Return flow ion concentration polarization desalination: A new way to enhance electromembrane desalination

• Published in: Water research (Oxford) Vol. 159; pp. 501 - 510
• Main Authors: Yoon, Junghyo, Do, Vu Q., Pham, Van-Sang, Han, Jongyoon
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.08.2019
• Subjects: Desalination; Electrodialysis; Ion concentration polarization; Return-flow; Unipolar; Unipolar; Ion concentration polarization; Desalination; Return-flow; Electrodialysis
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2019.05.042

In electromembrane desalination processes such as electrodialysis (ED) and ion concentration polarization (ICP) desalination, ion-depleted boundary layers constitute the desalted, product stream, yet also cause high resistivity and voltage drop. Directly manipulating fluid flow streams is a new method to break this fundamental trade-off for electromembrane desalination. In this work, we are introducing a novel electromembrane desalination architecture that allows a feed stream to return to the feed inlet side of the membrane (hereby named as return-flow (RF) architecture) to improve the energy efficiency by re-distributing and controlling the depleted boundary layer, even at high current values. The technical feasibility of this idea was examined in ICP desalination process (RF-ICP) with a wide range of feed salinity from 10 to 70 g/L. For a partial desalination, RF-ICP (∼75 cm2 of membrane area) has achieved similar power consumption compared to batch-ED with 3 times bigger membrane area (200 cm2) with a higher area efficiency for salt removal, which translates into lower optimal desalination cost. The techno-economic analysis of RF-ICP have been performed for the treatment of 70 g/L brine waste. For partial desalination of 70 g/L brine down to 35 g/L, RF-ICP desalination achieved overall water cost as low as $2.57/m3 ($0.41/barrel). This could translate into reduction in total water cost up to 31% for zero brine release scenarios, depending on the concentrated brine treatment cost. These results show that return-flow architecture can improve the performance of electromembrane desalination, enabling more flexible water treatment for many real-world applications. •A novel channel architecture, RF-ICP, was first developed for electromembrane desalination.•RF-ICP allowed the feedwater stream to return to the feed inlet side of the membrane.•RF-ICP improved the energy efficiency by re-distributing and controlling the depleted boundary layer.•RF-ICP was adopted for the ICP desalination with a wide range of feed salinity (10–70 g/L).•The techno-economic analysis was performed for partial desalination of brine.