Eco-friendly construction of dye-fouled loose CS/PAN nanofibrous composite membranes for permeability-selectivity anti-trade-off property

Abstract

The wide application of composite nanofiltration membrane is greatly restricted by the “trade-off effect” between selectivity and permeability. In this work the trade-off effect was broken by an eco-friendly construction of loose chitosan (CS) coating layer on highly porous polyacrylonitrile (PAN) electrospun nanofibrous scaffold. The loose CS layer was accomplished by stabilizing CS with anionic dyes fouling to enhance the membrane permeability, because their electrostatic interaction was much weaker than CS membrane crosslinked by traditional chemical crosslinkers. To the best of our knowledge, few researches were reported on the dye-fouled CS nanofiltration membrane. The optimized membranes demonstrated excellent filtration performance for anionic dyes separation with superior permeate flux (˜139.1 L m−2 h−1 at 0.1 MPa) and high rejection (˜99.8%) to direct red 80 (DR80) solution of 100 mg/L, as well as cationic dyes separation (like alcian blue 8GX (AB8GX) with rejection of 99.7%). Besides, the CS-DR80/PAN membranes exhibited excellent long-term durability and antifouling nature due to low surface roughness and high surface hydrophilicity. The superior nanofiltration performance was chiefly attributed to the coordinated effect of two-tier structure: the hydrophilic loose negatively-charged barrier layer and the highly porous PAN nanofibrous scaffold. The loose barrier layer and electrospun PAN nanofibrous substrate can guarantee the high permeability, and the negatively charged membrane surface can assure the high rejection due to Donnan repulsion. This strategy not only abridges the complicated process, but also eliminates use of poisonous and expensive ingredients, which provides an eco-friendly and practical feasibility for textile wastewater treatment.