Fabrication of sustainable organic solvent nanofiltration membranes using cellulose–chitosan biopolymer blends

Membrane technologies have emerged as a promising alternative to energy-intensive separation processes in various industrial sectors. To address the sustainability challenge associated with the fabrication of separation membranes, a paradigm shift from the use of petrochemical-based raw materials to greener biobased sources is highly desired. In this study, blends of cellulose — as a plant-based material — and chitosan — obtained from shrimp farming waste and used as a biomass material — were investigated for the fabrication of oil and solvent-resistant nanofiltration membranes. The structural, thermal, mechanical, and morphological properties of the prepared membranes were characterized. Molecular simulations were performed to study the fractional free volume and interaction energy among membrane constituents. Adjusting the cellulose–chitosan ratio allowed fine-tuning the molecular sieving properties of the membranes, which exhibited outstanding separation performance and chemical stability even in harsh solvents, such as polar aprotic solvents, at the maximum temperature of 100 °C. Cellulose membranes containing 25 wt% chitosan achieved the lowest molecular weight cutoff value of 413 g mol−1 and a permeance of 24 L m−2 h−1 bar−1 in acetonitrile. The membranes showed stable separation performance over 7 days of continuous cross-flow nanofiltration. Moreover, the cellulose membranes blended with 10–25 wt% chitosan showed decreased water permeance from 52 to 38 L m−2 h−1 bar−1 and increased oil-removal efficiency from 73.8% to 98.6%. Furthermore, the membranes successfully underwent biodegradation, confirming their potential to close the loop of the sustainable lifecycle of membranes from cradle to grave. Simultaneously tackling waste while generating value-added product by converting waste biomass into solvent-resistant nanofiltration membranes using green solvents. [Display omitted] •Oil and solvent-resistant nanofiltration membranes were prepared using a polymer blend.•Cellulose and chitosan blends were processed using green solvents at ambient conditions.•Membranes showed excellent separation performance and stable long-term continuous filtration.•Molecular sieving properties of membranes were fine-tuned by adjusting the cellulose–chitosan ratio.•Biopolymer-based membranes exhibited biodegradability in an enzymatic solution within few days.