Mass Transfer in Electrodialysis

Mass transfer in electrolyte solutions is determined by the driving forces acting on the individual ions of the solution and by the friction of the ions with other components in the solution. The driving forces can be expressed by gradients in the electrochemical potential of individual components. The friction that has to be overcome by the driving force can be expressed by the ion mobility or diffusivity.

To describe the mass transport in a system, thermo-dynamic and kinetic parameters must be mathematically related. Several relations are described in the literature. The one most frequently used is the Nernst-Planck equation which describes transport of ions under isobaric and isothermal conditions in an ion exchange membrane as follows:

The concentration of individual ions is related to that of the salt by the stoichiometric coefficient v which determines into how many ions a salt will dissociate in the solution. Thus:

Another assumption in electrodialysis is that electrical charges are transported exclusively by ions. Thus:

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Solar Panel Basics

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