Biopolymer-supported thin-film composite membranes for reverse osmosis

Thin-film composite (TFC) membranes are employed in water treatment and thus significantly contribute to environmental remediation efforts. However, the underlying porous support membrane of TFC membranes is fabricated using large amounts of synthetic chemicals and organic solvents, which can adversely affect the environment. Hence, the development of ecofriendly porous membranes is necessary. In this study, we fabricated an all-biopolymer (chitosan (CHS) and cellulose)-based, mechanically robust porous membrane via aqueous solution processes. A porous CHS membrane was formed on cellulose-based traditional Korean paper as a backing fabric through pH-induced aqueous phase separation, followed by chemical crosslinking with pyrogallol, a plant-derived natural compound. The resultant highly porous (overall porosity = 68.1 ± 1.9%), mechanically reinforced CHS membrane had higher compaction resistance than commercial ultrafiltration membranes under hydrodynamically pressurized conditions (up to 15.5 bar). The prepared CHS membrane was subsequently used as a support for fabricating a TFC membrane via interfacial polymerization. The CHS-supported TFC membrane exhibited competitive reverse osmosis performance (water permeance = 1.68 ± 0.13 L m⁻² h⁻¹ bar⁻¹, NaCl rejection = 99.4 ± 0.1%) and long-term durability. The CHS membrane also showed excellent biodegradability, which enabled its ecofriendly disposal. Our study provides a sustainable platform for fabricating green membranes for various separation applications.