Self-supported nanoporous lysozyme/nanocellulose membranes for multifunctional wastewater purification

To remove multiple pollutants (such as organic dyes, heavy metal ions, emulsified oil droplets, and toxic chemicals) from water resources, developing membranes with multifunctional separation performances is highly demanded. Herein, self-supported nanocomposite membranes with nanoporous structures were fabricated by integrating positively charged amyloid-like oligomers that were obtained by reducing disulfide bonds of native lysozyme onto the surface of negatively charged nanocelluloses via electrostatic interaction and hydrogen bonding. Lysozyme oligomer not only acted as adhesive to glue cellulose nanofibers prepared by 2,2,6,6-tetramethyl-1- piperidinyloxy oxidation (TEMPO), but also reduced the pore size of the resultant membranes to a precise cut-off size of 3 nm. Benefitting from the multiple functional groups (-OH, –COOH, –SH, –NH2), the resultant nanocomposite membranes could efficiently remove organic dyes, heavy metal ions, bilirubin, oil droplets, and boron from wastewater. Moreover, these membranes showed excellent recyclability, mechanical performance, and acid/alkali resistance. This work provided a fast, economical, and sustainable strategy for the fabrication of multifunctional membranes for wastewater purification from natural resources and renewable nanomaterials.