Electrospun Poly(vinylalcohol)/Chitosan NanofibersEmbedded with a CuO–GO Nanocomposite for pH-Sensitive Adsorptionof Heavy Metal Ions and Organic Dyes

The study reports on the development of innovative hierarchical hybrid nanofibers for the efficient removal of cationic heavy metals and dyes from wastewater. The successful electrospinning of poly­(vinyl alcohol) (PVA) and chitosan (CS) in combination with biosynthesized copper oxide nanoparticle-doped graphene oxide nanocomposites (CuO–GO NCs) at various ratios produced functional nanofibers. The CuO–GO NC was synthesized with a facile one-step method. The cross-linked nanofibers were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), electron microscopy (SEM and TEM), energy-dispersive X-ray (EDX), and thermogravimetric analysis (TGA). SEM results revealed that electrospun nanofibers displayed defect-free uniform spindle-like morphologies with CuO–GO partially embedded onto nanofibers, having average diameters ranging from 52.53 to 65.57 nm. Further, TEM images reveal that CuO–GO is homogeneously dispersed within the nanofiber structure. The thermal analysis demonstrated that the embedded CuO–GO in nanofibers improved the thermal properties and phase change behavior. The nanofibers with 1 wt % CuO–GO performed excellently with a maximum adsorption capacity of 155.23 mg/g for MB dye and 179.9 mg/g for Pb (II) ions. Moreover, the nanofibers exhibited superior removal efficiencies of 89.81% for Pb­(II) ions and 77.67% for MB dye. The optimal pH values for MB dye and Pb­(II) ion adsorption were determined to be 9.1 and 5.5, respectively. The recycling results demonstrated that the cross-linked nanofiber retained excellent stability and performance after four cycles. In this study, 1 wt % CuO–GO-loaded cross-linked PVA/CS nanofibers showed potential adsorption properties for treating MB and Pb (II) ions, making it suitable for wastewater treatment applications with high efficiency.