Dual-Functional Nanofibrous Membranes Based on Poly(Vinyl Alcohol-Co-Ethylene)/Chitosan/Polydopamine Composites for Efficient Adsorption of Congo Red and Cr(VI)

To address the synergistic removal of Congo Red (CR) and hexavalent chromium (Cr(VI)) from industrial wastewater, this study proposed an “electrospinning-surface modification” strategy. Using poly(vinyl alcohol-co-ethylene) (PVA-co-PE) as the substrate, a dual-functional composite nanofibrous membrane adsorbent (PVA-co-PE/chitosan (CS)/polydopamine (PDA)) was constructed via CS grafting and PDA coating. The structural and physicochemical properties of the PVA-co-PE/CS/PDA NF membranes were characterized by elemental mapping, spectroscopic analyses, and morphological observation, while batch experiments were conducted to investigate the adsorption behavior and key influencing factors. Results showed that the composite membrane exhibited maximum adsorption capacities of 716.9 mg/g for CR and 264.4 mg/g for Cr(VI), with the adsorption process conforming to the Langmuir monolayer adsorption model and pseudo-second-order kinetic model (dominated by chemical adsorption). After four adsorption–desorption cycles, the membrane retained adsorption capacities of 609.3 mg/g for CR and 224.5 mg/g for Cr(VI), demonstrating excellent cyclic stability. With advantages of simple preparation, strong recyclability, and negligible secondary pollution, the proposed composite membrane serves as a novel, efficient adsorbent for the synergistic advanced treatment of organic dyes and heavy metal ions in complex industrial and holds substantial engineering application value.