Co-solvent-modulated polyamide nanofiltration membranes for high-temperature separation

Nanofiltration (NF) membranes show superior ion selectivity, which, however, decreases with temperature owing to excessive pore expansion of the selective layers. Herein, an effective and feasible co -solvent strategy is proposed to improve the thermostability of polyamide NF membranes. The co -solvent systems with low interfacial tension accelerate the interfacial diffusion of aqueous monomers during the interfacial polymerization. Moreover, the enhanced compatibility between the organic phase and the nascent polyamide layer, which is assessed by the Hansen solubility parameters, facilitates the formation of selective layers with high cross-linking degree. The resultant compact selective layers possess enhanced thermostability. The optimized NF membrane exhibits a high permeance of 24.8 L·m −2 ·h −1 ·bar −1 with 98.3% MgSO 4 rejection at 85 °C. The present method shows great potential for preparing thermostable NF membranes.