Water Demineralization by Electrodeionization with Ion-Exchange Textiles. Comparison with Conventional Electrodialysis

An electrodeionization process has been developed using ion-exchange textiles (EDIT) instead of ion-exchange resins as currently used for the production of ultra-pure water. The study was carried out with a laboratory pilot. Each membrane had an active area of 20 cm 2 . Experiments were performed with NaCl solutions at low concentration (from 3 to 300 mg-L %minus;1 ) under various experimental conditions of flow rate and current density. Different configurations of textile were tested: the diluate compartment of the electrodialysis stack was filled by either alternating layers of cation or anion-exchange textiles, or one layer of amphoteric textile or bipolar textile. The best results were obtained with the latter configuration. The study allowed comparison of the performances of EDIT with conventional electrodialysis (ED) in terms of current efficiency, demineralization ratio, and energy losses. A significant improvement was obtained by introducing the textile. At the lowest concentration (3 mg.L −1 ) and the highest flow rate (20·8 cm.s −1 ), the current and demineralization efficiencies were 150% higher with EDIT than with ED.