Permselectivity and temperature-dependent permeability of polyaniline membranes

An understanding of the mechanism of permeability in both doped and undoped polyaniline is obtained through permselectivity studies. Pervaporation experiments are used to determine the permeability of carboxylic acid/water mixtures through both doped and undoped polyaniline membranes. Swellability experiments are used to determine solubilities, enabling diffusivity values to be calculated. Doped polyaniline membranes show a marked improvement in separating water from carboxylic acid/water mixtures as compared to undoped membranes, particularly in the cases of acetic acid and propionic acid. However, the permeant fluxes of acetic acid/water mixtures through doped polyaniline membranes are lower than the fluxes through undoped polyaniline. The permeability behavior of acetic acid, water and acetic acid/water mixtures are investigated between 20 °C and 100 °C. The flux of 50% acetic acid/50% water mixtures through doped polyaniline doubles between 20 °C and 85 °C, while the flux through undoped polyaniline over the same temperature range shows a 10-fold increase. From this data, the activation energies of permeation for 50% acetic acid/50% water are calculated to be 2.5 kcal/mol through doped polyaniline membranes and 8.1 kcal/mol through undoped polyaniline.