Current efficiency and selectivity reduction caused by co-ion leakage in electromembrane processes

Area of Science:

• Electrochemistry
• Chemical Engineering
• Materials Science

Background:

• Diffusion layers in electromembrane processes like electrodialysis (ED) and ion concentration polarization (ICP) affect membrane performance and energy efficiency.
• The diluate side diffusion layer is typically considered the main source of energy loss due to higher resistivity.
• The role of the concentrate side diffusion layer, particularly under convective flow, remains understudied.

Purpose of the Study:

• To investigate the impact of hydrodynamic convective flow on diffusion layer development in both diluate and concentrate streams during ICP desalination.
• To evaluate how convective flow in the concentrate stream influences current utilization and energy efficiency.
• To understand the mechanisms behind improved performance in high-current operation.

Main Methods:

• Experimental evaluation of ICP desalination under varying hydrodynamic convective flow conditions.
• Numerical modeling to simulate diffusion layer behavior and ion transport.
• Analysis of co-ion leakage and its correlation with current utilization.

Main Results:

• Higher convective flow in the concentrate stream significantly mitigates the drop in current utilization at high operating currents.
• This improvement is attributed to the suppression of co-ion leakage into the ion-exchange membrane.
• Both experimental data and numerical simulations confirm the role of convective flow in preventing leakage.

Conclusions:

• Hydrodynamic convective flow in the concentrate stream is crucial for enhancing current utilization and energy efficiency in ICP processes.
• Managing concentrate side diffusion layers offers a novel strategy for optimizing electromembrane system design.
• This research provides key insights for developing more energy-efficient desalination technologies.