Building Highly Efficient Nanofiltration Membrane with Enhanced Porosity via Incorporating Chitosan-Based Derivatives

Abstract Thin-film composite (TFC) nanofiltration membranes are widely employed for water treatment due to their effective retention of multivalent ions and organic contaminants. However, a significant challenge persists, with increased water permeability often compromising selectivity and structure stability. Here, we present the design and synthesis of highly efficient TFC membranes through the incorporation of water-soluble chitosan derivatives (carboxymethyl chitosan, CMCS, and arginine-modified chitosan, CSR) as a third component in the aqueous phase during interfacial polymerization. The chitosan derivatives, enriched with abundant active groups and strong charge properties, served as both additives and amino comonomers, optimizing the pore structure of the polyamide separation layer. The optimized CMCS/PIP-TFC membrane achieves a pure water permeance of 15.6 LMH/bar while maintaining >95% Na2SO4 rejection and exhibits a flux recovery rate > 99% after bovine serum albumin fouling. Molecular simulations reveal that the incorporated chitosan chains increase the fractional free volume from 14.3 to 29.9%. Additionally, the unique charge properties of chitosan endow the TFC membrane with remarkable antibacterial properties. This study provides new insights and strategies for the development of high-performance TFC membranes for industrial applications.