Self-generation of concentration gradients of divalent cations in commercial bentonite membrane during ultrafiltration

Donnan-ion hydration model to estimate the electroosmotic permeability of clays

“…the first is usually of the order of tens of mV m -1 and the second of tens of V m -1 , so there are three orders of magnitude difference between them. As an example of this difference, Chatterji[61] identifies a gradient due to the charge of clay of 0.645 V m -1 for an unusually high concentration gradient of 771 mol m -4 . However, most of the electrokinetic soil remediation tests are performed using gradients of around 100 V m -1[13].Applying the definition of the effective ionic mobility, Le,i u [m 2 V -1 s -1 ] [62-64] to define the velocity of the ion in soil pores under an electric field as L into account that the total molar flux is the sum of the molar flux evaluated in each functional level, the volumetric electroosmotic flux [m is the molar mass of water Ni is the number of water molecules hydrating the i-th ionic species and TOT ( , ) K K e SSA = is a dimensionless function of the internal ordering of clay given by the total void ratio, TOT e , and the activity of the clay given by its specific surface area.…”