Key Takeaways & Executive Findings
- •• • Click chemistry conversion of PAN to PAN-N increased water flux from 0.9233 to 1.232 L·(m2·h·kPa)−1 and BSA rejection from 69.23% to 82.4%, demonstrating that tetrazole functionalization enhances membrane hydrophilicity and separation performance. • • Hydrophilic modification with iodoacetic acid (PAN-N-IA) achieved the highest water flux of 1.7347 L·(m2·h·kPa)−1 and BSA rejection of 93.57%, representing a 88% increase in flux and 35% increase in rejection over pristine PAN, critical for high-efficiency water treatment. • • Anti-fouling performance followed the order PAN-N-CSA > PAN-N-IA > PAN-N-IH > PAN-N-IAM > PAN-N > PAN, with PAN-N-CSA and PAN-N-IA showing total fouling indices of 56.1% and 58.47%, respectively, and irreversible fouling indices below 11.5%, indicating superior fouling resistance and extended membrane lifespan. • • The introduction of hydrophilic groups (carboxyl, sulfonic, hydroxyl, amide) via covalent grafting promotes a hydration layer on the membrane surface, effectively reducing protein adhesion and fouling, which is essential for reducing operational costs in industrial water treatment.
Abstract
Polyacrylonitrile (PAN) ultrafiltration membranes are widely used in water treatment, yet their anti-fouling performance remains a challenge. In this work, PAN was first reacted with sodium azide via click chemistry to synthesize 1,2,3,4-tetrazolium polyacrylonitrile (PAN-N). Subsequently, PAN-N was reacted with iodoacetamide (IAM), 2-iodoethanol (IH), iodoacetic acid (IA), and chlorosulfonic acid (CSA) to introduce hydrophilic groups, and anti-fouling PAN ultrafiltration membranes were fabricated via phase inversion. The membranes were characterized by Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance, X-ray diffraction, scanning electron microscopy, and contact angle measurements. Results showed that the PAN-N membrane exhibited superior performance to pristine PAN, with water flux increasing from 0.9233 to 1.232 L·(m2·h·kPa)−1 and bovine serum albumin (BSA) rejection from 69.23% to 82.4%. Hydrophilic modification further enhanced performance; the PAN-N-IA membrane achieved the highest water flux of 1.7347 L·(m2·h·kPa)−1 and rejection of 93.57%. Anti-fouling tests revealed that modified membranes followed the order: PAN-N-CSA > PAN-N-IA > PAN-N-IH > PAN-N-IAM > PAN-N > PAN. PAN-N-CSA and PAN-N-IA showed comparable anti-fouling performance, with total fouling indices of 56.1% and 58.47%, reversible fouling indices of 47.17% and 46.97%, and irreversible fouling indices of 8.97% and 11.47%, respectively. This work demonstrates that PAN-N-IA membranes combine high flux, high rejection, and excellent anti-fouling properties, making them promising for water treatment applications.
1. Introduction
Polyacrylonitrile (PAN) ultrafiltration membranes are widely adopted in industrial water treatment due to their excellent thermal stability, mechanical strength, and chemical resistance. However, their intrinsic hydrophobicity leads to severe membrane fouling, particularly by proteins and other organic matter, resulting in flux decline, increased energy consumption, and frequent cleaning requirements. Conventional surface modification strategies, such as physical blending or coating, often suffer from poor stability and leaching of modifiers, limiting long-term performance. The development of robust anti-fouling membranes with high permeability and selectivity remains a critical bottleneck for sustainable water treatment technologies.
This study addresses this challenge by employing click chemistry to covalently anchor tetrazole groups onto PAN, followed by further functionalization with hydrophilic moieties (carboxyl, hydroxyl, sulfonic, and amide groups). This approach ensures stable chemical bonding and uniform distribution of hydrophilic groups, enhancing membrane hydrophilicity and fouling resistance without compromising mechanical integrity. The systematic evaluation of water flux, BSA rejection, and fouling indices provides quantitative evidence of performance improvements, offering a viable pathway for fabricating high-performance ultrafiltration membranes for industrial applications.
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LU Jingqiong, ZHANG Xingpeng, WANG Hui, ZHANG Jing, ZHAO Jinguo, GAO Chengyun, ZHAO Xudong (2026). Preparation and Performance of Anti-fouling Polyacrylonitrile Ultrafiltration Membranes. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2025021902
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Frequently Asked Questions
What is the long-term stability of the hydrophilic modification under continuous operation and chemical cleaning?
The study does not provide long-term stability data. However, covalent grafting via click chemistry ensures strong chemical bonding, which typically resists leaching. Future studies should evaluate flux recovery after multiple fouling-cleaning cycles to confirm durability.
How does the water flux and rejection of PAN-N-IA compare to commercial ultrafiltration membranes?
PAN-N-IA achieved a water flux of 1.7347 L·(m2·h·kPa)−1 and BSA rejection of 93.57%. Commercial PAN membranes typically have fluxes in the range of 0.5-1.5 L·(m2·h·kPa)−1 and rejections of 80-95% depending on molecular weight cut-off. The modified membrane shows competitive or superior performance, but direct comparison requires standardized testing conditions.
What is the scalability of the click chemistry modification process for industrial production?
Click chemistry reactions are generally scalable, but the use of sodium azide and organic solvents requires careful handling and waste management. The reaction conditions (temperature, time, solvent) need optimization for large-scale production. Cost analysis is not provided, but the additional steps may increase membrane cost, which must be justified by improved performance and lifespan.
What is the mechanism behind the improved anti-fouling performance of PAN-N-CSA and PAN-N-IA?
The introduction of sulfonic and carboxylic acid groups increases membrane surface hydrophilicity, promoting the formation of a hydration layer that reduces protein adsorption. The lower irreversible fouling indices (8.97% and 11.47%) indicate that most fouling is reversible and can be removed by simple hydraulic cleaning, leading to higher flux recovery.
How does the membrane performance vary with different feed water compositions, such as high salinity or varying pH?
The study only tested BSA as a model foulant. The effect of ionic strength and pH on membrane performance is not addressed. Future work should investigate the stability of the hydrophilic groups under extreme pH and high salinity conditions, as these are common in industrial wastewater.
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