The Driving Force and Fluxes in Electromembrane Processes

The driving force for the flux of a component in electromembrane processes is a gradient in their electrochemical potential which is given at constant temperature by  

Here dp. , dr) , dp. , din au dtp and dp are the gradients of the electrochemical potential, the chemical potential, the activity, the electrical potential and of the hydrostatic pressure, F is the Faraday constant and R the gas constant, and Tthe temperature. 

The mass transport in electromembrane processes at constant pressure and temperature can be described as a function of the driving force by a phenomenological equation [17], that is,  

Lu is a phenomenological coefficient relating the driving force to the corresponding flux, the subscripts i and k refer to various components in the system. 

Assuming an ideal solution in which the activity of a component is identical to its concentration and no kinetic coupling occurs between individual fluxes, Equation 5.8 becomes identical with the Nernst-Planck flux equation [18], which is given by  

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