Comparative study of liquid uptake and permeation characteristics of sulfonated cation-exchange membranes in water and methanol

Liquid permeation and uptake measurements of pure water and methanol were carried out using three commercial cation-exchange membranes: Nafion-117 (perfluorinated polyethylene with pendant ether-linked side chains terminated with sulfonated groups), MK-40 (microparticles of polystyrene–divinylbenzene with sulfonic groups randomly dispersed in a polyethylene matrix) and CR61-CZL-412 (crosslinked sulfonated copolymer of styrene–divinylbenzene). Methanol uptake by the Nafion-117 membrane was higher than that of water, in contrast, for MK-40 and CR61-CZL-412 membranes the opposite behavior is observed. Differences in the water and methanol liquid uptakes by the membranes were discussed in terms of the chemical interaction between the liquids and the polymers, and also on the size of the liquid molecules. On the other hand, the methanol permeation flow values through the membranes were higher than those of water for all the studied membranes.