Solvent remelted nylon polyamide nanofibrous substrate that enhances thin-film composite membranes for organic solvent nanofiltration

Organic solvent nanofiltration (OSN) as a new paradigm technology could satisfy the rapidly growing demand for small-molecular separation and purification in organic solvent systems. Aiming at two main bottlenecks of weak solvent resistance of traditional polymers and high transfer resistance of traditional phase inverted membrane structures, intrinsic solvent-resistant nylon 6 (PA6) was electrospun into nanofibrous substrates to avoid complex cross-linking and lower the transport resistance. A novel solvent-assisted remelting method was proposed to optimize PA6 nanofibrous substrates: pore size and roughness of substrates were reduced, which would provide an ideal substrate for constructing defect-free selective layer; (2) crystal form of PA6 was transferred from semi-stable γ state to stable α state, leading to 2.5 times enhancement of mechanical strength of membranes. Based on the optimized substrate, a high-performance composite membrane was constructed successfully via interfacial polymerization, displaying high methanol permeability of 9.6 L m⁻² h⁻¹ bar⁻¹ and high rejections for different water-soluble and alcohol-soluble dyes, which indicates a succinct and efficient strategy for designing novel OSN membranes.