Abstract
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. Considering the Onsager reciprocity relations, the streaming potential coefficient was discussed in terms of ethanol content of the solutions and the membrane structure. The results showed that more porous heterogeneous membrane presented lower values of liquid uptake and streaming potential coefficient with increasing ethanol content. Denser homogeneous membrane showed higher values for both, solvent uptake and streaming coefficient for intermediate content of ethanol.
Highlights
Membrane processes are widely studied for numerous applications of practical interest.Linear non-equilibrium thermodynamics is one of the theoretical approaches used to describe transport phenomena in membrane systems [1]
Only one thermodynamic force acts usually over it, or one of the thermodynamic flows becomes null in order to determine the different phenomenological coefficients
Three commercial ion exchange membranes with different structures were compared in terms of liquid uptake and electrokinetic properties on ethanol-water media
Summary
Linear non-equilibrium thermodynamics is one of the theoretical approaches used to describe transport phenomena in membrane systems [1]. Within this approach, each thermodynamic flow, Ji , depends on every thermodynamic force, Xk , acting in the system, Ji = X Lik Xk (1). The Onsager relation holds Lik = Lki. In studying a system, only one thermodynamic force acts usually over it, or one of the thermodynamic flows becomes null in order to determine the different phenomenological coefficients. Only one thermodynamic force acts usually over it, or one of the thermodynamic flows becomes null in order to determine the different phenomenological coefficients From these known coefficients and the linear phenomenological Equation (1), it is possible to determine the total flow through the system when various forces act over it
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