Electrochemical Transport in Bulk Fluid

The analysis of mass transport by diffusion under chemical (dCldx) and by migration under electrical (dd ldx) gradients in dilute solutions—for which the interactions between individual species can be neglected—is described by the Nemst-Planck (Eq. 2.1) and the Poisson s (Eq. 2.2), together referred to as the PNP equations  

For many electrochemical systems, the local electroneutrality condition is used, which sets the left-hand side of Equation 2.2 to zero for zero charge density. The mathematical implication is then that the electrical potential satisfies the Laplace equation (V = 0), hence the uniform concentration distribution and uniform 

The charge density accumulation cannot be neglected for interphase layers such as the electrical double layer. Using a nondimensionalized form of Equation 2.2, it was shown that the electroneutrality condition is a direct result of the Debye screening length, where the ratio of the Debye length Xx, to the field length L is described as follows (Eq. 2.3) (Chu, 2005)  

4 ELECTROCHEMICAL TRANSPORT IN CLAYS IN THE DIRECTION OE APPLIED ELECTRIC FIELD 

Electrically induced migration of ions and water is a proven method of externally forced mass transport in clay soils for contaminant remediation purposes (Pamukcu and Wittle, 1992 Acar and Alshawabkeh, 1993,1996 Lageman, 1993 Probstein and 

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