Facile fabrication of functional xerogel membranes from sodium alginate-chitosan microfibers with low crystallinity through one-step solvent-exchange.

Biomass xerogels with porous structures fabricated in ambient conditions possess great advantages including scalability, biocompatibility, and biodegradability, thus have shown demonstrated potential in various fields. However, disadvantages such as poor moisture resistance, poor mechanical properties, and low production efficiency challenge their practical applications. In this study, microfibers self-assembled from sodium alginate and chitosan are adopted to facilely fabricate biomass porous xerogel membranes with a fast one-step solvent-exchange, which is achieved due to the low crystallinity and small aspect ratio of the microfibers. The structure and properties of the membranes are found closely related to the surface tension of the solvent used for solvent exchange. The xerogel membrane prepared by one-step solvent-exchange to ethanol followed ambient drying exhibits a pore size of ~100 nm, porosity of 71.2 %, tensile strength of 11 MPa, and elongation at break of 7.5 %. The low roughness and high hydrophilicity of the xerogel membrane guarantee its usage as filtration and adsorption membranes. The particle rejection efficiency of the membrane reaches 99.9 % and adsorption capacity of the membrane for methyl blue solution is 43.94 mg/g. This novel strategy using microfibers prepared by the bottom-up method paves the way for the scalable fabrication and wildly application of biomass xerogels.