Poly(vinyl alcohol)-based polyester nanofiltration membranes for fractionation of dye/salt mixtures: Alcoholysis degree matters

Poly(vinyl alcohol) (PVA)-based polyester loose nanofiltration (LNF) membranes present an ideal material for achieving dye/salt separation from dye/salt mixtures. Owing to the intrinsic features of the material, PVA with varying degrees of alcoholysis may exhibit different roles and functions, allowing for performance tailoring in PVA-based LNF membranes. In this work, we have demonstrated a facile approach for regulating the performance of polyester (PE) LNF membranes by tailoring the degree of alcoholysis. Stopped-flow mass spectrometry and various characterization techniques showed that an increase in the degree of alcoholysis accelerates reaction rates, increases reaction heat release, and boosts nanobubble formation during interfacial polymerization. The resulting LNF membrane featuring folds and a dense PE film demonstrated a permeance of 44.9 L m-2h−1 bar−1 and a CR/Na2SO4 selectivity of 240, as well as satisfactory stability, showing dye/salt separation performance superior to that of other LNF membranes. This work provides novel insights into tailoring high-performance LNF membranes for selective salt/dye separation.