Composites based on electrospun fibers modified with cellulose nanocrystals and SiO2 for selective oil/water separation

Membranes for water remediation require structural stability, efficient operation, and durability. In this work, we used cellulose nanocrystals (CNC) to reinforce hierarchical nanofibrous membranes based on polyacrylonitrile (PAN). Hydrolysis of the electrospun nanofibers (H-PAN) enabled hydrogen bonding with CNC and provided reactive sites for grafting cationic polyethyleneimine (PEI). In a further modification, anionic silica particles (SiO2) were adsorbed on the fiber surfaces, obtaining CNC/H-PAN/PEI/SiO2 hybrid membranes, which developed swelling resistance (swelling ratio of 6.7 compared to 25.4 measured for a CNC/PAN membrane). Hence, the introduced hydrophilic membranes contain highly interconnected channels, they are non-swellable and exhibit mechanical and structural integrity. By contrast with untreated PAN membranes, those obtained after modification displayed high structural integrity and allowed regeneration and cyclic operation. Finally, wettability and oil-in-water emulsion separation tests demonstrated remarkable oil rejection and separation efficiency in aqueous media.