Demineralization by electrodialysis (ED) — separation performance and cost comparison for monovalent salts

The separation performance of K+ ions from KCl solution has been investigated by electrodialysis at constant voltage mode of operation as a function of flow rate and voltage scanned. TS-1-10 model electrodialysis equipment (Tokuyama) modified with rotameters was employed in experimental runs. The efficiencies of each unsteady state run were evaluated as specific power consumption with the electrical energy consumed only in stack. The separation performance of K+ ions was compared with that of Na+ ions.

A series of experiments was performed for removal of K+ ions from 0.01 M KCl solution within the range of potentials and flow rates chosen in the ED system of TS-1-10 model electrodialyzer (Tokuyama). The operation time was short when a high potential was applied. Specific power consumption increased with an increase in potential applied although it was not sensitive to the change in flow rate. The difference in the separation performances of NaCl and KCl was small when potential increased from 5 to 10 V. t E Idt Specific power consumption (SPC) = VD (1) The results are given in Fig. 5 as a function of flow rate and potential. It is clear that the potential applied greatly determines the SPC, whereas flow rate has negligible effect on it. As shown in Fig. 6, SPC data for both NaCl and KCl were similar.