A Tool for a Spacer Material and Ion-exchange Membrane Compatibility Evaluation for Electrodialysis Module Design

Abstract

Electrodialysis is a widely used separation process for wastewater treatment, concentration of valuable products or production of organic acids. However, unwanted phenomena can occur during the operation of electrodialysis stacks such as internal leakage and/or external leak. In this study, a new simple tool is presented for testing materials suitable for use as spacers used in ED. This cell for testing leaks simulates ED stack and therefore allowing external leaks to be tested. Regarding tests results suitable materials for an ED scale-up can be chosen. Tests were done for three different pressures (1.5, 2 and 2.5 bar) and three different temperatures (25, 40 and 60 °C). To maintain the same conditions, the test cell was tightened by defined force in the range of 850 to 870 N. In the testing stack different combinations of membrane, and spacers were tested. It was found that with increasing temperature leaks decrease. Parameters that influence external leaks most are surface roughness, texture a hardness of ion-exchange membrane and spacer material.