Role of the membrane surface in concentration polarization at ion-exchange membrane

✍ Scribed by I. Rubinstein; E. Staude; O. Kedem

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 934 KB
• Volume: 69
• Category: Article
• ISSN: 0011-9164
• DOI: 10.1016/0011-9164(88)80013-4

✦ Synopsis

A thm convection-free cell was constructed for the characterlzatlon of cation-exchange membranes, with CuS04 solutions confined between thick copper electrodes. Current-voltage curves were recorded for several homogeneous membranes. The limiting current, 1.e. the flat portion of the curve, was 1.5-4 times lower than the theoretical prediction. At high voltage the current mcreases approximately linearly above its limiting value. Onset of noise and noise frequency were determined. It was suggested that the ion conductance of the membrane surface 1s not uniform. This inhomogeneity decreases the avallable area and, at high voltage, gives rise to local mixing of the unstirred layer by electroconvection.

High limiting current was observed with a composite membrane comprlsmg a porous heterogeneous layer and a highly permselectlve dense homogeneous layer (sulfonated polysulfone).

This may be due to electroconvectlon in the porous part of the layered structure. The drastic dlfference of polarlzatlon at homogeneous sulfonated polysulfone membranes and at the composite membrane was confirmed m a laboratory electrodialysls stack.