Evaluation of transition metals transport properties through a cation-exchange membrane by chronopotentiometry

In this work the transport properties of manganese, cobalt, copper, nickel and zinc through the IONICS 67-HMR-412 cation-exchange membrane were studied. The membrane conducting area, the limiting current density and the transport numbers were determined by means of chronopotentiometry. The obtained data showed that the investigated membrane is composed of approximately 93.5% of conducting area, which is a typical value for an homogeneous membrane. The transition metal ions under investigation presented high transport numbers through the 67-HMR-412 membrane, decreasing in this order: manganese > copper > zinc > cobalt > nickel. When nickel and cobalt chloride solutions were employed, a bipolar behavior was observed at over-limiting currents. The shapes of the chronopotentiometric curves also revealed a surface membrane scaling phenomenon.