Related Experiment Video
Updated: Aug 4, 2025
Synthesis of Hydrogels with Antifouling Properties As Membranes for Water Purification
Published on: April 7, 2017
Microporous Polyethersulfone Membranes Grafted with Zwitterionic Polymer Brushes Showing Microfiltration Permeance
Ji Qin1, Eric Ziemann1, Edo Bar-Zeev1
1Zuckerberg Institute for Water Research, The Jacob Blaustein Institutes for Desert Research of the Ben-Gurion University of the Negev, Campus Sde Boker, Midreshet 84990, Israel.
Abstract:
Virus removal from water using microfiltration (MF) membranes is of great interest but remains challenging owing to the membranes' mean pore sizes typically being significantly larger than most viruses. We present microporous membranes grafted with polyzwitterionic brushes (N-dimethylammonium betaine) that combine bacteriophage removal in the range of ultrafiltration (UF) membranes with the permeance of MF membranes. Brush structures were grafted in two steps: free-radical polymerization followed by atom transfer radical polymerization (ATRP). Attenuated total reflection Fourier transform infrared (ATR-FTIR) and X-ray photoelectron (XPS) verified that grafting occurred at both sides of the membranes and that the grafting increased with increasing the zwitterion monomer concentration. The log reduction values (LRVs) of the pristine membrane increased from less than 0.5 LRV for T4 (∼100 nm) and NT1 (∼50 nm) bacteriophages to up to 4.5 LRV for the T4 and 3.1 LRV for the NT1 for the brush-grafted membranes with a permeance of about 1000 LMH/bar. The high permeance was attributed to a high-water fraction in the ultra-hydrophilic brush structure. The high measured LRVs of the brush-grafted membranes were attributed to enhanced bacteriophages exclusion from the membrane surface and entrapment of the ones that penetrated the pores due to the membranes' smaller mean pore-size and cross-section porosity than those of the pristine membrane, as seen by scanning electron microscopy (SEM) and measured using liquid-liquid porometry. Micro X-ray fluorescence (μ-XRF) spectrometry and nanoscale secondary ion mass spectrometry showed that 100 nm Si-coated gold nanospheres accumulated on the surface of the pristine membrane but not on the brush-coated membrane and that the nanospheres that penetrated the membranes were entrapped in the brush-grafted membrane but passed the pristine one. These results corroborate the LRVs obtained during filtration experiments and support the inference that the increased removal was due to a combined exclusion mechanism and entrapment. Overall, these microporous brush-grafted membranes show potential for use in advanced water treatment.
Insights
New microporous membranes grafted with polyzwitterionic brushes effectively remove viruses from water. These advanced membranes combine virus removal capabilities with high water flow, offering potential for improved water treatment technologies.
Area of Science:
- Materials Science
- Environmental Engineering
- Nanotechnology
Background:
- Microfiltration (MF) membranes struggle with virus removal due to pore sizes larger than most viruses.
- Existing water treatment methods require more efficient and effective virus removal strategies.
Purpose of the Study:
- To develop novel microporous membranes with enhanced virus removal capabilities.
- To investigate the performance of polyzwitterionic brush-grafted membranes for water purification.
- To combine the high permeance of MF membranes with the virus removal efficiency of ultrafiltration (UF) membranes.
Main Methods:
- Grafting polyzwitterionic brushes onto microporous membranes using a two-step polymerization process (free-radical polymerization followed by atom transfer radical polymerization - ATRP).
- Characterization of grafted membranes using Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy and X-ray Photoelectron (XPS) spectroscopy.
- Evaluation of virus removal efficiency using bacteriophages (T4 and NT1) and assessment of membrane permeance.
- Analysis of membrane structure and porosity using Scanning Electron Microscopy (SEM) and liquid-liquid porometry.
- Tracking nanoparticle behavior on pristine and grafted membranes using Micro X-ray Fluorescence (μ-XRF) spectrometry and nanoscale secondary ion mass spectrometry.
Main Results:
- Brush-grafted membranes demonstrated significant bacteriophage removal, achieving up to 4.5 log reduction values (LRVs) for T4 and 3.1 LRVs for NT1.
- The modified membranes maintained high permeance (approximately 1000 LMH/bar) due to their ultra-hydrophilic brush structure.
- Enhanced virus removal was attributed to a combination of surface exclusion and pore entrapment mechanisms, confirmed by nanoparticle tracking experiments.
Conclusions:
- The developed polyzwitterionic brush-grafted microporous membranes offer a promising solution for efficient virus removal in water treatment.
- These membranes bridge the performance gap between MF and UF, providing high flux and effective pathogen removal.
- The findings support the potential application of these advanced membranes in next-generation water purification systems.
