1969 Volume 42 Issue 10 Pages 2741-2748
The effect of the condition of the diffusion-boundary layer in the ion-exchange membrane electrodialysis on the limiting-current density and on the relative transport numbers of ionic species with the same sign was studied. The limiting-current density in the laminar flow is approximately proportional to the first power of the concentration of the solution, the one-half power of the flow velocity of the solution, and, inversely, the one-half power of the membrane length in the direction of the flow. In the natural convection, it is proportional to the five-quarters power of the concentration of the solution. These experimental results agree with the relation of the equations of the limiting-current density for the electrode process. The change in the relative transport numbers of ionic species with the same sign, such as the magnesium and sodium ions or the sulfate and chloride ions, with the flow velocity, the concentration, and the temperature of the solution, the dimension of the membrane in the direction of the flow, and the current density were observed. The results were explained in terms of the change in the condition of the diffusion-boundary layer.
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