Nonwoven Membrane Supports from Renewable Resources: Bamboo Fiber Reinforced Poly(Lactic Acid) Composites

Abstract

Membrane separation has been widely recognized as an energy-efficient technology with a rapidly growing market. However, such growth raises concerns about sustainability due to current fabrication methods that employ toxic solvents and nondegradable petroleum-based polymers. The focus of tackling these challenges has been on the active layer of membranes via renewable materials, while the equally important membrane supports are yet to turn green. Herein we report the fabrication of sustainable, biodegradable, nonwoven composite membrane supports made from three renewable materials: bamboo fiber, poly(lactic acid) (PLA), and dimethyl carbonate. The biobased membrane supports exhibited a porous structure (porosity of 0.719 ± 0.132) with tensile strengths (32.7-73.3 MPa) comparable to conventional materials, such as polypropylene. The microstructure and porosity of the supports were revealed by laser scanning confocal microscopy. The increase in bamboo content resulted in increased mechanical stability, decreased swelling, and enhanced permeance, up to 1068 ± 32 L m-2 h-1 bar-1 in water. The long-term chemical stability of membrane supports was verified in 19 of the 25 organic solvents screened. In particular, they were found to be stable in some conventional and emerging green polar aprotic solvents including Cyrene, 2-methyltetrahydrofuran, γ-valerolactone, and propylene carbonate. Stable cross-flow filtration performance over 2 weeks was successfully demonstrated. The results demonstrated that the bamboo/PLA membrane supports could provide a sustainable alternative for conventional membrane backing materials by eliminating the need for petroleum-based nondegradable polymers and toxic solvents.