Fabrication of chitin membranes for dye/salt separation

Biopolymer-based membranes are a promising route to sustainable wastewater treatment, yet truly green membranes combining sustainability, performance, and durability remain challenging. Chitosan (CS), though widely used, suffers from poor pH stability. Herein, we demonstrate the first entirely green chitin (CT)-based nanofiltration (NF) membrane by forming a dense asymmetric CS membrane via aqueous phase separation, followed by acetylation. The resultant CT membrane showed high dye/salt selectivity under both single- and multi-solute conditions, outperforming reported green membranes. The CT membrane also exhibited excellent mechanical strength and pH stability, thereby enabling stable operation across various pH. while showing exceptional biodegradability. This work offers a sustainable strategy for high-performance, durable, and entirely green membranes.