Potentiometric selectivity of ion-exchange Nafion membranes

The potentiometric selectivity coefficients (PSC) of membranes based on the Nafion-117 and Nafion-417 films are determined at 25 degrees C by the method of mixed solutions at a constant ionic strength (which is defined by the main ion) in the series of cations Na+ and R4N+ with changing radii, where R = H, Me,..., Pent. The PSC data are compared with those for membranes based on polyvinyl chloride plasticized by dibutylphthalate and with the calculated distribution coefficients and relative mobilities of the ions. The comparison is used to show that PSC of the Nafion membranes can be determined by diffusional or ion-exchange characteristics of the potential-determining ions, depending on their position in the series studied.