Observable Streaming Potential in Membranes

Abstract

Theories describing the electrokinetic processes in membranes usually involve nonobservable variables. One of these phenomena is the streaming potential, i.e., the electric potential generated by a pressure difference imposed across the membrane system. In this work the streaming potential is successfully described by using observable variables in the framework of thermodynamics of irreversible processes. The observable electric potential is the central quantity of the transport equations. The relaxation with time of this electric potential difference is well explained by the solute flux in these transport equations. The fluxes and forces defined in the formulation permit one to analyze the transport of the constituents through the membrane pores.

Bulk Streaming Potential in Poly(acrylic acid)/Poly(acrylamide) Hydrogels

“…The response of polyelectrolyte hydrogels to environmental influences, such as changes in pH and temperature, has received sustained scientific interest. Deformation of a polyelectrolyte gel subjected to an electric field was first reported by Tanaka et al The electromechanical properties of such gels have since been explored in view of a wide range of applications, − including fuel cells, environmental filtration, and artificial muscles. − Most work has been devoted to actuators, which convert electrical signals into a mechanical response. By contrast, the reverse effect, where the gel is exposed to a mechanical stress which then results in a measurable electrical field, has not been studied as thoroughly.…”

Thermodynamics of Electrochemical Systems

“…Finally, the thermodynamic theory of electrochemical systems with pressure gradients have been studied in ref ; a Nafion-120 membrane with a 0.010 mol dm -3 NaCl solution is considered. Ag|AgCl electrodes are used.…”

“…During the last years several, nonequilibrium electrochemical systems have been studied using the electric potential measured at the electrode terminals. − These studies have been developed within the theoretical framework of the thermodynamics of irreversible processes . The new transport equations have the generality of thermodynamic theory and do not require that the system be modeled.…”

Transport Equations of Electrodiffusion Processes in the Laboratory Reference Frame

“…In our case, we choose a set formed by independent and observable forces, which the experimental arrangements provided straightforwardly. [6][7][8][9] We consider the simple case of a solution with a neutral solvent and an electrolyte A ν+ B ν-with two ionic constituents A z+ and B z-; temperature and pressure are constant. We assume that the solution is locally well defined by the solute concentration, c 2 ; the eventual deviation with respect to the electroneutrality condition is unnecessary and strictly not evaluable.…”

“…There are different ways of expressing the dissipation function of a phenomenon according to the thermodynamic forces selected for describing the local irreversibility; each one of these sets of thermodynamic forces emphasizes different coupled phemomena. In our case, we choose a set formed by independent and observable forces, which the experimental arrangements provided straightforwardly. − …”