Experimental determination of the streaming potential across cation-exchange membranes with different morphologies

• Application of non-equilibrium thermodynamics theory to the study of the transport processes in charged membranes.
• Heterogeneous membranes exhibit higher liquid content than homogeneous membranes.
• The higher the membrane liquid content, the higher the streaming potential across the membranes is.
• The streaming potential across the membranes increases linearly with the established pressure difference.

Liquid uptake and streaming potential have been determined in aqueous sodium chloride solutions for five different commercial sulfonated polymer cation-exchange membranes. The selected membranes have distinct morphologies and electrochemical properties. Differences in the liquid uptake properties of the membranes have been found, which have been analysed on the basis of the structure and the chemical properties of the membranes. In most of the membranes analyzed, the higher the liquid content of the membranes, the lower the effective concentration of fixed charges in the membranes. The streaming potential across the membranes increases linearly with the established pressure difference, and it is larger in heterogeneous membranes than in homogeneous ones. In general, the higher the membrane liquid content, the higher the streaming potential across the membranes.