WATER DEMINERALIZATION BY ELECTRODEIONIZATION WITH ION-EXCHANGE TEXTILES - COMPARISON WITH CONVENTIONAL ELECTRODIALYSIS

An electrodeionization process has been developed using ion-exchange t extiles (EDIT) instead of ion-exchange resins as currently used for th e production of ultrapure water. The study was carried out with a labo ratory pilot. Each membrane had an active area of 20 cm(2). Experiment s were performed with NaCl solutions at low concentration (from 3 to 3 00 mg.L-1) under various experimental conditions of flow rate and curr ent density. Different configurations of textile were tested: the dilu ate compartment of the electrodialysis stack was filled by either alte rnating layers of cation or anion-exchange textiles, or one layer of a mphoteric textile or bipolar textile. The best results were obtained w ith the latter configuration. The study allowed comparison of the perf ormances of EDIT with conventional electrodialysis (ED) in terms of cu rrent efficiency, demineralization ratio, and energy losses. A signifi cant improvement was obtained by introducing the textile. At the lowes t concentration (3 mg.L-1) and the highest flow rate (20.8 cm.s(-1)), the current and demineralization efficiencies were 150% higher with ED IT than with ED.