Efficient and recyclable ultra-thin diameter polyacrylonitrile nanofiber membrane: Selective adsorption of cationic dyes

Membrane separation is a promising technique for the effective removal of dyes from dyeing wastewater resulting from the textile, leather, and paper industries. Herein, we successfully prepared a new symmetrical and self-supporting reconstituted polyacrylonitrile (re-uPAN) membrane by a simple and general method combined island-in-sea bicomponent electrospinning and reconstitution. The simple preparing procedure allows the re-uPAN membranes to retain the chemical structure and dye-absorbing property of the original nanofibers and simultaneously to gain distinct porous and self-supporting features. Such features further endow the potential application of re-uPAN membrane in the effective removal of dyes from wastewater. As a model system, we prepared an optimized re-uPAN membrane with a mass of 12 mg, which showed an average pure water flux of 63.4 L/m2h at 1 bar and a surface porosity of around 30%. The re-uPAN membrane was then used to remove dyes, giving a removal ratio of 100% when the concentration of dye is below 30 mg/L and an absorption capacity of 816.5 mg/m2. The re-uPAN membranes also showed a distinct selectivity of absorbing cationic dyes, which could be potentially used for dye separation. The good mechanical property and self-supporting feature make the re-uPAN membrane be easily recycled. The re-uPAN membrane could well maintain its adsorption capacity even after ten cycles of separation. The generality and simplicity of our re-uPAN membrane-making method pave a new way for preparing membrane, which shows great potentials of being applied in wastewater treatment, nanotechnology, and separation technology.