Biofouling-resistant nanocellulose layer in hierarchical polymeric membranes: Synthesis, characterization and performance

In this study, we developed a hierarchical thin-film nanofibrous composite (TFNC) membrane with electrospun mat as substrate and hydrophilic nanocellulose as the antifouling barrier layer. We found that, due to the super-hydrophilic nature of the nanocellulose, the contact angle of the barrier layer (20−28°) decreased rapidly with time and reached nearly zero after a few seconds, whereby the membrane flux were remarkably higher (52L.m−2.h−1) than conventional polymeric membranes (4−14L.m−2.h−1) at a very low transmembrane pressure of 0.5 psi. In addition, the membrane surface was considerably more negatively-charged due to the high concentration of carboxylate groups, resulting in higher repulsive electrostatic forces between the barrier layer and the model foulant. As a result, the nanocellulose-based hierarchical membranes exhibited a lower fouling tendency (<10%) and a higher degree of protein rejection ratio compared with the conventional membranes (fouling tendency >30%). The effect of the nanocellulose layer thickness on the membrane fouling was also examined and it was demonstrated that the nanocellulose barrier layer thickness had a significant effect on the membrane fouling. The higher flux, lower fouling, and good rejection properties of this membrane system suggest nanocellulose is a promising barrier material for filtration membranes for water purification and other separation processes.