Multifunctional polyelectrolyte multilayers as nanofiltration membranes and as sacrificial layers for easy membrane...

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Ultra-filtration (UF) membranes are prone to fouling, reducing performance and lifespan.
• Developing membranes with enhanced separation capabilities and self-cleaning properties is crucial for water treatment.
• Polyelectrolyte multilayers (PEMs) offer tunable properties for membrane surface modification.

Purpose of the Study:

• To investigate the modification of UF membranes with polyelectrolyte multilayers (PEMs) for dual nanofiltration (NF) and sacrificial layer applications.
• To optimize PEM coating and removal conditions for effective membrane cleaning.
• To evaluate the separation performance and fouling removal efficiency of the modified membranes.

Main Methods:

• Coating of charged UF membrane supports with weak polyelectrolytes (poly(allyl amine) hydrochloride and poly(acrylic acid)).
• Characterization of PEM-coated membranes using optical reflectometry, zeta potential measurements, and pure water permeation tests.
• Evaluation of solute rejection (NaCl, sulfamethoxazole, SO3(2-)) to assess NF capability.
• Fouling experiments with silica nanoparticles and assessment of sacrificial layer cleaning efficiency via membrane resistance measurements.

Main Results:

• PEM coating increased membrane resistance and altered zeta potential, indicating successful modification.
• PEM membranes exhibited nanofiltration characteristics, rejecting >60% of sulfamethoxazole and SO3(2-) while allowing NaCl passage.
• The sacrificial PEM layer effectively removed silica nanoparticle foulants with a low-pressure backwash, restoring membrane performance close to pristine levels.
• Recoating allowed for recovery of original membrane performance, with fewer layers needed for cleaning compared to model surfaces.

Conclusions:

• PEMs provide a dual function for UF membranes, enabling both nanofiltration and sacrificial cleaning.
• The sacrificial layer approach, particularly with backwashing capability, significantly improves membrane cleanability and extends operational life.
• This modification offers a promising strategy for developing robust and easily maintainable membrane systems for various applications.