Abstract

Water and metal ion sorption of aged Nafion membrane have been studied. In order to understand water sorption,
swelling pressure and free energy of swelling have been calculated for the water sorption data on studies carried
out earlier. The larger free energy change observed on swelling of the transition metal ion form of Nafion as
compared to its original protonated form indicates that hydration is more favored for the transition metal ion
substituted membrane which supports its affinity toward these ions. Metal ion uptake data for differently treated
aged Nafion membranes were analyzed with different isotherm models, and it is confirmed that that metal ion
uptake followed chemisorption. Moreover, it was seen that pretreatment is found to affect the sorption behavior
and therefore there is a change in the model that fits best to the sorption data.