Removal of calcium and magnesium hardness by electrodialysis

The separation performances of divalent ions (Ca2+ and Mg2+) by electrodialysis (ED) were compared using a constant voltage mode of operation. For the batch tests, TS-1-10 ED equipment was employed. During the experimental studies, the effects of electrical potential applied and flow rate of streams on the separation performance of each cation have been monitored by measuring the outlet concentrations of the dilute stream. The operation time was short when a high potential was applied. On the other hand, the effect of flow rate on separation performance was not so apparent. Specific power consumption increased with an increase in potential applied, although it was not sensitive to the change in flow rate.

Within the range of potentials and flow rates applied in ED system (TS-1-10), the separation performances of divalent ions (Ca2+ and Mg2+) were compared and a cost analysis was carried Fig. 3. Experimental data for dimensionless concentration of Mg2+ ions vs. time with respect to potential (left) and flow rate (right) out. The operation time was short when a high potential was applied. On the other hand, the effect of flow rate on separation performance was not so apparent. In addition, the operation time for divalent ions was found to be longer than that of monovalent ions. It was obtained that energy consumption (EC) was influenced by the potential applied. However, EC was not so sensitive to the change in flow rate. A model study based on the experimental data produced will be reported in the near future.