Ethylenediamine-Enhanced Graphene Oxide Nanofibrous Composite Membranes for NMMO/Water Separation via Pervaporation

Recovering N-methylmorpholine N-oxide (NMMO), the cellulose solvent used in Lyocell fiber production, from aqueous mixtures is challenging due to azeotrope formation. Pervaporation offers advantages over conventional separation methods but requires membranes with high selectivity and flux. A kind of thin-film nanofibrous composite (TFNC) membranes is fabricated by depositing ethylenediamine-modified graphene oxide (EGO) onto electrospun polyacrylonitrile (PAN) substrates via layer-by-layer assembly, followed by interfacial polymerization (IP) of a polyamide (PA) selective layer. The EGO interlayer serves dual functions: its abundant amine groups provide nucleation sites for uniform PA layer formation, reducing defects, while exhibiting preferential affinity for NMMO that enhances selectivity. After optimizing EGO loading, ethylenediamine concentration, and polymerization time, the membranes exhibit a well-defined Turing structure and achieve a permeation flux of 840 g/(m 2 h) with 99.7 wt% water in the permeate for 50 wt% NMMO/water mixtures at 75°C. The membranes maintain stable performance during 48-h continuous operation without NMMO thermal decomposition. These results demonstrate that TFNC membranes with functionalized GO interlayers provide an effective approach for NMMO recovery in Lyocell production.