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Merging Ion Concentration Polarization between Juxtaposed Ion Exchange Membranes to Block the Propagation of the Polarization Zone
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Visualizing Enhanced Microfluidic Electromembrane Desalination Using Nafion-Coated Heterogeneous Ion-Exchange
Hyunwoo Choi1, Bonseung Ku1, Seokhee Han2
1Department of Mechanical and Automotive Engineering, Kongju National University, Cheonan 31080, Republic of Korea.
Molecules (Basel, Switzerland)
|February 27, 2026
Summary
Coating heterogeneous ion-exchange membranes with Nafion enhances desalination by amplifying electro-convection (EC) vortices. This surface modification boosts current efficiency and salt removal, demonstrating a new path for high-performance water purification.
Area of Science:
- Membrane science
- Electrochemistry
- Fluid dynamics
Background:
- Heterogeneous ion-exchange membranes (IEMs) offer cost-effectiveness but exhibit low electrochemical efficiency due to surface imperfections.
- Surface modification with homogeneous ionomers is a strategy to improve IEMs, but its direct impact on electro-hydrodynamic behavior and desalination performance is not well understood.
Purpose of the Study:
- To visualize and quantify the performance enhancement of Nafion-coated heterogeneous cation exchange membranes (CEMs) using a microfluidic platform.
- To investigate the relationship between surface modification, electro-convection (EC), and desalination performance.
Main Methods:
- Utilized a microfluidic platform for direct visualization and quantification of electro-hydrodynamic phenomena.
- Employed Nafion coating on heterogeneous CEMs as a surface modification strategy.
- Conducted continuous desalination experiments to assess performance metrics.
Main Results:
- Nafion coating significantly amplified electro-convection (EC) vortices, contrary to conventional theories linking EC to hydrophobicity.
- Visualizations revealed the coating acts as an electrical nozzle, focusing the electric field and promoting vortex growth.
- The coating suppressed parasitic water-splitting reactions by sealing catalytic sites.
- Desalination experiments showed a 32% increase in current efficiency and an 18% increase in salt removal ratio compared to bare membranes.
Conclusions:
- Controlled hydrodynamic instability induced by surface modification is a key factor for high-efficiency desalination.
- Nafion coating on heterogeneous CEMs enhances desalination performance through amplified EC and suppression of parasitic reactions.
- This study provides visual evidence and quantification of performance enhancement via surface modification, offering a new strategy for membrane-based water treatment.
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