes consisted of polypyrrole (PPy) doped with either polystyrenesulfonate/dodecylbenzenesulfonate (1%) (PPy/PSS/DBS) or polyvinylphosphate/dodecylbenzenesulfonate (1%) (PPy/PVP/DBS). In both cases the conducting polymer was deposited onto a platinum sputter-coated polyvinylidene fluoride filter. For both membranes, transport experiments were conducted using a flow-through cell with both pulsed potential and constant potential techniques. In addition, facilitated transport in a stirred solution cell with pulsed potential method was also investigated. The flux of Na+, K+ and Ca2+ ions was significantly higher when transport was examined using the flow-through cell and driven by application of a constant potential. In all the systems examined, the flux of metal ions followed the sequence Na+ > K+ > Ca2+ > Mg2+. Transport of each metal ion was more facile under all conditions examined across composite membranes containing PPy/PSS/DBS. Atomic force microscopic examination of the surface of this membrane showed it to have a significantly smoother surface morphology compared to PPy/PVP/DBS. (C) 2001 Elsevier Science BY. All rights reserved.