Porous thin film barrier layers from 2,3-dicarboxylic acid cellulose nanofibrils for membrane structures

To fabricate a strong hydrophilic barrier layer for ultrafiltration (UF) membranes, 2,3-dicarboxylic acid cellulose nanofibrils with high anionic surface charge density (1.2 mekv/g at pH 7) and a width of 22 ± 4 nm were used. A simple vacuum filtration method combined with a solvent exchange procedure resulted in a porous layer with a thickness of ∼ 0.85 μm. The fabricated membranes reached high rejection efficiencies (74-80%) when aqueous dextrans up to 35-45 kDa were filtrated to evaluate the molecular weight cut-offs (MWCO). A linear correlation between the barrier layer thickness and the flux rate was observed in all tested cases. Further optimization of the barrier layer thickness can lead to an even more effective structure.