Onsager’s reciprocal relations in electrolyte solutions: I. Sedimentation and electroacoustics

Onsager’s reciprocal relations in electrolyte solutions: I. Sedimentation and electroacoustics

Gourdin-Bertin, S.
Chassagne, C.
Bernard, O.
Jardat, M.

Civil Engineering and Geosciences

Hydraulic Engineering

2015-08-14

In the framework of irreversible thermodynamics, we show that the sedimentation current in electrolyte solutions is mathematically equivalent to the low frequency limit of the ionic vibration current, appearing in the presence of an acoustic wave. This non-trivial result is obtained thanks to a careful choice of the reference frame used to express the mass fluxes in the context of electroacoustics. Coupled transport phenomena in electrolyte solutions can also be investigated in a mechanical framework, with a set of Newtonian equations for the dynamics of charged solutes. Both in the context of sedimentation and of electroacoustics, we show that the results obtained in the mechanical framework, in the ideal case (i.e., without interactions between ions), do satisfy the Onsager’s reciprocal relations. We also derive the general relation between corrective forces accounting for ionic interactions which must be fulfilled so that the Onsager’s reciprocal relations are verified. Finally, we show that no additional diffusion term needs to be taken into account in the flux of solutes (far from the walls), even if local concentration gradients exist, contrarily to what was done previously in the literature.

acoustic waves
entropy
sedimentation
electric currents
diffusion

http://resolver.tudelft.nl/uuid:261e8bd9-e892-4375-8748-1b339395be60

American Institute of Physics

0021-9606

https://doi.org/10.1063/1.4927467

Journal of Chemical Physics, 143 (6), 2015

Institutional Repository

journal article

© 2015 AIP Publishing