Production of high resistivity water by electrodialysis. Influence of ion-exchange textiles as conducting spacers

Production of high resistivity water was investigated by electrodialysis (E D) using either inert or conducting spacers. Ion-exchange textiles were use d as conducting spacers. Experiments were performed on a preindustrial scal e with a pilot consisting of nine two-compartment cells, each membrane havi ng an effective area of 176 cm(2). Three configurations of the ED stack wer e investigated for the dilution compartment: EDIT-(2) with a 2-mm thick ion -exchange textile, and ED-(2) or ED-(0.4), with a 0.4-mm thick inert spacer inserted between 2 or 0.4 mm thick dilution compartments, respectively. Th e textile induces a moderate increase in the pressure drop between the inle t and outlet of the stack. The performances of the different processes were compared under various experimental conditions of pH, nitrogen bubbling th roughout the feed solution, flow rate, and current density. The results sho w that for an inlet conductivity of 10-15 mu S.cm(-1), a flow rate of of 2. 2 x 10(-5) m(3) . s(-1), and an applied voltage of 80 V, an outlet conducti vity of 0.4 mu S.cm(-1) was obtained with the EDIT process, while no value lower than 5 mu S . cm(-1) was obtained with the ED process using both stac ks.