Recent Progress of Zwitterionic Materials as Antifouling Membranes for Ultrafiltration, Nanofiltration, and Reverse Osmosis

Abstract

Numerous materials have been employed in the surface modification of membranes, including different polymers and nanomaterials over the years. The pernicious challenges of membrane separation include the trade-off between water permeability and solute rejection as well as fouling when it is tested under liquid conditions. Zwitterionic polymers have attracted wide interest due to their unique properties of containing both cationic and anionic groups while maintaining electroneutrality and high hydrophilicity. These zwitterionic polymers have been utilized as coating materials or grafted layers not only on the surfaces of porous membranes but also as thin film composite membranes. To illustrate, the membranes modified with this class of materials are capable of resisting foulants through two distinct mechanisms, which are the hydration layer formation and steric repulsion effect, showcasing their unique chemical properties. To bridge the gaps of the recent development of zwitterionic membranes and their relationships with foulants for targeted separation such as ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO), this critical review will first fundamentally classify the fouling into four categories according to their characteristics and fouling mechanisms, namely, inorganic foulants, nonmigratory foulants, spreadable foulants, and proliferative foulants. The antifouling strategies which are active antifouling and passive antifouling (e.g., fouling resistance and fouling release) will be summarized. Apart from that, the chemistry, morphology, and modification approaches of zwitterionic membranes including surface coating, surface grafting, and physical blending on targeted applications as well as the separation performance of the state-of-the-art membranes will be presented in detail. Lastly, the summary, outlook of major challenges and opportunities of the zwitterionic materials will be highlighted. It is anticipated that this review can generate a pathway to facilitate the next generation of zwitterionicbased membranes with superior separation performance for specific separation.

State-of-the-Art Organic- and Inorganic-Based Hollow Fiber Membranes in Liquid and Gas Applications: Looking Back and Beyond

“…Similarly, liquid separation membranes are also confined by the trade-off effect between permeability and solute rejection. Apart from that, the membranes are hindered by membrane fouling, which is the accumulation of particles, colloids, suspensions and microorganisms on or in the membrane [ 48 , 49 ]. Hollow-fiber unit is prone to fouling and plugging by particulate matter due to a relatively low free space between fibers as well as the small inside diameters [ 13 , 17 ].…”

Molecular simulations of zwitterlation-induced conformation and dynamics variation of glucagon-like peptide-1 and insulin

“…Some experimental work focuses on the anti-biofouling performance of zwitterionic peptides. 1,7,8,[25][26][27][28][29] They showed that zwitterionic peptide surface coatings could resist the adsorption of proteins. [30][31][32] Many anti-biofouling materials have shown their ability to protect proteins, ranging from polyethylene glycol [33][34][35][36][37][38][39][40][41] to synthetic zwitterionic polymers.…”

Poly(sulfur ylides): a new class of zwitterionic polymers with distinct thermal and solution behaviour

“…4,5 New applications of such zwitterionic polymers including antifouling coatings, drug delivery vesicles and phase separators make new forms of zwitterionic polymers indispensable. [6][7][8] Recent efforts to develop new polymeric zwitterionic structures have focused predominately on developing polybetaines with new forms of cations or anions. For example, Brown et al demonstrated that phosphonium cation bearing polybetaines are readily available forms zwitterionic polymers displacing the frequently used ammonium cation 9 .…”