Highly flexible free-standing bacterial cellulose-based filter membrane with tunable wettability for high-performance water purification.

Water purification has always been a critical yet challenging issue. In this study, an organic-inorganic composite membrane was developed using 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized bacterial cellulose (BC) nanofibers and hydroxyapatite nanowires (HAPNW) with tunable wettability for advanced membrane separation applications. The resulting free-standing TEMPO-BC/HAPNW filter membrane exhibited strong mechanical strength, high flexibility, exceptional deformability, and a high pure water flux of up to 800 L·m·h due to its porous architecture and inherent hydrophilicity. Additionally, the filter membrane demonstrated long-term high rejection efficiency towards TiO nanoparticles and methylene blue through size exclusion and electrostatic interaction. Notably, the surface wettability of the composites switched to being hydrophobic and lipophilic after in situ modification, enabling superior separation of various organic solvents and oils while maintaining cycle stability. This work presents a novel biomass-derived filter membrane for efficient and sustainable wastewater treatment with high performance, easy scale-up, and green regeneration.