Modelling the Performance of Electrically Conductive Nanofiltration Membranes

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Electrically conductive membranes are stimuli-responsive materials enabling adjustable selectivity for charged species via surface potential manipulation.
• Electrical assistance aids in overcoming the selectivity-permeability trade-off, facilitating neutral solvent passage while managing charged solutes.
• Understanding charge interactions is crucial for optimizing nanofiltration processes.

Purpose of the Study:

• To propose a mathematical model for the nanofiltration of binary aqueous electrolytes using electrically conductive membranes.
• To investigate the influence of simultaneous chemical and electronic surface charges on solute exclusion.
• To analyze the role of the potential of zero charge (PZC) in membrane selectivity.

Main Methods:

• Development of a mathematical model incorporating steric and Donnan exclusion mechanisms.
• Consideration of both chemical and electronic surface charges affecting charged species.
• Application of the model to experimental data from PANi-PSS/CNT and MXene/CNT nanofiltration membranes.

Main Results:

• Membrane rejection is minimized at the potential of zero charge (PZC), where electronic and chemical charges neutralize.
• Rejection increases with deviations of surface potential from the PZC in both positive and negative directions.
• The model successfully describes experimental data for salt and anionic dye rejection.

Conclusions:

• The proposed model provides insights into the selectivity mechanisms of conductive membranes.
• Electrical charge compensation at the PZC is a key factor in minimizing solute rejection.
• The model can be utilized for describing and optimizing electrically enhanced nanofiltration processes.