ScholarWorks@중앙대학교

초록

This study presents a strategy to fabricate ultrathin poly(vinyl alcohol)/carbon nanotube (PVA/CNT) membranes by combining gravity-guided filler distribution and selective dissolution. During solution casting, carboxyl-functionalized multi-walled CNTs naturally migrate downward under gravity, creating a vertical compositional gradient with a CNT-rich region near the substrate and a CNT-lean surface layer. Mild thermal curing induces interfacial bonding between CNT–COOH and PVA hydroxyl groups. A brief hot-water rinse then selectively removes the loosely crosslinked upper layer, yielding a defect-free selective skin thinner than 1 μm supported by a porous structure. This architecture significantly improves mass transport and selectivity for N-methyl-2-pyrrolidone (NMP) dehydration via pervaporation. The membrane exhibits a separation factor of ∼1.9 × 103 at 30 °C with fluxes up to 0.5 kg m−2 h−1. When the CNT-rich side faces the feed, flux increases to 3.1 kg m−2 h−1 at 70 °C, while maintaining a selectivity above 5.6 × 102. The ultrathin structure enables fast and effective dehydration, concentrating NMP to >99.0 % purity in significantly reduced time compared to conventional membranes. The process avoids the use of additional chemical crosslinkers, relying instead on intrinsic interfacial interactions for stability. This scalable and eco-friendly method provides a new design pathway for high-performance membranes tailored for energy-efficient solvent recovery, particularly in applications such as lithium-ion battery manufacturing and bio-based solvent recycling.

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