Phosphonium Modified Nanocellulose Membranes with High Permeate Flux and Antibacterial Property for Oily Wastewater Separation

Nanocellulose membranes could efficiently separate oily wastewater because of their super-hydrophilic and underwater super-oleophobic property and nano-porous structure. However, the practical application and storage of nanocellulose membranes is limited by their low water permeation flux and easy corrosion by bacteria, respectively. Herein, nanocellulose membranes with high permeate flux and antibacterial property were fabricated by grafting tetrakis(hydroxymethyl) phosphonium chloride (THPC) onto the surface of TEMPO-oxidized tunicate cellulose nanofibers (TCNFs) via esterification reaction. The introduction of THPC groups with tetrahedral structure on the surface of TCNFs significantly improved the pore size and interlayer space of nanocellulose membranes, resulting in an increase in water permeation flux. These THPC@TCNF membranes were super-hydrophilic and underwater super-oleophobic, which could effectively separate various oil/water nano-emulsions. Moreover, THPC@TCNF membranes possessed excellent durability, mechanical stability and cycling performance. Due to the presence of positively charged phosphonium groups, THPC@TCNF membranes exhibited excellent antibacterial property against B. subtilis, a typical Gram-positive bacterium presenting in oily wastewater. This work provides a simple method to endow nanocellulose membrane with high permeate flux and antibacterial property.