CO₂-Responsive Dual-Charge-Switchable Membranes for Protein Foulant Cleaning.

Area of Science:

• Materials Science
• Environmental Science
• Chemical Engineering

Background:

• Conventional CO2-responsive membranes have limited single-charge switching, hindering electrostatic foulant removal.
• Effective membrane cleaning is crucial for water purification efficiency and longevity.

Purpose of the Study:

• To develop CO2-responsive poly(ether sulfone) (PES) ultrafiltration membranes with a dual charge-switchable surface.
• To achieve environmentally friendly and chemical-free membrane cleaning through gas-triggered surface charge modulation.

Main Methods:

• Nonsolvent-induced phase separation (NIPS) method was employed to incorporate an amphoteric diblock copolymer into PES membranes.
• The isoelectric point (IEP) of the copolymer was tuned to enable reversible surface charge switching between positive and negative states.
• Alternating bubbling of CO2 and N2 gases was used to trigger pH changes and modulate membrane surface charge.

Main Results:

• The prepared membranes exhibited reversible surface charge switching from positive to negative under alternating CO2 and N2 bubbling.
• Increasing copolymer content enhanced the presence of amphoteric chains on the membrane surface.
• Protein-fouled membranes were effectively cleaned using water with alternating gas bubbling, demonstrating efficient electrostatic repulsion-based cleaning.
• The gas-triggered cleaning efficiency was comparable to conventional acid/alkaline cleaning and showed stability over multiple cycles.

Conclusions:

• The developed dual charge-switchable membranes offer a promising approach for sustainable and chemical-free membrane cleaning.
• This technology has significant potential for improving the performance and reducing the environmental impact of ultrafiltration processes.