Functionalization of Electrospun Poly(vinyl alcohol) (PVA) Nanofiber Membranes for Selective Chemical Capture

Electrospun poly­(vinyl alcohol) (PVA) nanofiber membranes were functionalized by incorporating either poly­(methyl vinyl ether-<i>alt</i>-maleic anhydride) (PMA) to create negative charges, or poly­(hexadimethrine bromide) (PB) and chitosan (CS) to create positive charges on the fiber surface. The functionalized PVA nanofiber membranes were heat-treated at elevated temperatures to impart cross-linking and improve the water-resistance. The optimum heat-treatment temperatures for both PVA/PMA and PVA/PB/CS systems were screened by Fourier transformed infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Formation of cross-linked structure and increased crystallinity were triggered by the heat-treatment. A cationic dye, methylene blue (MB), and an anionic dye, acid red 1 (AR1), were used to represent charged moieties in solution. The surface-charged PVA nanofiber membranes were able to selectively capture counter-charged dye molecules from aqueous solutions. The capture processes obey the pseudo-second-order kinetic model. The capture equilibrium can be well-described by the Langmuir model. Chemically cross-linked PVA/PMA nanofiber membranes exhibited higher strength in capturing counter-charged dyes than physically cross-linked PVA/PB/CS nanofiber membranes. Selective chemical capture studies indicated that, by tailoring the surface, functionalized PVA nanofiber membranes were able to selectively remove charged chemicals with potential applications for purifying mixed liquids and delivering a pure sample for detection in small-scale testing systems