Electro-Osmotic Behavior of Polymeric Cation-Exchange Membranes in Ethanol-Water Solutions.

The aim of this work is to apply linear non-equilibrium thermodynamics to study the electrokinetic properties of three cation-exchange membranes of different structures in ethanol-water electrolyte solutions. To this end, liquid uptake and electro-osmotic permeability were estimated with potassium chloride ethanol-water solutions with different ethanol proportions as solvent. Current-voltage curves were also measured for each membrane system to estimate the energy dissipation due to the Joule effect.

The Correlation between the Water Content and Electrolyte Permeability of Cation-Exchange Membranes.

The salt permeability through three commercial cation-exchange membranes with different morphologies is investigated in aqueous NaCl solutions. Ion-exchange membranes (IEMs) find application in different processes such as electrodialysis, reverse osmosis, diffusion dialysis, membrane electrolysis, membrane fuel cells and ion exchange bioreactors. The aim of this paper is the experimental determination of the electrolyte permeability in the following membranes: MK-40 membrane, Nafion N324 membrane and Nafion 117 membrane.

Study of the internal morphology of cation-exchange membranes by means of electroosmotic permeability relaxations.

The effect of an ac sinusoidal perturbation of known amplitude and frequency superimposed to the usual dc applied electric voltage difference on the electroosmotic flow through three cation-exchange membranes with different morphology has been studied. A dispersion of the electroosmotic permeability on the frequency of the applied ac signal has been found for the three membranes investigated, observing that the electroosmotic permeability reaches maximum values for some characteristic values of the frequency. These characteristic frequency values, which are related to relaxation processes in heterogeneous media, depend on the membrane system and permit to obtain information about the different structures of the membrane system.

Experimental estimation of equilibrium and transport properties of sulfonated cation-exchange membranes with different morphologies.

Solvent uptake, hydraulic and electroosmotic permeabilities, true cation transport number, effective fixed charge concentration, and limiting current values have been determined in aqueous LiCl solutions for three commercial cation-exchange membranes with different morphologies and similar electric properties. The differences found in the equilibrium and transport properties of the membranes have been analyzed on the basis of their different structures. The experimental results show that the membrane morphology has an influence on the effect that the presence of an electrolyte has in the solvent uptake and in the liquid permeation.

Wetting Study of Hydrophobic Membranes via Liquid Entry Pressure Measurements with Aqueous Alcohol Solutions.

A new concept of liquid entry pressure measurements is applied to study the hydrophobicity of microporous membranes for aqueous alcohol solutions. The effects of alcohol concentration, type of alcohol, and temperature on liquid entry pressure of the membrane have been studied. Two theoretical equations for the determination of membrane pore size have been proposed.