Construction of highly permeable organic solvent nanofiltration membrane via β-cyclodextrin assisted interfacial polymerization

As the key of organic solvent nanofiltration (OSN) technology, OSN membranes could effectively retain small molecules with molecular weight between 200 and 1000 Dalton (Da), but they still face some problems such as low solvent permeance. In this work, we fabricated a poly(amide-ester) selective layer on polyimide substrate surface by introducing β-cyclodextrin (β-CD) into the aqueous phase solution to assist the interfacial polymerization reaction between m-phenylenediamine (MPD) and trimesoyl chloride (TMC), followed by cross-linking and solvent activation treatment. Thus, we successfully fabricated a kind of thin film composite (TFC) membrane with high selective permeability for OSN. We emphasized that extra-low contents were employed for both MPD and β-CD, which were 0.05 wt% and 50 mg L⁻¹, respectively. The effect of β-CD content on the pore size, surface shape, surface hydrophilicity, surface chemistry, filtration performance, as well as durability performance of the OSN membrane was studied in depth. β-CD endows the selective layer with better hydrophilicity and larger pore size. The optimized OSN membrane possesses a Rhodamine B (RDB, 479 Da) rejection of 99.2 % and an ethanol permeance of 70.6 L m⁻² h⁻¹ MPa⁻¹. Furthermore, the optimized OSN membrane remains above 99 % RDB rejection after being immersed in DMF at 25 °C for 1000 h, which demonstrates its superb solvent resistance. Additionally, the optimized OSN membrane exhibits outstanding long-time performance and possesses a rejection of 98 % for Jacobsen catalyst during more than 106 h semi-continuous filtration using Jacobsen catalyst/ethyl acetate solution as feed, indicating its vast potential in the recovery of catalyst.