Characterisation of Nafion®117 membrane modified chemically with a conducting polymer: An application to the demineralisation of sodium iodide organic solutions

The commercial Nafion®117 cation exchange membrane is a good material for high proton conduction. In the present work, we studied transport numbers of monovalent and divalent metal cations (Na+, Zn2+) in competition with the proton through this membrane as well as membrane chemically modified with a conducting polymer by using the electrochemical Hittorf method. The oxidant concentration (FeCl3) used to polymerise the pyrrol inside the membrane matrix influences greatly the modification. The modified membrane has been used in an electrodialysis pilot having three compartments. The electrode compartments contain aqueous sulphuric acid solutions, whereas the central one contains an organic electrolytic solution (sodium iodide + organic solvent). The solvents used are methanol, dioxan, N-methylformamide and acetonitril. Characterisation of ionic transport and permeability of solvent have been investigated. The results obtained are compared to those measured using unmodified membranes. The application of this work could also concern pollutants removal (metal cations) from industrial effluents using electromembrane techniques. Addition of solvent in electrolyte solution could modify the properties of transport and in certain case improve the extraction. The process could be achieved in two stages: firstly, the salt is separated from the organic effluent and secondly, the impurities are removed to obtain the purified solvent. Thus, this research work opens perspectives towards the separation between different constituent solvents.