Mechanically and structurally robust sulfonated block copolymer membranes for water purification applications.

Area of Science:

• Materials Science
• Environmental Science
• Chemical Engineering

Background:

• Ionic pollutants in water pose significant environmental and health risks.
• Nanofiltration membranes are crucial for water purification, but often face challenges with performance and stability.
• Developing advanced membranes with tailored properties is essential for effective water treatment.

Purpose of the Study:

• To demonstrate the effective removal of ionic pollutants using novel negatively charged nanofiltration membranes.
• To synthesize and characterize block copolymers with controlled architectures for membrane fabrication.
• To optimize membrane properties, including charge density, water permeability, and mechanical integrity, for water purification.

Main Methods:

• Synthesis of block copolymers comprising polystyrene (PS) and partially hydrogenated polyisoprene (hPI) with varied chain architectures.
• One-step cross-linking of hPI blocks and sulfonation of PS chains to create robust, functional membranes.
• Characterization of membrane performance using rejection tests for various ionic pollutants (divalent cations, NO3-, Na+).
• In situ neutron scattering experiments to confirm membrane nanostructures and water domain arrangements.

Main Results:

• The developed membranes exhibit excellent mechanical integrity and stable hydrophilic properties.
• Control over block copolymer architecture synergistically optimized membrane charge density and water permeability.
• The best performing membrane achieved >99% rejection of divalent cations, >85% NO3- rejection, and >87% Na+ rejection.
• In situ neutron scattering confirmed well-defined nanostructures and periodic water domains within the hydrated membranes.

Conclusions:

• Block copolymer-based nanofiltration membranes offer a promising approach for efficient ionic pollutant removal.
• Tailoring block copolymer architecture is a key strategy for simultaneously enhancing membrane charge, permeability, and mechanical strength.
• These advanced membranes demonstrate high performance in removing diverse ionic contaminants, indicating their potential for practical water purification applications.