| Abstract |
| High-recovery reverse osmosis (RO) processes for wastewater reuse inevitably generate RO concentrate (ROC) with elevated total dissolved solids, creating a concentrated residual stream that requires further treatment or resource recovery. Electrodialysis (ED) is a promising post-treatment option for ROC management; however, its economic feasibility is largely governed by the performance and cost of ion-exchange membranes (IEMs), which account for 30-40% of the process cost and are predominantly supplied by a limited number of foreign manufacturers. Therefore, evaluating the performance of domestically developed IEMs under realistic ROC treatment conditions is important for assessing their potential as cost-effective alternatives to commercially available foreign membranes. This study quantitatively compared domestically developed cation-and anion-exchange membranes (A) with commercial foreign membranes (B) under identical operating conditions using ROC generated at 90% recovery from a municipal wastewater reuse plant. The physicochemical properties of the membranes were characterized, and their area resistance was evaluated in 0.5 M and 0.05 M NaCl solutions and in ROC. Their limiting current density (LCD) was also determined at linear velocities ranging from 7.3 to 18.8 cm/s. In addition, batch concentration performance was evaluated under varying applied voltages (1.5-2.7 V/cell pair) and electrode-solution concentrations (Na2SO4, 1-7 wt.%) were evaluated. The domestic membranes were thinner (95 ?m vs. 110 ?m), exhibited higher ion-exchange capacities (CEM > 1.3 and AEM > 2.0 meq/g), and had lower water content compared to the foreign membranes. They also exhibited substantially lower area resistance in ROC, with the CEM showing approximately half the resistance of its foreign counterpart (13.2 vs. 28.0 Ω·cm²). The LCD was consistently higher for the domestic membranes across all tested linear velocities (20.7-30.1 vs. 17.0-25.1 mA/cm²), indicating a greater allowable current density before concentration polarization became limiting. In batch concentration experiments, the domestic membranes achieved concentration rates comparable to those of the foreign membranes while requiring a lower optimal electrode-solution concentration (1 wt.% vs. 2 wt.%). Given that their unit price was approximately one-third that of the foreign product, the domestic IEMs demonstrated strong potential as a practical and economically viable alternative for ED-based ROC reuse. |
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| Key Words |
| Electrodialysis, ED, Reverse osmosis, RO, RO concentrate, Ion-exchange membrane, Wastewater, 전기투석, 역삼투막, RO 농축수, 이온교환막, 하폐수 |
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