Nanoporous Membranes from Bacterial Cellulose Derivatives for Water Treatment

Ultrafiltration (UF) membranes often suffer from fouling by microorganisms or biomolecules, causing reduced permeability, shorter life spans, and enhanced operating costs. This research aims to develop naturally derived and antifouling UF membranes for wastewater filtration using bacterial nanocellulose (BNC or BC) and its chemically modified derivatives, namely, oxidized BC (OBC), quaternary ammonium-containing BC (QABC), mixed zwitterionic BC (MZBC) and zwitterionic BC (ZBC) with various charge characteristics. A thin layer of the derivatized BC nanofibers with varied area density (90–1080 mg/m²) was deposited on commercial poly(vinylidene fluoride) microfiltration (PVDF-MF) membranes by vacuum filtration followed by oven drying, and chemical cross-linking with glutaraldehyde. The chemical functionality, zeta potential, surface morphology, and surface wettability of the fabricated membranes were characterized. The asymmetric membrane fabricated from the OBC had an area density of 1080 mg/m² (OBC1080) and exhibited filtration characteristics in terms of water permeability (0.70 ± 0.27 Lm^–2 h^–1 kPa^–1), bovine serum albumin (BSA) permeability (0.50 ± 0.11 Lm^–2 h^–1 kPa^–1), flux reduction (25 ± 13%), BSA rejection (98 ± 2%), and flux recovery (68 ± 16%) upon 3-cycled filtration equivalent to those of a commercial poly(ether sulfone) (PES) UF membrane. Its superior antiadhesion of both Gram-negative (Escherichia coli, E. coli) and Gram-positive (Staphylococcus aureus, S. aureus), bacteria to the PES-UF membrane was also demonstrated. It is strongly believed that the BC derivatives can potentially be further developed into naturally derived and antifouling materials for the fabrication of effective antifouling UF membranes for wastewater filtration in the future.