Correlations between water uptake and effective fixed charge concentration at high univalent electrolyte concentrations in sulfonated polymer cation-exchange membranes with different morphology

► Water uptake of different sulfonated polymer exchange-membranes was investigated in different aqueous electrolyte solutions. ► Effective charge concentration of different sulfonated polymer exchange-membranes was investigated in different aqueous electrolyte solutions. ► Relationships were found between charge effectiveness and water uptake for membranes with different structures. Water uptakes properties and effective fixed charge concentration have been determined in aqueous electrolyte solutions (LiCl, NaCl and KCl) for different commercial sulfonated polymer cation-exchange membranes with different morphology. Differences in the water uptake properties and in the membrane effective fixed charge concentration has been found, which have been analyzed on the basis of the different membrane structures. The experimental results show correlations between the water uptake and the loss of the membrane selectivity at high electrolyte concentrations which are dependent on the membrane morphology. Relationships are found which permit to estimate the membrane effective fixed charge concentration from equilibrium and morphological properties with the advantage of avoiding the need for membrane potential measurements.