Mass transfer investigations in electrodeionization processes using the microcolumn technique
Résumé
Electrodeionization, consisting of a combination of ion exchange to electrodialysis, allows the production of ultrapure water. Various transport and transfer processes are involved in the overall process, and in spite of its development at industrial scale, the fundamental aspects have been scarcely investigated up to now. We suggest in this paper the use of the microcolumn technique, which was proposed formerly for ion-exchange applications, for investigations of mass transfer processes involved. For the case of dilute copper chloride solutions, the leakage of the 15 mm high microcolumn was measured, depending on the resin nature—inert or ion-exchange materials—and the current level in a pulsed electrical mode. Models have been developed to extract values of four kinetics parameters. The results of the didactic work show that ion exchange and migration rates with ion-exchange resins, are far larger than mass transfer rates from the solution surrounding the packed bed, through the membranes. Particle–particle and particle–membrane contacts, in the presence of the liquid, are shown to be of major importance in ion transport in the cell.