ELECTROKINETIC INSTABILITY OF SOLUTION IN A PLANE-PARALLEL ELECTROCHEMICAL-CELL

The current passage through a binary electrolyte solution contained in a plane-parallel cell is considered, The cell is formed by two identi cally ideal selective ion-exchange membranes. Nonetheless, the solutio n of the problem can also be employed for a cell made by two uniformly reversible electrodes, Using the corresponding boundary conditions it is taken into account that the solution can be involved in an electro - and capillary osmotic slipping at the membrane (electrode)/soIution interface provided the tangential gradients of the electrolyte concent ration and/or the potential are close to the interface, The analysis o f the stability of the well-known one-dimensional solution correspondi ng to linear concentration distribution in the cell is carried out. Th e analysis shows that the slipping gives rise to a hydrodynamic instab ility of the one-dimensional solution when colons have sufficiently lo w diffusion coefficients in the order of about 10(-6) cm(2) s(-1). Und er this condition convective flows with periodical structure: may aris e when current approaches the limiting value. (C) 1996 Academic Press, Inc.