217e Diffusioosmosis of an Electrolyte Solution along a Plane Wall

Diffusioosmosis of an electrolyte solution is the electrokinetic flow involving a tangential concentration gradient of the electrolyte that interacts with a charged wall. Electrolyte solutions with a concentration gradient of order 1 M/cm along solid surfaces with a zeta potential of order kT/e (~25 mV; e is the charge of a proton, k is the Boltzmann constant, and T is the absolute temperature) can flow by diffusioosmosis at a velocity of order μm/s. The fluid motion caused by diffusioosmosis was analytically examined for the flow near a plane wall [1-6]. In these studies, however, the effect of lateral distributions of the counterions and co-ions on the local electric field induced by the imposed electrolyte concentration gradient in the tangential direction inside the electric double layer or the effect of the ionic convection on it caused by the diffusioosmotic flow was neglected.